Patchwork new UDPCP Communication Protocol

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Submitter Stefani Seibold
Date Jan. 11, 2011, 4:48 p.m.
Message ID <1294764515-15356-1-git-send-email-stefani@seibold.net>
Download mbox | patch
Permalink /patch/78414/
State Rejected
Delegated to: David Miller
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Comments

Stefani Seibold - Jan. 11, 2011, 4:48 p.m.
From: Stefani Seibold <stefani@seibold.net>

Changelog:
31.12.2010 first proposal
01.01.2011 code cleanup and fixes suggest by Eric Dumazet
02.01.2011 kick away UDP-Lite support
           change spin_lock_irq into spin_lock_bh
           faster udpcp_release_sock base is now linux-next
02.01.2011 fix camel style fix coding style
           fix types in comments
           add per socket max.
           connection limit (pevents against abuse)
           make udpcp adjustable through /proc/sys/net/ipv4/udpcp_
03.01.2011 remove version info message
           add Documentation/networking/udpcp.txt API description
11.01.2011 fix camel style statistics info structure
           litte bit code clean up

UDPCP is a communication protocol specified by the Open Base Station
Architecture Initiative Special Interest Group (OBSAI SIG). The
protocol is based on UDP and is designed to meet the needs of "Mobile
Communcation Base Station" internal communications. It is widely used by
the major networks infrastructure supplier.

The UDPCP communication service supports the following features:

-Connectionless communication for serial mode data transfer
-Acknowledged and unacknowledged transfer modes
-Retransmissions Algorithm
-Checksum Algorithm using Adler32
-Fragmentation of long messages (disassembly/reassembly) to match to the MTU
 during transport:
-Broadcasting and multicasting messages to multiple peers in unacknowledged
 transfer mode

UDPCP supports application level messages up to 64 KBytes (limited by
16-bit
packet data length field). Messages that are longer than the MTU will be
fragmented to the MTU.

UDPCP provides a reliable transport service that will perform message
retransmissions in case transport failures occur.

A documentation about the UDPCP protocol can be found here:

http://read.pudn.com/downloads76/doc/project/283718/OBSAI/OBSAI/RP1_V2.0.PDF

The code is also a nice example how to implement a fast low latency UDP based
protocol as a kernel socket module.

Due the nature of UDPCP which has no sliding windows support, the latency has
a huge impact. The perfomance increase by implementing as a kernel module is
about the factor 10.

Implementing it in User Space is to slow, due the context switches. Also
the net/sunrpc  approach in the kernel is not faster due the using of
kernel threads which are not better than user space (okay, a little bit because
not switching the MMU).

Handling the UDPCP into the data_ready() bh function is much faster:
- No context switch
- Assembly Multi-Fragment Message is very efficient using skb buffer
  chaining.
- Immediately handling an ack or data message save a lot of latency
- Less memory consuming

The implementation is clean and has absolut no side effects to the network
subsystems so i ask for merge it into linux, mm-tree or linux-next.

The patch is against the current linux git tree

- Stefani

Signed-off-by: Stefani Seibold <stefani@seibold.net>
---
 Documentation/networking/udpcp.txt |   82 +
 include/linux/socket.h             |    9 +-
 include/net/udp.h                  |    1 +
 include/net/udpcp.h                |   47 +
 net/Kconfig                        |    1 +
 net/Makefile                       |    1 +
 net/ipv4/ip_output.c               |    2 +
 net/ipv4/ip_sockglue.c             |    2 +
 net/udpcp/Kconfig                  |   34 +
 net/udpcp/Makefile                 |    5 +
 net/udpcp/udpcp.c                  | 2885 ++++++++++++++++++++++++++++++++++++
 11 files changed, 3066 insertions(+), 3 deletions(-)
 create mode 100644 Documentation/networking/udpcp.txt
 create mode 100644 include/net/udpcp.h
 create mode 100644 net/udpcp/Kconfig
 create mode 100644 net/udpcp/Makefile
 create mode 100644 net/udpcp/udpcp.c
Eric Dumazet - Jan. 11, 2011, 5:01 p.m.
Le mardi 11 janvier 2011 à 17:48 +0100, stefani@seibold.net a écrit :
> From: Stefani Seibold <stefani@seibold.net>
> 
...
> The implementation is clean and has absolut no side effects to the network
> subsystems so i ask for merge it into linux, mm-tree or linux-next.
> 
> The patch is against the current linux git tree
> 
> - Stefani
> 
> Signed-off-by: Stefani Seibold <stefani@seibold.net>
> ---
>  

Reading again UDPCP specs, I find it is IPv4/IPv6 agnostic

You copied IPv4 UDP code, so this only handles IPv4...



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Stefani Seibold - Jan. 11, 2011, 8:50 p.m.
Am Dienstag, den 11.01.2011, 18:01 +0100 schrieb Eric Dumazet:
> Le mardi 11 janvier 2011 à 17:48 +0100, stefani@seibold.net a écrit :
> > From: Stefani Seibold <stefani@seibold.net>
> > 
> ...
> > The implementation is clean and has absolut no side effects to the network
> > subsystems so i ask for merge it into linux, mm-tree or linux-next.
> > 
> > The patch is against the current linux git tree
> > 
> > - Stefani
> > 
> > Signed-off-by: Stefani Seibold <stefani@seibold.net>
> > ---
> >  
> 
> Reading again UDPCP specs, I find it is IPv4/IPv6 agnostic
> 
> You copied IPv4 UDP code, so this only handles IPv4...
> 

Right, but currently there is no need for an IPV6 implementation, non of
our base station provide it and non of our mobile network customers use
it.

If it will be required in the future it will be implemented.


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David Miller - Jan. 11, 2011, 8:52 p.m.
From: Stefani Seibold <stefani@seibold.net>
Date: Tue, 11 Jan 2011 21:50:20 +0100

> Right, but currently there is no need for an IPV6 implementation, non of
> our base station provide it and non of our mobile network customers use
> it.
> 
> If it will be required in the future it will be implemented.

We require that you implement the ipv6 side for the submission right
now.

Long gone are the days when we add ipv4 only implementations of
protocols.
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Eric Dumazet - Jan. 11, 2011, 9:06 p.m.
Le mardi 11 janvier 2011 à 21:50 +0100, Stefani Seibold a écrit :
> Am Dienstag, den 11.01.2011, 18:01 +0100 schrieb Eric Dumazet:
> > Le mardi 11 janvier 2011 à 17:48 +0100, stefani@seibold.net a écrit :
> > > From: Stefani Seibold <stefani@seibold.net>
> > > 
> > ...
> > > The implementation is clean and has absolut no side effects to the network
> > > subsystems so i ask for merge it into linux, mm-tree or linux-next.
> > > 
> > > The patch is against the current linux git tree
> > > 
> > > - Stefani
> > > 
> > > Signed-off-by: Stefani Seibold <stefani@seibold.net>
> > > ---
> > >  
> > 
> > Reading again UDPCP specs, I find it is IPv4/IPv6 agnostic
> > 
> > You copied IPv4 UDP code, so this only handles IPv4...
> > 
> 
> Right, but currently there is no need for an IPV6 implementation, non of
> our base station provide it and non of our mobile network customers use
> it.
> 
> If it will be required in the future it will be implemented.
> 
> 

All I wanted to point out is the implementation you did, using a copy of
code instead of stacked layer, makes this ipv6 a whole rewrite.

Better understand know the implications, before code inclusion.

I understand your code satisfies your immediate needs (and companies
that paid this development), but we should make a step forward in code
reuse.



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Stefani Seibold - Jan. 11, 2011, 9:14 p.m.
Am Dienstag, den 11.01.2011, 12:52 -0800 schrieb David Miller:
> From: Stefani Seibold <stefani@seibold.net>
> Date: Tue, 11 Jan 2011 21:50:20 +0100
> 
> > Right, but currently there is no need for an IPV6 implementation, non of
> > our base station provide it and non of our mobile network customers use
> > it.
> > 
> > If it will be required in the future it will be implemented.
> 
> We require that you implement the ipv6 side for the submission right
> now.
> 
> Long gone are the days when we add ipv4 only implementations of
> protocols.

If nobody need it and no user in the near future out there, why should i
implement this? That is dogmatic only!

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David Miller - Jan. 11, 2011, 9:19 p.m.
From: Stefani Seibold <stefani@seibold.net>
Date: Tue, 11 Jan 2011 22:14:40 +0100

> If nobody need it and no user in the near future out there, why should i
> implement this? That is dogmatic only!

It's a hard requirement, sorry.

And I want you to do it especially because it shows clearly how poor
your implementation is, with all of it's code duplication.

You'll need yet another copy of all of this code to support ipv6.

Please implement this properly, and in doing so the ipv6 support will
be very simple if not trivial.
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Eric Dumazet - Jan. 11, 2011, 9:30 p.m.
Le mardi 11 janvier 2011 à 22:14 +0100, Stefani Seibold a écrit :

> If nobody need it and no user in the near future out there, why should i
> implement this? That is dogmatic only!
> 

Sure !

Problem is linux kernel code is not your own project.

Some community rules must be respected.

You call this dogmatic, you are right, since this makes your life less
easy.

However, for hundred of people working to maintain/improve linux kernel
code, especially in network stacks, this ends in less stress, when a
problem must be located, and fixed.

Note : We are trying to help you, not fighting against you, in the long
term, its a win-win for everybody.



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Stefani Seibold - Jan. 11, 2011, 9:40 p.m.
Am Dienstag, den 11.01.2011, 22:30 +0100 schrieb Eric Dumazet:
> Le mardi 11 janvier 2011 à 22:14 +0100, Stefani Seibold a écrit :
> 
> > If nobody need it and no user in the near future out there, why should i
> > implement this? That is dogmatic only!
> > 
> 
> Sure !
> 
> Problem is linux kernel code is not your own project.
> 
> Some community rules must be respected.
> 
> You call this dogmatic, you are right, since this makes your life less
> easy.
> 

Sorry thats not right, i only want write code for the trash bin.

> However, for hundred of people working to maintain/improve linux kernel
> code, especially in network stacks, this ends in less stress, when a
> problem must be located, and fixed.
> 
> Note : We are trying to help you, not fighting against you, in the long
> term, its a win-win for everybody.
> 
> 

Sure, i know this and i would give you and all other contributers a big
thank you for the review.

But it should also okay, to argues against some proposal which makes
currently no sense.


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Stefani Seibold - Jan. 11, 2011, 9:41 p.m.
Am Dienstag, den 11.01.2011, 13:19 -0800 schrieb David Miller:
> From: Stefani Seibold <stefani@seibold.net>
> Date: Tue, 11 Jan 2011 22:14:40 +0100
> 
> > If nobody need it and no user in the near future out there, why should i
> > implement this? That is dogmatic only!
> 
> It's a hard requirement, sorry.
> 
> And I want you to do it especially because it shows clearly how poor
> your implementation is, with all of it's code duplication.
> 

First it is not so much code duplication. It it less than 20 percent of
the whole code. And most of this code was adapted to the need of the
protocol.

Second, the design is may in your opinion poor. I like it. What is
really poor is the kernel_...() socket functions, which are only simple
wrapper of the system calls without any performance improvement, skb
support and memory saving.

IPv6 would not very hard to implement and will be done if i get an go. 

> You'll need yet another copy of all of this code to support ipv6.
> 
> Please implement this properly, and in doing so the ipv6 support will
> be very simple if not trivial.

The implementation is clean and fast, it has absolut no side effect. It
is save to merge and all requirement was solved.


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Eric Dumazet - Jan. 11, 2011, 9:46 p.m.
Le mardi 11 janvier 2011 à 22:41 +0100, Stefani Seibold a écrit :

> Second, the design is may in your opinion poor. I like it. What is
> really poor is the kernel_...() socket functions, which are only simple
> wrapper of the system calls without any performance improvement, skb
> support and memory saving.
> 

The only thing you want is to have a callback to your own code to
deliver an decapsulated skb to your state machine.

Take a look at other layers on top of UDP

(L2TP comes to mind)



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Stefani Seibold - Jan. 11, 2011, 10:23 p.m.
Am Dienstag, den 11.01.2011, 22:46 +0100 schrieb Eric Dumazet:
> Le mardi 11 janvier 2011 à 22:41 +0100, Stefani Seibold a écrit :
> 
> > Second, the design is may in your opinion poor. I like it. What is
> > really poor is the kernel_...() socket functions, which are only simple
> > wrapper of the system calls without any performance improvement, skb
> > support and memory saving.
> > 
> 
> The only thing you want is to have a callback to your own code to
> deliver an decapsulated skb to your state machine.
> 
> Take a look at other layers on top of UDP
> 
> (L2TP comes to mind)
> 

I have looked on it. And it will not work since UDPCP is UDP. And so
IPPROTO_UDP (17) is still handled by the UDP handler.

Despite this it will also make no sense to rewrite the whole UDP socket
layer.

The only thing i have found with comes near to my requirements is the
rxrpc module, but i see no real different to my solution.


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Patch

diff --git a/Documentation/networking/udpcp.txt b/Documentation/networking/udpcp.txt
new file mode 100644
index 0000000..c850218
--- /dev/null
+++ b/Documentation/networking/udpcp.txt
@@ -0,0 +1,82 @@ 
+UDPCP socket interface programming manual
+-----------------------------------------
+
+The socket interface is a derivate of the UDP sockets. All setsockopt(),
+getsockopt() and ioctl() kernel system calls  which are valid for UDP
+sockets should work on UDPCP sockets. There are some extensions to the
+sockopt and ioctl interface for the UDPCP sockets.
+
+Include the C header file <net/udpcp.h> to use the UDPCP socket options
+and ioctl calls.
+
+A UDPCP can be opened with socket(PF_INET, SOCK_DGRAM, PF_UDPCP). All
+operation which are valid for UDP sockets can also performed with UDPCP
+sockets.
+
+sockopt interface
+-----------------
+
+The level parameter for the UDPCP socket is SOL_UDPCP, where the
+following options are defined:
+
+- UDPCP_OPT_TRANSFER_MODE
+  Set default transfer mode. The optval is one of the following:
+   UDPCP_NOACK: no ACK for the transmitted message is requiered
+   UDPCP_ACK: a ACK for each transmitted message fragment is requiered
+   UDPCP_SINGLE_ACK: only a ACK for the last transmitted message fragment
+   is requiered
+
+- UDPCP_OPT_CHECKSUM_MODE
+  Set the default checksum mode. The optval is one of the following:
+   UDPCP_NOCHECKSUM: no checksum for the transmitted message is required
+   UDPCP_CHECKSUM: a checksum test for the transmitted message is required
+
+- UDPCP_OPT_TX_TIMEOUT
+  The timeout for a awaited ACK in milliseconds.
+  The optval should between >= 1 and max. UDPCP_MAX_WAIT_SEC * 1000
+
+- UDPCP_OPT_RX_TIMEOUT
+  Timeout for a outstanding incoming message fragment in milliseconds.
+  The optval should between >= 1 and max. UDPCP_MAX_WAIT_SEC * 1000
+
+- UDPCP_OPT_MAXTRY
+  The number of tries to send a message fragment.
+  The optval should between >= 1 and <= 10
+
+- UDPCP_OPT_OUTSTANDING_ACKS
+  The number of outstanding acks.
+  The optval should between >=1 and <= 255
+
+All optlen parameters are int's. Therefor the optlen should be sizeof(optlen).
+
+The values UDPCP_NOACK, UDPCP_ACK, UDPCP_SINGLE_ACK, UDPCP_NOCHECKSUM
+and UDPCP_CHECKSUM can also passed as control message with sendmsg(). For
+details look at the manual page for sendmsg().
+
+ioctl interface
+---------------
+
+For UDPCP sockets there are the following request commands defined:
+
+- UDPCP_IOCTL_GET_STATISTICS
+  This command returns the statistics of the socket in a struct
+  udpcp_statistics. The address of this struct must be passed as third
+  argument.
+
+- UDPCP_IOCTL_RESET_STATISTICS
+  This command resets the statistics of the socket
+
+- UDPCP_IOCTL_SYNC 
+  This command waits until all message fragments are transmitted. If the
+  third argument is not zero, this is the max. timeout value in
+  milliseconds, otherwise this call can block indefinitely.
+
+sysctl interface
+----------------
+
+/proc/sys/net/ipv4/udpcp/udpcp_max_connections
+  Maximum UDPCP connections per socket
+
+/proc/sys/net/ipv4/udpcp/udpcp_debug
+  kernel lock debug messages enabled or not
+
diff --git a/include/linux/socket.h b/include/linux/socket.h
index 5f65f14..496be02 100644
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -169,7 +169,7 @@  struct ucred {
 #define AF_DECnet	12	/* Reserved for DECnet project	*/
 #define AF_NETBEUI	13	/* Reserved for 802.2LLC project*/
 #define AF_SECURITY	14	/* Security callback pseudo AF */
-#define AF_KEY		15      /* PF_KEY key management API */
+#define AF_KEY		15	/* PF_KEY key management API */
 #define AF_NETLINK	16
 #define AF_ROUTE	AF_NETLINK /* Alias to emulate 4.4BSD */
 #define AF_PACKET	17	/* Packet family		*/
@@ -191,7 +191,8 @@  struct ucred {
 #define AF_PHONET	35	/* Phonet sockets		*/
 #define AF_IEEE802154	36	/* IEEE802154 sockets		*/
 #define AF_CAIF		37	/* CAIF sockets			*/
-#define AF_MAX		38	/* For now.. */
+#define AF_UDPCP	38	/* UDPCP sockets		*/
+#define AF_MAX		39	/* For now.. */
 
 /* Protocol families, same as address families. */
 #define PF_UNSPEC	AF_UNSPEC
@@ -201,7 +202,7 @@  struct ucred {
 #define PF_AX25		AF_AX25
 #define PF_IPX		AF_IPX
 #define PF_APPLETALK	AF_APPLETALK
-#define	PF_NETROM	AF_NETROM
+#define PF_NETROM	AF_NETROM
 #define PF_BRIDGE	AF_BRIDGE
 #define PF_ATMPVC	AF_ATMPVC
 #define PF_X25		AF_X25
@@ -232,6 +233,7 @@  struct ucred {
 #define PF_PHONET	AF_PHONET
 #define PF_IEEE802154	AF_IEEE802154
 #define PF_CAIF		AF_CAIF
+#define PF_UDPCP	AF_UDPCP
 #define PF_MAX		AF_MAX
 
 /* Maximum queue length specifiable by listen.  */
@@ -305,6 +307,7 @@  struct ucred {
 #define SOL_RDS		276
 #define SOL_IUCV	277
 #define SOL_CAIF	278
+#define SOL_UDPCP	279
 
 /* IPX options */
 #define IPX_TYPE	1
diff --git a/include/net/udp.h b/include/net/udp.h
index bb967dd..82c95a7 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -47,6 +47,7 @@  struct udp_skb_cb {
 	} header;
 	__u16		cscov;
 	__u8		partial_cov;
+	__u8            udpcp_flag;
 };
 #define UDP_SKB_CB(__skb)	((struct udp_skb_cb *)((__skb)->cb))
 
diff --git a/include/net/udpcp.h b/include/net/udpcp.h
new file mode 100644
index 0000000..dd85efe
--- /dev/null
+++ b/include/net/udpcp.h
@@ -0,0 +1,47 @@ 
+/* Definitions for UDPCP sockets. */
+
+#ifndef __LINUX_IF_UDPCP
+#define __LINUX_IF_UDPCP
+
+#include "linux/ioctl.h"
+
+#define UDPCP_MAX_MSGSIZE	65487
+
+#define UDPCP_MAX_WAIT_SEC	60
+
+#define UDPCP_OPT_TRANSFER_MODE		0
+#define UDPCP_OPT_CHECKSUM_MODE		1
+#define UDPCP_OPT_TX_TIMEOUT		2
+#define UDPCP_OPT_RX_TIMEOUT		3
+#define UDPCP_OPT_MAXTRY		4
+#define UDPCP_OPT_OUTSTANDING_ACKS	5
+
+#define UDPCP_NOACK		0
+#define UDPCP_ACK		1
+#define UDPCP_SINGLE_ACK	2
+#define UDPCP_NOCHECKSUM	3
+#define UDPCP_CHECKSUM		4
+
+#define UDPCP_IOC_MAGIC  251
+
+#define UDPCP_IOCTL_GET_STATISTICS \
+	_IOR(UDPCP_IOC_MAGIC, 0x01, struct udpcp_statistics *)
+#define UDPCP_IOCTL_RESET_STATISTICS \
+	_IO(UDPCP_IOC_MAGIC, 0x02)
+#define UDPCP_IOCTL_SYNC \
+	_IOR(UDPCP_IOC_MAGIC, 0x03, unsigned long)
+
+struct udpcp_statistics {
+	unsigned int tx_msgs;		/* Num of transmitted messages */
+	unsigned int rx_msgs;		/* Num of received messages */
+	unsigned int tx_nodes;		/* Num of transmitter nodes */
+	unsigned int rx_nodes;		/* Num of receiver nodes */
+	unsigned int tx_timeout;	/* Num of unsuccessful transmissions */
+	unsigned int rx_timeout;	/* Num of partial message receptions */
+	unsigned int tx_retries;	/* Num of resends */
+	unsigned int rx_discarded_frags;/* Num of discarded fragments */
+	unsigned int crc_errors;	/* Num of crc errors detected */
+};
+
+#endif
+
diff --git a/net/Kconfig b/net/Kconfig
index ad0aafe..6a12c12 100644
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -300,6 +300,7 @@  source "net/rfkill/Kconfig"
 source "net/9p/Kconfig"
 source "net/caif/Kconfig"
 source "net/ceph/Kconfig"
+source "net/udpcp/Kconfig"
 
 
 endif   # if NET
diff --git a/net/Makefile b/net/Makefile
index a3330eb..388a582 100644
--- a/net/Makefile
+++ b/net/Makefile
@@ -70,3 +70,4 @@  obj-$(CONFIG_WIMAX)		+= wimax/
 obj-$(CONFIG_DNS_RESOLVER)	+= dns_resolver/
 obj-$(CONFIG_CEPH_LIB)		+= ceph/
 obj-$(CONFIG_BATMAN_ADV)	+= batman-adv/
+obj-$(CONFIG_UDPCP)		+= udpcp/
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 04c7b3b..41f9276 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -1084,6 +1084,7 @@  error:
 	IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
 	return err;
 }
+EXPORT_SYMBOL(ip_append_data);
 
 ssize_t	ip_append_page(struct sock *sk, struct page *page,
 		       int offset, size_t size, int flags)
@@ -1340,6 +1341,7 @@  error:
 	IP_INC_STATS(net, IPSTATS_MIB_OUTDISCARDS);
 	goto out;
 }
+EXPORT_SYMBOL(ip_push_pending_frames);
 
 /*
  *	Throw away all pending data on the socket.
diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index 3948c86..310369c 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -226,6 +226,7 @@  int ip_cmsg_send(struct net *net, struct msghdr *msg, struct ipcm_cookie *ipc)
 	}
 	return 0;
 }
+EXPORT_SYMBOL(ip_cmsg_send);
 
 
 /* Special input handler for packets caught by router alert option.
@@ -369,6 +370,7 @@  void ip_local_error(struct sock *sk, int err, __be32 daddr, __be16 port, u32 inf
 	if (sock_queue_err_skb(sk, skb))
 		kfree_skb(skb);
 }
+EXPORT_SYMBOL(ip_local_error);
 
 /*
  *	Handle MSG_ERRQUEUE
diff --git a/net/udpcp/Kconfig b/net/udpcp/Kconfig
new file mode 100644
index 0000000..a58c1b0
--- /dev/null
+++ b/net/udpcp/Kconfig
@@ -0,0 +1,34 @@ 
+#
+# UDPCP protocol
+#
+
+config UDPCP
+	tristate "UDPCP Communication Protocol"
+	depends on INET
+	---help---
+	  UDPCP is a communication protocol specified by the Open Base Station
+	  Architecture Initiative Special Interest Group (OBSAI SIG). The
+	  protocol is based on UDP and is designed to meet the needs of "Mobile
+	  Communcation Base Station" internal communications.
+
+	  The UDPCP communication service supports the following features:
+
+          -Connectionless communication for serial mode data transfer
+          -Acknowledged and unacknowledged transfer modes
+          -Retransmissions Algorithm
+          -Checksum Algorithm using Adler32
+          -Fragmentation of long messages (disassembly/reassembly) to
+           match to the MTU during transport:
+          -Broadcasting and multicasting messages to multiple peers in
+           unacknowledged transfer mode
+
+          UDPCP supports application level messages up to 64 KBytes (limited
+          by 16-bit packet data length field). Messages that are longer than the
+          MTU will be fragmented to the MTU.
+
+          UDPCP provides a reliable transport service that will perform message
+          retransmissions in case transport failures occur.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called udpcp.
+
diff --git a/net/udpcp/Makefile b/net/udpcp/Makefile
new file mode 100644
index 0000000..37f87c5
--- /dev/null
+++ b/net/udpcp/Makefile
@@ -0,0 +1,5 @@ 
+#
+# Makefile for UDPCP support code.
+#
+
+obj-$(CONFIG_UDPCP) += udpcp.o
diff --git a/net/udpcp/udpcp.c b/net/udpcp/udpcp.c
new file mode 100644
index 0000000..82e20a6
--- /dev/null
+++ b/net/udpcp/udpcp.c
@@ -0,0 +1,2885 @@ 
+/*
+ * UDPCP communication protocol
+ *
+ * Copyright (C) 2010 Stefani Seibold <stefani@seibold.net>
+ * in order of NSN Ulm/Germany
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ */
+
+#include <net/xfrm.h>
+#include <net/protocol.h>
+#include <net/ip.h>
+#include <net/udp.h>
+#include <net/inet_common.h>
+#include <linux/zutil.h>
+#include <linux/module.h>
+#include <linux/proc_fs.h>
+#include <linux/spinlock.h>
+#include <linux/errqueue.h>
+#include <linux/atomic.h>
+
+#include <net/udpcp.h>
+
+/*
+ * UDPCP Protocol default parameters
+ */
+#define UDPCP_TX_TIMEOUT	100	/* milliseconds */
+#define UDPCP_RX_TIMEOUT	1000	/* milliseconds */
+#define UDPCP_TX_MAXTRY		5
+#define UDPCP_OUTSTANDING_ACKS	1
+
+/*
+ * UDPCP Protocol definitions
+ */
+#define UDPCP_MSG_TYPE_BIT		14
+#define UDPCP_PROTOCOL_VERSION_BIT	11
+#define UDPCP_NO_ACK_BIT		10
+#define UDPCP_CHECKSUM_BIT		9
+#define UDPCP_SINGLE_ACK_BIT		8
+#define UDPCP_DUPLICATE_BIT		7
+
+#define UDPCP_MSG_TYPE_MASK		(3 << UDPCP_MSG_TYPE_BIT)
+#define UDPCP_PROTOCOL_MASK		(7 << UDPCP_PROTOCOL_VERSION_BIT)
+
+#define UDPCP_MSG_TYPE_DATA		(1 << UDPCP_MSG_TYPE_BIT)
+#define UDPCP_MSG_TYPE_ACK		(2 << UDPCP_MSG_TYPE_BIT)
+#define UDPCP_PROTOCOL_VERSION_2	(2 << UDPCP_PROTOCOL_VERSION_BIT)
+
+#define UDPCP_NO_ACK_FLAG		(1 << UDPCP_NO_ACK_BIT)
+#define UDPCP_CHECKSUM_FLAG		(1 << UDPCP_CHECKSUM_BIT)
+#define UDPCP_SINGLE_ACK_FLAG		(1 << UDPCP_SINGLE_ACK_BIT)
+#define UDPCP_DUPLICATE_FLAG		(1 << UDPCP_DUPLICATE_BIT)
+
+/*
+ * helper macros
+ */
+#define list_to_udpcpdest(d) container_of(d, struct udpcp_dest, list)
+#define list_to_udpcpsock(d) container_of(d, struct udpcp_sock, udpcplist)
+
+#define UDPCP_HDRSIZE	(sizeof(struct udpcphdr)-sizeof(struct udphdr))
+
+#define RX_NODE	1
+#define TX_NODE	2
+
+/*
+ * name of the /proc entry
+ */
+#define UDPCP_PROC	"driver/udpcp"
+
+/*
+ * UDPCP message header
+ */
+struct udpcphdr {
+	struct udphdr udphdr;
+	__be32 chksum;
+	__be16 msginfo;
+	u8 fragamount;
+	u8 fragnum;
+	__be16 msgid;
+	__be16 length;
+};
+
+/*
+ * UDPCP destination descriptor
+ *
+ * For each communication address an individual destination descriptor will
+ * be create.
+ *
+ * The fields has the following meanings:
+ *
+ * list:		link list: part of udpcp_sock.destlist
+ * xmit:		messages fragments to be transmit
+ * tx_time:		timestamp of the last transmitted message fragment
+ * rx_time:		timestamp ot the last received message fragment
+ * tx_timeout:		statistic use only: number of transmit timeout
+ * rx_timeout:		statistic use only: number of receive timeout
+ * tx_retries:		statistic use only: number of transmit retries
+ * rx_discarded_frags:	statistic use only: number of discarded messages
+ * xmit_wait:		message fragment which is waiting for an ACK
+ * xmit_last:		last fragment transmitted
+ * recv_msg:		first fragment of the received message
+ * recv_last:		last fragment of the received message
+ * lastmsg:		last messages fragment header received
+ * ipc:			linux internal ipc cookie
+ * fl:			flow/routing information
+ * rt:			routing entry currently used for this destination
+ * addr:		ipv4 destination address
+ * port:		destination port number
+ * msgid:		current message id for outgoing data messages
+ * use_flag:		statistic use only: flag for dest using TX and/or RX
+ * insync:		flag for protocol synchronization
+ * ackmode;		ack mode for the current assembled message
+ * chkmode;		checksum mode for the current assembled message
+ * try:			current number of retries xmit_wait message
+ * acks:		number of outstandig ack's
+ */
+struct udpcp_dest {
+	struct list_head list;
+	struct sk_buff_head xmit;
+	unsigned long tx_time;
+	unsigned long rx_time;
+	u32 tx_timeout;
+	u32 rx_timeout;
+	u32 tx_retries;
+	u32 rx_discarded_frags;
+	struct sk_buff *xmit_wait;
+	struct sk_buff *xmit_last;
+	struct sk_buff *recv_msg;
+	struct sk_buff *recv_last;
+	struct udpcphdr lastmsg;
+	struct ipcm_cookie ipc;
+	struct flowi fl;
+	struct rtable *rt;
+	__be32 addr;
+	__be16 port;
+	u16 msgid;
+	u8 use_flag;
+	u8 insync;
+	u8 ackmode;
+	u8 chkmode;
+	u8 try;
+	u8 acks;
+};
+
+/*
+ * UDPCP socket descriptor
+ *
+ * For each opened socket individual socket descriptor will
+ * be created
+ *
+ * The fields has the following meanings:
+ *
+ * udpsock:		UDP socket has to be the first member of udpcp_sock
+ * assembly:		messages fragments currently assembled
+ * assembly_len:	current length of the assembled message
+ * assembly_dest:	current destination assembled
+ * wq:			wait queue for UDPCP_IOCTL_SYNC
+ * destlist:		head of destination descriptors link list
+ * udpcplist:		link list: part of udpcp_list
+ * timer:		timeout handler
+ * stat:		statistics for this socket
+ * pending:		number of pending messages fragment in the queues
+ * tx_timeout:		transmit timeout in jiffies
+ * rx_timeout:		receive timeout in jiffies
+ * udp_data_ready:	original data_ready handler for this socket
+ * ackmode:		default ack mode
+ * chkmode:		default checksum mode
+ * maxtry:		max. number of resends
+ * acks:		max. number of outstandig ack's
+ * timeout:		flag for unhandled timeout
+ */
+struct udpcp_sock {
+	struct udp_sock udpsock;
+	struct sk_buff_head assembly;
+	u32 assembly_len;
+	struct udpcp_dest *assembly_dest;
+	wait_queue_head_t wq;
+	struct list_head destlist;
+	struct list_head udpcplist;
+	struct timer_list timer;
+	struct udpcp_statistics stat;
+	u32 pending;
+	unsigned long tx_timeout;
+	unsigned long rx_timeout;
+	u32 connections;
+	void (*udp_data_ready) (struct sock *sk, int bytes);
+	u8 ackmode;
+	u8 chkmode;
+	u8 maxtry;
+	u8 acks;
+	u8 timeout;
+};
+
+/* head of struct udpcp_sock.udpcplist link list */
+static struct list_head udpcp_list;
+
+/* spinlock for race free access to the static variables */
+static spinlock_t udpcp_lock;
+
+/* debug flag, set != 0 to enable debug */
+static int udpcp_max_connections = 64;
+
+/* /proc/sys/net/ipv4/udpcp_* table */
+static struct ctl_table_header *udpcp_ctl_table;
+
+/* debug flag, set != 0 to enable debug */
+static int debug;
+
+/* overall UDPCP statistics */
+static atomic_t udpcp_tx_msgs;
+static atomic_t udpcp_rx_msgs;
+static atomic_t udpcp_tx_nodes;
+static atomic_t udpcp_rx_nodes;
+static atomic_t udpcp_tx_timeout;
+static atomic_t udpcp_rx_timeout;
+static atomic_t udpcp_tx_retries;
+static atomic_t udpcp_rx_discarded_frags;
+static atomic_t udpcp_crc_errors;
+
+module_param(debug, int, 0);
+MODULE_PARM_DESC(debug, "Debug enabled or not");
+
+module_param(udpcp_max_connections, int, 0);
+MODULE_PARM_DESC(udpcp_max_connections, "maximum connections per sockets");
+
+static int zero;
+
+static struct ctl_table ipv4_udpcp_table[] = {
+	{
+		.procname	= "udpcp_max_connections",
+		.data		= &udpcp_max_connections,
+		.maxlen		= sizeof(udpcp_max_connections),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &zero
+	},
+	{
+		.procname	= "udpcp_debug",
+		.data		= &debug,
+		.maxlen		= sizeof(debug),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &zero
+	},
+	{ }
+};
+
+#ifdef CONFIG_PROC_FS
+/*
+ * Handle /proc/driver/udpcp
+ *
+ * Show the statistics information
+ */
+static int udpcp_proc(char *page, char **start, off_t off, int count, int *eof,
+		      void *data)
+{
+	int len;
+
+	len = snprintf(page, count,
+		       "txMsgs:          %u\n"
+		       "rxMsgs:          %u\n"
+		       "txNodes:         %u\n"
+		       "rxNodes:         %u\n"
+		       "txTimeout:       %u\n"
+		       "rxTimeout:       %u\n"
+		       "txRetries:       %u\n"
+		       "rxDiscaredFrags: %u\n"
+		       "crcErrors:       %u\n",
+			atomic_read(&udpcp_tx_msgs),
+			atomic_read(&udpcp_rx_msgs),
+			atomic_read(&udpcp_tx_nodes),
+			atomic_read(&udpcp_rx_nodes),
+			atomic_read(&udpcp_tx_timeout),
+			atomic_read(&udpcp_rx_timeout),
+			atomic_read(&udpcp_tx_retries),
+			atomic_read(&udpcp_rx_discarded_frags),
+			atomic_read(&udpcp_crc_errors)
+		);
+
+	if (len <= off)
+		return 0;
+
+	len -= off;
+
+	if (len > count)
+		return count;
+
+	return len;
+}
+#endif
+
+/*
+ * Helper for the UDPCP header from a socket buffer
+ */
+static inline struct udpcphdr *udpcp_hdr(const struct sk_buff *skb)
+{
+	return (struct udpcphdr *)skb_transport_header(skb);
+}
+
+/*
+ * Helper for conversion a basic socket into a UDPCP socket
+ */
+static inline struct udpcp_sock *udpcp_sk(const struct sock *sk)
+{
+	return (struct udpcp_sock *)sk;
+}
+
+/*
+ * Dump the transport data of a socket buffer
+ */
+static inline void dump_data(struct sk_buff *skb, unsigned int max)
+{
+	unsigned int i;
+	unsigned char *data;
+	int data_len;
+
+	data = skb_transport_header(skb) + sizeof(struct udpcphdr);
+	data_len = skb_tail_pointer(skb) - data;
+
+	pr_debug(" data: ");
+
+	if (!data_len) {
+		pr_cont("<none>\n");
+		return;
+	}
+
+	if (max > data_len)
+		max = data_len;
+
+	for (i = 0; i < max; i++)
+		pr_cont("%02x ", data[i]);
+
+	if (data_len > max)
+		pr_cont("...");
+	pr_cont("\n");
+}
+
+/*
+ * Dump and decode a msginfo value
+ */
+static inline void dump_msginfo(u16 msginfo)
+{
+	pr_debug(" msginfo:0x%04x (", msginfo);
+
+	pr_cont("PCKT:");
+	switch (msginfo & UDPCP_MSG_TYPE_MASK) {
+	case UDPCP_MSG_TYPE_DATA:
+		pr_cont("DATA");
+		break;
+	case UDPCP_MSG_TYPE_ACK:
+		pr_cont("ACK");
+		break;
+	default:
+		pr_cont("UNKNOWN");
+		break;
+	}
+	pr_cont(" VER:%d",
+	       (msginfo & UDPCP_PROTOCOL_MASK) >> UDPCP_PROTOCOL_VERSION_BIT);
+
+	if (msginfo & UDPCP_NO_ACK_FLAG)
+		pr_cont(" NO_ACK");
+	if (msginfo & UDPCP_CHECKSUM_FLAG)
+		pr_cont(" CHECKSUM");
+	if (msginfo & UDPCP_SINGLE_ACK_FLAG)
+		pr_cont(" SINGLE_ACK");
+	if (msginfo & UDPCP_DUPLICATE_FLAG)
+		pr_cont(" DUPLICATE");
+	pr_cont(")\n");
+}
+
+/*
+ * Dump and decode a UDPCP message fragment
+ */
+static void dump_msg(const char *action, struct sk_buff *skb, __be32 saddr,
+		     __be32 daddr)
+{
+	struct udpcphdr *uh = udpcp_hdr(skb);
+
+	pr_debug("udpcp: %s (%lu)\n", action, jiffies);
+
+	pr_debug(" src:0x%08x:%d dst:0x%08x:%d fraglen:%d\n",
+	       saddr, uh->udphdr.source, daddr, uh->udphdr.dest, skb->len);
+
+	pr_debug(" fragamount:%u fragnum:%u msgid:%u%s"
+		 " length:%u checksum:0x%08x\n",
+	       uh->fragamount, uh->fragnum, ntohs(uh->msgid),
+	       (!uh->msgid) ? "(Sync)" : "", ntohs(uh->length),
+	       ntohl(uh->chksum)
+	    );
+
+	dump_msginfo(ntohs(uh->msginfo));
+	dump_data(skb, 16);
+}
+
+/*
+ * Create a new destination descriptor for the given IPV4 address and port
+ */
+static struct udpcp_dest *new_dest(struct sock *sk, __be32 addr, __be16 port)
+{
+	struct udpcp_dest *dest;
+	struct udpcp_sock *usk = udpcp_sk(sk);
+
+	if (usk->connections >= udpcp_max_connections)
+		return NULL;
+
+	dest = kzalloc(sizeof(*dest), sk->sk_allocation);
+
+	if (dest) {
+		usk->connections++;
+		skb_queue_head_init(&dest->xmit);
+		dest->addr = addr;
+		dest->port = port;
+		dest->ackmode = UDPCP_ACK;
+		list_add_tail(&dest->list, &usk->destlist);
+	}
+
+	return dest;
+}
+
+/*
+ * Lookup for a destination descriptor for the given IPV4 address and port
+ */
+static struct udpcp_dest *__find_dest(struct sock *sk, __be32 addr, __be16 port)
+{
+	struct udpcp_dest *dest;
+	struct list_head *p;
+	struct udpcp_sock *usk = udpcp_sk(sk);
+
+	list_for_each(p, &usk->destlist) {
+		dest = list_to_udpcpdest(p);
+
+		if ((dest->addr == addr) && (dest->port == port))
+			return dest;
+	}
+	return NULL;
+}
+
+/*
+ * Lookup for a destination descriptor and create a new one if no
+ * descriptor was found.
+ */
+static struct udpcp_dest *find_dest(struct sock *sk, __be32 addr, __be16 port)
+{
+	struct udpcp_dest *dest = __find_dest(sk, addr, port);
+
+	if (!dest)
+		dest = new_dest(sk, addr, port);
+
+	return dest;
+}
+
+/*
+ * Calculate udp checksum, mostly stolen from udp stack
+ */
+static void udpcp_do_csum(struct sock *sk, struct sk_buff *skb,
+			  struct udpcp_dest *dest)
+{
+	struct flowi *fl = &dest->fl;
+	struct udphdr *uh = udp_hdr(skb);
+	__wsum csum = 0;
+	unsigned short len = ntohs(uh->len);
+
+	if (sk->sk_no_check == UDP_CSUM_NOXMIT) {
+		skb->ip_summed = CHECKSUM_NONE;
+		return;
+	}
+	if (skb->ip_summed == CHECKSUM_PARTIAL) {
+		/* UDP hardware csum */
+		skb->csum_start = skb_transport_header(skb) - skb->head;
+		skb->csum_offset = offsetof(struct udphdr, check);
+		uh->check =
+		    ~csum_tcpudp_magic(fl->fl4_src, fl->fl4_dst, len,
+				       sk->sk_protocol, 0);
+		return;
+	}
+	csum = csum_partial(uh, sizeof(struct udpcphdr), 0);
+	csum = csum_add(csum, skb->csum);
+
+	/* add protocol-dependent pseudo-header */
+	uh->check =
+	    csum_tcpudp_magic(fl->fl4_src, fl->fl4_dst, len, sk->sk_protocol,
+			      csum);
+	if (uh->check == 0)
+		uh->check = CSUM_MANGLED_0;
+}
+
+/*
+ * Fetch data from kernel space and fill in checksum if needed.
+ */
+static int ip_reply_glue_bits(void *dptr, char *to, int offset,
+			      int len, int odd, struct sk_buff *skb)
+{
+	__wsum csum;
+
+	csum = csum_partial_copy_nocheck(dptr+offset, to, len, 0);
+	skb->csum = csum_block_add(skb->csum, csum, odd);
+	return 0;
+}
+
+/*
+ * Send an ack for a received data message fragment
+ *
+ * If the argument duplicate is true a ACK with UDPCP_DUPLICATE_FLAG set will
+ * be send
+ */
+static void udpcp_send_ack(struct sock *sk, struct sk_buff *skb,
+			   struct udpcp_dest *dest, int duplicate)
+{
+	struct inet_sock *inet = inet_sk(sk);
+	struct udpcphdr *uh = udpcp_hdr(skb);
+	struct rtable *rt = NULL;
+	__wsum csum;
+	struct ipcm_cookie ipc;
+	struct udpcphdr rep;
+
+	memset(&rep, 0, sizeof(rep));
+
+	/* Swap the send and the receive ports. */
+	rep.udphdr.source = uh->udphdr.dest;
+	rep.udphdr.dest = uh->udphdr.source;
+	rep.udphdr.len = htons(sizeof(struct udpcphdr));
+
+	rep.msginfo = htons(UDPCP_MSG_TYPE_ACK |
+			    UDPCP_NO_ACK_FLAG |
+			    UDPCP_SINGLE_ACK_FLAG | UDPCP_PROTOCOL_VERSION_2);
+	if (duplicate)
+		rep.msginfo |= htons(UDPCP_DUPLICATE_FLAG);
+	else
+		memcpy(&dest->lastmsg, uh, sizeof(dest->lastmsg));
+	rep.msgid = uh->msgid;
+	rep.fragamount = uh->fragamount;
+	rep.fragnum = uh->fragnum;
+	rep.length = 0;
+	rep.chksum = 0;
+	if (ntohs(uh->msginfo) & UDPCP_CHECKSUM_FLAG) {
+		u8 *data;
+		u32 data_len;
+
+		data = (u8 *) &rep + sizeof(struct udphdr);
+		data_len = sizeof(struct udpcphdr)-sizeof(struct udphdr);
+
+		rep.msginfo |= htons(UDPCP_CHECKSUM_FLAG);
+		rep.chksum = htonl(zlib_adler32(1, data, data_len));
+	}
+
+	if (unlikely(debug)) {
+		struct sk_buff tmp;
+
+		tmp.len = ntohs(rep.udphdr.len);
+		tmp.head = tmp.transport_header = tmp.data = (void *)&rep;
+		tmp.tail = tmp.head + tmp.len;
+
+		dump_msg("ack msg", &tmp, ip_hdr(skb)->daddr,
+			 ip_hdr(skb)->saddr);
+	}
+
+	csum = csum_tcpudp_nofold(ip_hdr(skb)->daddr,
+				      ip_hdr(skb)->saddr,
+				      sizeof(rep), sk->sk_protocol, 0);
+
+	ipc.addr = dest->addr;
+	ipc.opt = NULL;
+	ipc.tx_flags = 0;
+
+	{
+		struct flowi fl = {
+			.nl_u = { .ip4_u = {
+						.daddr = ipc.addr,
+						.saddr = ip_hdr(skb)->daddr,
+						.tos = RT_TOS(ip_hdr(skb)->tos)
+					      }
+			},
+			.uli_u = { .ports = {
+						.sport = udp_hdr(skb)->dest,
+						.dport = udp_hdr(skb)->source
+				       }
+			},
+			.proto = sk->sk_protocol,
+		};
+		security_skb_classify_flow(skb, &fl);
+		if (ip_route_output_key(sock_net(sk), &rt, &fl))
+			return;
+	}
+
+	inet->tos = ip_hdr(skb)->tos;
+	sk->sk_priority = skb->priority;
+	sk->sk_protocol = ip_hdr(skb)->protocol;
+	sk->sk_bound_dev_if = 0;
+	ip_append_data(sk, ip_reply_glue_bits, &rep, sizeof(rep),
+				0, &ipc, &rt, MSG_DONTWAIT);
+	skb = skb_peek(&sk->sk_write_queue);
+	if (skb) {
+		*((__sum16 *)skb_transport_header(skb) +
+		  offsetof(struct udphdr, check) / 2) =
+			csum_fold(csum_add(skb->csum, csum));
+		skb->ip_summed = CHECKSUM_NONE;
+		ip_push_pending_frames(sk);
+	}
+
+	ip_rt_put(rt);
+
+	UDP_INC_STATS_BH(sock_net(sk), UDP_MIB_OUTDATAGRAMS, 0);
+}
+
+/*
+ * Pass a UDPCP skb buffer to the ip stack and send it
+ */
+static int udpcp_send_skb(struct sock *sk, struct sk_buff *skb,
+			  struct udpcp_dest *dest, struct ip_options *opt)
+{
+	int err;
+
+	skb_dst_set(skb, dst_clone(&dest->rt->dst));
+
+	err = ip_build_and_send_pkt(skb, sk, dest->fl.fl4_src,
+					dest->fl.fl4_dst, opt);
+
+	if (!err)
+		UDP_INC_STATS_USER(sock_net(sk), UDP_MIB_OUTDATAGRAMS, 0);
+	return err;
+}
+
+/*
+ * Release a routing table entry if no packet will be assembled
+ */
+static void udpcp_dst_release(struct udpcp_sock *usk, struct udpcp_dest *dest)
+{
+	if (usk->assembly_dest != dest) {
+		dst_release(&dest->rt->dst);
+		dest->rt = NULL;
+	}
+}
+
+/*
+ * Return true if the passed skb socket buffer is the last in the list
+ */
+static inline bool skb_is_eoq(const struct sk_buff_head *list,
+			      const struct sk_buff *skb)
+{
+	return (skb->next == (struct sk_buff *)list);
+}
+
+/*
+ * Arm the timeout handler for the socket
+ */
+static void udpcp_timer(struct sock *sk, unsigned long timeout)
+{
+	struct udpcp_sock *usk = udpcp_sk(sk);
+
+	mod_timer(&usk->timer, timeout);
+}
+
+/*
+ * Decrement the socket pending counter and wakeup a waiting UDPCP_IOCTL_SYNC
+ */
+static inline void udpcp_dec_pending(struct sock *sk)
+{
+	struct udpcp_sock *usk = udpcp_sk(sk);
+
+	if (!--usk->pending) {
+		if (waitqueue_active(&usk->wq))
+			wake_up_interruptible(&usk->wq);
+	}
+}
+
+/*
+ * Returns true is the passed message fragment is the last fragment
+ */
+static inline int udpcp_is_last_frag(struct udpcphdr *uh)
+{
+	return uh->fragamount == uh->fragnum + 1;
+}
+
+/*
+ * Transmit data message fragments
+ */
+static int _udpcp_xmit(struct sock *sk, struct udpcp_dest *dest)
+{
+	struct udpcp_sock *usk = udpcp_sk(sk);
+	struct sk_buff *skb = NULL;
+	struct sk_buff *skbc;
+	struct udpcphdr *uh;
+	int err = 0;
+
+	if (dest->acks >= usk->acks)
+		goto out;
+
+	if (!dest->xmit_last) {
+		/*
+		 * handle data message fragments without an ack
+		 */
+		while ((skb = skb_peek(&dest->xmit))) {
+			uh = udpcp_hdr(skb);
+
+			if (!(ntohs(uh->msginfo) & UDPCP_NO_ACK_FLAG))
+				break;
+			if (udpcp_is_last_frag(uh)) {
+				usk->stat.tx_msgs++;
+				atomic_inc(&udpcp_tx_msgs);
+			}
+			skb_unlink(skb, &dest->xmit);
+			udpcp_dec_pending(sk);
+			if (unlikely(debug))
+				dump_msg("send msg", skb, dest->fl.fl4_src,
+					 dest->fl.fl4_dst);
+			err = udpcp_send_skb(sk, skb, dest,
+						(struct ip_options *)skb->cb);
+			if (err) {
+				kfree_skb(skb);
+				skb = NULL;
+				break;
+			}
+		}
+		dest->xmit_wait = skb;
+	} else {
+		/*
+		 * handle next data message fragment waiting for an ack
+		 */
+		uh = udpcp_hdr(dest->xmit_last);
+
+		if (udpcp_is_last_frag(uh))
+			goto out;
+
+		/*
+		 * get next data message fragment
+		 */
+		skb = dest->xmit_last->next;
+	}
+
+	/*
+	 * send all data message fragment till the first which must be acked
+	 */
+	while (skb) {
+		skbc = skb_clone(skb, sk->sk_allocation);
+
+		if (!skbc)
+			break;
+
+		if (unlikely(debug))
+			dump_msg("send msg", skbc, dest->fl.fl4_src,
+				 dest->fl.fl4_dst);
+		err = udpcp_send_skb(sk, skbc, dest,
+					(struct ip_options *)skb->cb);
+		if (err) {
+			kfree_skb(skbc);
+			break;
+		}
+
+		uh = udpcp_hdr(skb);
+
+		if (!(ntohs(uh->msginfo) & UDPCP_SINGLE_ACK_FLAG)
+		    || udpcp_is_last_frag(uh)) {
+			dest->xmit_last = skb;
+
+			if (++dest->acks >= usk->acks || udpcp_is_last_frag(uh))
+				break;
+		}
+
+		skb = skb_is_eoq(&dest->xmit, skb) ? NULL : skb->next;
+	}
+
+out:
+	if (skb_queue_empty(&dest->xmit))
+		udpcp_dst_release(usk, dest);
+
+	return err;
+}
+
+/*
+ * Transmit data message fragments and rearm the timeout handler if necessary
+ */
+static int udpcp_xmit(struct sock *sk, struct udpcp_dest *dest)
+{
+	int ret = _udpcp_xmit(sk, dest);
+
+	if (dest->xmit_wait) {
+		struct udpcp_sock *usk = udpcp_sk(sk);
+
+		dest->tx_time = jiffies;
+		if (!timer_pending(&usk->timer))
+			udpcp_timer(sk, dest->tx_time + usk->tx_timeout);
+	}
+	return ret;
+}
+
+/*
+ * Queue the assembled message fragment into the transmit queue
+ */
+static void udpcp_queue_xmit(struct sock *sk, struct udpcp_dest *dest,
+			     u8 ackmode, u8 chkmode)
+{
+	struct udpcp_sock *usk = udpcp_sk(sk);
+	struct udpcphdr *uh;
+	struct sk_buff *skb;
+	u8 fragamount;
+	u8 fragnum;
+	unsigned short msginfo;
+	struct flowi *fl = &dest->fl;
+
+	msginfo = UDPCP_MSG_TYPE_DATA | UDPCP_PROTOCOL_VERSION_2;
+	switch (ackmode) {
+	case UDPCP_NOACK:
+		msginfo |= UDPCP_NO_ACK_FLAG;
+		break;
+	case UDPCP_SINGLE_ACK:
+		msginfo |= UDPCP_SINGLE_ACK_FLAG;
+		break;
+	case UDPCP_ACK:
+	default:
+		break;
+	}
+	switch (chkmode) {
+	case UDPCP_NOCHECKSUM:
+		break;
+	case UDPCP_CHECKSUM:
+	default:
+		msginfo |= UDPCP_CHECKSUM_FLAG;
+		break;
+	}
+
+	fragamount = skb_queue_len(&usk->assembly);
+
+	udpcp_sk(sk)->pending += fragamount;
+
+	for (fragnum = 0; fragnum != fragamount; fragnum++) {
+		unsigned char *data;
+		int data_len;
+
+		skb = skb_dequeue(&usk->assembly);
+		uh = udpcp_hdr(skb);
+
+		/*
+		 * setup a UDPCP header
+		 */
+		uh->chksum = 0;
+		uh->msginfo = htons(msginfo);
+		uh->fragnum = fragnum;
+		uh->fragamount = fragamount;
+		uh->msgid = htons(dest->msgid);
+		uh->length = htons(usk->assembly_len);
+
+		data = skb_transport_header(skb) + sizeof(struct udphdr);
+		data_len = skb_tail_pointer(skb) - data;
+
+		if (chkmode == UDPCP_CHECKSUM)
+			uh->chksum = htonl(zlib_adler32(1, data, data_len));
+		/*
+		 * create a UDP header
+		 */
+		uh->udphdr.source = fl->fl_ip_sport;
+		uh->udphdr.dest = fl->fl_ip_dport;
+		uh->udphdr.len = htons(sizeof(struct udphdr) + data_len);
+		uh->udphdr.check = 0;
+
+		/*
+		 * create UDP checksum
+		 */
+		udpcp_do_csum(sk, skb, dest);
+
+		/*
+		 * add to xmit queue
+		 */
+		skb_queue_tail(&dest->xmit, skb);
+	}
+
+	dest->msgid++;
+	usk->assembly_len = 0;
+	usk->assembly_dest = NULL;
+}
+
+/*
+ * Remove all data message fragments of the first message from the transmit
+ * queue all fragments will be merged together
+ */
+static struct sk_buff *udpcp_dequeue_msg(struct sock *sk,
+					 struct udpcp_dest *dest)
+{
+	struct sk_buff *msg;
+	struct sk_buff *skb;
+	struct sk_buff **next;
+	struct udpcphdr *uh;
+
+	msg = skb_dequeue(&dest->xmit);
+	if (!msg)
+		return NULL;
+	skb_orphan(msg);
+
+	uh = udpcp_hdr(msg);
+	if (!uh->msgid) {
+		/*
+		 * sync message
+		 */
+		kfree_skb(msg);
+		return NULL;
+	}
+
+	skb_pull(msg, sizeof(struct udpcphdr));
+	if (udpcp_is_last_frag(uh))
+		return msg;
+
+	next = &skb_shinfo(msg)->frag_list;
+	for (;;) {
+		skb = skb_dequeue(&dest->xmit);
+		if (!skb)
+			break;
+		skb_orphan(skb);
+		uh = udpcp_hdr(skb);
+		skb_pull(msg, sizeof(struct udpcphdr));
+		msg->len += skb->len;
+		msg->data_len += skb->len;
+		*next = skb;
+		if (udpcp_is_last_frag(uh))
+			break;
+		next = &skb->next;
+	}
+	return msg;
+}
+
+static void udpcp_flush_err(struct sock *sk, struct udpcp_dest *dest)
+{
+	struct inet_sock *inet = inet_sk(sk);
+	struct udpcp_sock *usk = udpcp_sk(sk);
+
+	if (!inet->recverr) {
+		skb_queue_purge(&dest->xmit);
+	} else {
+		struct sock_exterr_skb *serr;
+		struct iphdr *iph;
+		struct sk_buff *skb;
+
+		while (!skb_queue_empty(&dest->xmit)) {
+			skb = udpcp_dequeue_msg(sk, dest);
+			if (!skb)
+				continue;
+
+			if (unlikely(debug))
+				dump_msg("flush outgoing message", skb,
+					 dest->fl.fl4_src, dest->fl.fl4_dst);
+
+			skb_push(skb, sizeof(struct iphdr));
+			skb_reset_network_header(skb);
+			iph = ip_hdr(skb);
+			iph->daddr = dest->rt->rt_dst;
+
+			serr = SKB_EXT_ERR(skb);
+			serr->ee.ee_errno = EPROTO;
+			serr->ee.ee_origin = SO_EE_ORIGIN_LOCAL;
+			serr->ee.ee_type = 0;
+			serr->ee.ee_code = 0;
+			serr->ee.ee_pad = 0;
+			serr->ee.ee_info = 0;
+			serr->ee.ee_data = 0;
+			serr->addr_offset = (u8 *) &iph->daddr -
+						skb_network_header(skb);
+			serr->port = dest->fl.fl_ip_dport;
+
+			skb_reset_transport_header(skb);
+			skb_pull(skb, sizeof(struct iphdr));
+
+			/*
+			 * set a flag for UDPCP message
+			 */
+			UDP_SKB_CB(skb)->udpcp_flag = 1;
+
+			/*
+			 * pass the dequeued message to the error queue of the
+			 * socket
+			 */
+			skb_set_owner_r(skb, sk);
+			skb_queue_tail(&sk->sk_error_queue, skb);
+			if (!sock_flag(sk, SOCK_DEAD)) {
+				if (usk->udp_data_ready)
+					usk->udp_data_ready(sk, skb->len);
+			}
+		}
+	}
+
+	dest->xmit_wait = 0;
+	dest->xmit_last = 0;
+	dest->try = 0;
+	dest->acks = 0;
+
+	usk->pending = 0;
+	if (waitqueue_active(&usk->wq))
+		wake_up_interruptible(&usk->wq);
+}
+
+/*
+ * Purge the current incoming data message
+ */
+static void udpcp_purge_incoming(struct sock *sk, struct udpcp_dest *dest)
+{
+	struct udpcp_sock *usk = udpcp_sk(sk);
+
+	if (dest->recv_last) {
+		u32 fragnum = udpcp_hdr(dest->recv_last)->fragnum + 1;
+
+		dest->rx_discarded_frags += fragnum;
+		usk->stat.rx_discarded_frags += fragnum;
+		atomic_add(fragnum, &udpcp_rx_discarded_frags);
+
+		dest->lastmsg.msgid = 0;
+
+		if (unlikely(debug))
+			dump_msg("purge incoming message", dest->recv_msg,
+				 dest->fl.fl4_src, dest->fl.fl4_dst);
+	}
+
+	kfree_skb(dest->recv_msg);
+	dest->recv_msg = 0;
+	dest->recv_last = 0;
+}
+
+/*
+ * Resend all data message fragments to the one which is currently waiting for
+ * an ack
+ */
+static int udpcp_resend(struct sock *sk, struct udpcp_dest *dest)
+{
+	struct sk_buff *skb;
+	struct sk_buff *skbc;
+	struct udpcp_sock *usk = udpcp_sk(sk);
+	int err;
+
+	if (++dest->try >= usk->maxtry) {
+		dest->insync = 0;
+		udpcp_flush_err(sk, dest);
+		udpcp_purge_incoming(sk, dest);
+		udpcp_dst_release(usk, dest);
+		return 0;
+	}
+
+	dest->tx_retries++;
+	usk->stat.tx_retries++;
+	atomic_inc(&udpcp_tx_retries);
+
+	if (!dest->xmit_last) {
+		_udpcp_xmit(sk, dest);
+	} else {
+		skb = dest->xmit_wait;
+
+		for (;;) {
+			skbc = skb_clone(skb, sk->sk_allocation);
+
+			if (skbc == NULL)
+				break;
+
+			if (unlikely(debug))
+				dump_msg("resend msg", skbc, dest->fl.fl4_src,
+					 dest->fl.fl4_dst);
+			err = udpcp_send_skb(sk, skbc, dest,
+						(struct ip_options *)skb->cb);
+			if (err) {
+				kfree_skb(skbc);
+				break;
+			}
+
+			if (skb == dest->xmit_last) {
+				_udpcp_xmit(sk, dest);
+				break;
+			}
+
+			skb = skb->next;
+		}
+	}
+	dest->tx_time = jiffies;
+
+	return 1;
+}
+
+/*
+ * Handle udpcp timeout
+ */
+static void udpcp_handle_timeout(struct sock *sk)
+{
+	struct udpcp_dest *dest;
+	struct list_head *p;
+	struct udpcp_sock *usk = udpcp_sk(sk);
+	int wflag = 0;
+	unsigned long t = jiffies + UDPCP_MAX_WAIT_SEC * HZ + 1;
+
+	usk->timeout = 0;
+
+	/*
+	 * walk through all destinations
+	 */
+	list_for_each(p, &usk->destlist) {
+		dest = list_to_udpcpdest(p);
+
+		if (dest->xmit_wait) {
+			if (time_is_before_eq_jiffies
+			    (dest->tx_time + usk->tx_timeout)) {
+				/*
+				 * transmit timeout expired
+				 */
+				if (unlikely(debug))
+					dump_msg("send timeout",
+						 dest->xmit_wait,
+						 dest->fl.fl4_src,
+						 dest->fl.fl4_dst);
+				if (udpcp_resend(sk, dest) == 0) {
+					dest->tx_timeout++;
+					usk->stat.tx_timeout++;
+					atomic_inc(&udpcp_tx_timeout);
+					goto check_incoming;
+				}
+				wflag = 1;
+			}
+			if (time_before(dest->tx_time + usk->tx_timeout, t)) {
+				/*
+				 * calculate new timeout timer value
+				 */
+				t = dest->tx_time + usk->tx_timeout;
+				wflag = 1;
+			}
+		}
+check_incoming:
+		if (dest->recv_msg) {
+			if (time_is_before_eq_jiffies
+			    (dest->rx_time + usk->rx_timeout)) {
+				/*
+				 * receive timeout occurred
+				 */
+				if (unlikely(debug))
+					dump_msg("receive timeout",
+						 dest->recv_last,
+						 dest->fl.fl4_src,
+						 dest->fl.fl4_dst);
+				udpcp_purge_incoming(sk, dest);
+				dest->rx_timeout++;
+				usk->stat.rx_timeout++;
+				atomic_inc(&udpcp_rx_timeout);
+			} else
+			if (time_before(dest->rx_time + usk->rx_timeout, t)) {
+				/*
+				 * calculate new timeout timer value
+				 */
+				t = dest->rx_time + usk->rx_timeout;
+				wflag = 1;
+			}
+		}
+	}
+	/*
+	 * restart timer if necessary
+	 */
+	if (wflag)
+		udpcp_timer(sk, t);
+}
+
+/*
+ * Timeout function
+ */
+static void udpcp_timeout(unsigned long data)
+{
+	struct sock *sk = (struct sock *)data;
+	struct udpcp_sock *usk = udpcp_sk(sk);
+
+	bh_lock_sock(sk);
+	if (!sock_owned_by_user(sk)) {
+		udpcp_handle_timeout(sk);
+	} else {
+		/*
+		 * bad, cannot handle the timeout because the socket is in use
+		 * set flag for unhandled timeout and rearm the timer
+		 */
+		usk->timeout = 1;
+		udpcp_timer(sk, jiffies + 1);
+	}
+	bh_unlock_sock(sk);
+}
+
+/*
+ * Handle timeout if an the unhandled timeout flag is set
+ */
+static inline void check_timeout(struct sock *sk)
+{
+	struct udpcp_sock *usk = udpcp_sk(sk);
+
+	while (usk->timeout) {
+		lock_sock(sk);
+		while (usk->timeout)
+			udpcp_handle_timeout(sk);
+		release_sock(sk);
+	}
+}
+
+/*
+ * Release the socket lock and test for unhandled timeouts
+ */
+static inline void udpcp_release_sock(struct sock *sk)
+{
+	struct udpcp_sock *usk = udpcp_sk(sk);
+
+	while (usk->timeout)
+		udpcp_handle_timeout(sk);
+	release_sock(sk);
+	check_timeout(sk);
+}
+
+/*
+ * Parse sendmsg() control message
+ */
+static int udpcp_cmsg_send(struct msghdr *msg, u8 * ackmode, u8 * chkmode)
+{
+	struct cmsghdr *cmsg;
+
+	for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg)) {
+		if (!CMSG_OK(msg, cmsg))
+			return -EINVAL;
+		if (cmsg->cmsg_level != SOL_UDPCP)
+			continue;
+		switch (cmsg->cmsg_type) {
+		case UDPCP_NOACK:
+		case UDPCP_ACK:
+		case UDPCP_SINGLE_ACK:
+			*ackmode = cmsg->cmsg_type;
+			break;
+		case UDPCP_CHECKSUM:
+		case UDPCP_NOCHECKSUM:
+			*chkmode = cmsg->cmsg_type;
+			break;
+		default:
+			return -EINVAL;
+		}
+	}
+	return 0;
+}
+
+/*
+ * Validate a skb buffer
+ */
+static int udpcp_validate_skb(struct sk_buff *skb)
+{
+	if (skb->next) {
+		pr_err("udpcp: unexpected skb_buff->next != NULL\n");
+		BUG();
+		return 1;
+	}
+	if (skb_shinfo(skb)->frag_list) {
+		pr_err("udpcp: unexpected skb_shinfo(skb)->frag_list != NULL\n");
+		BUG();
+		return 1;
+	}
+	return 0;
+}
+
+/*
+ * Split a message into fragments and store it into the assemble queue
+ * mostly stolen from UDP stack
+ */
+static int udpcp_data(struct sock *sk, struct udpcp_dest *dest,
+		      struct iovec *from, int length, unsigned int flags)
+{
+	struct udpcp_sock *usk = udpcp_sk(sk);
+	struct inet_sock *inet = inet_sk(sk);
+	struct sk_buff *skb;
+	struct ipcm_cookie *ipc = &dest->ipc;
+	struct ip_options *opt = ipc->opt;
+	int hh_len;
+	int exthdrlen;
+	int mtu;
+	int copy;
+	int err;
+	int offset = 0;
+	unsigned int maxfraglen, fragheaderlen;
+	int csummode = CHECKSUM_NONE;
+	int transhdrlen = sizeof(struct udpcphdr);
+	struct rtable *rt = dest->rt;
+
+	if (opt && sizeof(skb->cb) < optlength(opt)) {
+		err = -EFAULT;
+		goto error;
+	}
+
+	usk->assembly_len += length;
+	usk->assembly_dest = dest;
+
+	if (usk->assembly_len > UDPCP_MAX_MSGSIZE) {
+		ip_local_error(sk, EMSGSIZE, rt->rt_dst, dest->fl.fl_ip_dport,
+				usk->assembly_len);
+		err = -EMSGSIZE;
+		goto error;
+	}
+
+	mtu = (inet->pmtudisc == IP_PMTUDISC_PROBE) ?
+		rt->dst.dev->mtu : dst_mtu(rt->dst.path);
+	sk->sk_sndmsg_page = NULL;
+	sk->sk_sndmsg_off = 0;
+	exthdrlen = rt->dst.header_len;
+	length += exthdrlen;
+	transhdrlen += exthdrlen;
+
+	hh_len = LL_RESERVED_SPACE(rt->dst.dev);
+
+	fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
+	maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen;
+
+	if (rt->dst.dev->features & NETIF_F_V4_CSUM && !exthdrlen)
+		csummode = CHECKSUM_PARTIAL;
+
+	skb = skb_peek_tail(&usk->assembly);
+	if (skb) {
+		unsigned int off;
+
+		off = skb->len;
+
+		copy = mtu - skb->len;
+		if (copy > length)
+			copy = length;
+
+		if (copy > 0 &&
+		    ip_generic_getfrag(
+		     from, skb_put(skb, copy), 0, copy, off, skb) < 0) {
+			__skb_trim(skb, off);
+			err = -EFAULT;
+			goto error;
+		}
+		length -= copy;
+		offset += copy;
+
+		if (!length)
+			return 0;
+	}
+
+	do {
+		char *data;
+		unsigned int datalen;
+		unsigned int fraglen;
+		unsigned int alloclen;
+
+		length += transhdrlen;
+		/*
+		 * If remaining data exceeds the mtu,
+		 * we know we need more fragment(s).
+		 */
+		datalen = length;
+		if (datalen > mtu - fragheaderlen)
+			datalen = maxfraglen - fragheaderlen;
+		fraglen = datalen + fragheaderlen;
+
+		if ((flags & MSG_MORE)
+		    && !(rt->dst.dev->features & NETIF_F_SG))
+			alloclen = mtu;
+		else
+			alloclen = fraglen;
+
+		alloclen += rt->dst.trailer_len + hh_len + 15;
+
+		udpcp_release_sock(sk);
+		skb = sock_alloc_send_skb(sk, alloclen,
+					(flags & MSG_DONTWAIT), &err);
+		lock_sock(sk);
+		if (skb == NULL)
+			goto error;
+
+		if (udpcp_validate_skb(skb)) {
+			kfree_skb(skb);
+
+			goto error;
+		}
+
+		/*
+		 * Fill in the control structures
+		 */
+		skb->ip_summed = csummode;
+		skb->csum = 0;
+		skb_reserve(skb, hh_len);
+
+		/*
+		 * Find where to start putting bytes.
+		 */
+		data = skb_put(skb, fraglen);
+		skb_set_network_header(skb, exthdrlen);
+		skb->transport_header = (skb->network_header + fragheaderlen);
+		data += fragheaderlen;
+
+		copy = datalen - transhdrlen;
+
+		if (copy > 0 &&
+		  ip_generic_getfrag(
+		   from, data + transhdrlen, offset, copy, 0, skb) < 0) {
+			err = -EFAULT;
+			kfree_skb(skb);
+			goto error;
+		}
+
+		offset += copy;
+		length -= datalen;
+
+		if (ipc->opt)
+			memcpy(skb->cb, &ipc->opt, optlength(opt));
+
+		skb_pull(skb, fragheaderlen);
+		skb_queue_tail(&usk->assembly, skb);
+	} while (length > 0);
+
+	return 0;
+error:
+	skb_queue_purge(&usk->assembly);
+	usk->assembly_len = 0;
+
+	IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS);
+	return err;
+}
+
+/*
+ * This function will be called by send(), sento() and sendmsg()
+ */
+static int udpcp_sendmsg(struct kiocb *iocb, struct sock *sk,
+			 struct msghdr *msg, size_t len)
+{
+	struct inet_sock *inet = inet_sk(sk);
+	struct udpcp_sock *usk = udpcp_sk(sk);
+	struct ipcm_cookie *ipc;
+	struct rtable *rt = NULL;
+	int free = 0;
+	int connected = 0;
+	__be32 daddr, faddr, saddr;
+	__be16 dport;
+	u8 tos;
+	int err = 0;
+	int corkreq = usk->udpsock.corkflag || msg->msg_flags & MSG_MORE;
+	struct udpcp_dest *dest;
+
+	if (len > UDPCP_MAX_MSGSIZE)
+		return -EMSGSIZE;
+
+	/*
+	 * Check the flags.
+	 */
+	if (msg->msg_flags & MSG_OOB)
+		return -EOPNOTSUPP;
+
+	/*
+	 * check if socket is binded to a port
+	 */
+	if (!(sk->sk_userlocks & SOCK_BINDPORT_LOCK) || !inet->inet_num)
+		return -ENOTCONN;
+
+	/*
+	 * Get and verify the address.
+	 */
+	if (msg->msg_name) {
+		struct sockaddr_in *usin = (struct sockaddr_in *)msg->msg_name;
+		if (msg->msg_namelen < sizeof(*usin))
+			return -EINVAL;
+		if (usin->sin_family != AF_INET) {
+			if (usin->sin_family != AF_UNSPEC)
+				return -EAFNOSUPPORT;
+		}
+
+		daddr = usin->sin_addr.s_addr;
+		dport = usin->sin_port;
+	} else {
+		if (sk->sk_state != TCP_ESTABLISHED)
+			return -EDESTADDRREQ;
+		daddr = inet->inet_daddr;
+		dport = inet->inet_dport;
+		/* Open fast path for connected socket.
+		   Route will not be used, if at least one option is set.
+		 */
+		connected = 1;
+	}
+
+	if (dport == 0)
+		return -EINVAL;
+
+	dest = find_dest(sk, daddr, dport);
+	if (!dest)
+		return -ENOMEM;
+
+	if (!(dest->use_flag & TX_NODE)) {
+		dest->use_flag |= TX_NODE;
+		usk->stat.tx_nodes++;
+		atomic_inc(&udpcp_tx_nodes);
+	}
+
+	ipc = &dest->ipc;
+
+	if (!skb_queue_empty(&usk->assembly)) {
+		/*
+		 * assembly is ongoing
+		 */
+		lock_sock(sk);
+		if (likely(!skb_queue_empty(&usk->assembly))) {
+			if (usk->assembly_dest != dest) {
+				udpcp_release_sock(sk);
+				return -EUSERS;
+			}
+			ipc->opt =
+			    (struct ip_options *)skb_peek(&usk->assembly)->cb;
+			goto queue_data;
+		}
+		udpcp_release_sock(sk);
+	}
+
+	ipc->addr = inet->inet_saddr;
+	ipc->oif = sk->sk_bound_dev_if;
+
+	dest->ackmode = usk->ackmode;
+	dest->chkmode = usk->chkmode;
+
+	if (msg->msg_controllen) {
+		/*
+		 * handle control message
+		 */
+		err = udpcp_cmsg_send(msg, &dest->ackmode, &dest->chkmode);
+		if (err)
+			return err;
+		err = ip_cmsg_send(sock_net(sk), msg, ipc);
+		if (err)
+			return err;
+		if (ipc->opt)
+			free = 1;
+		connected = 0;
+	}
+
+	if (!ipc->opt)
+		ipc->opt = inet->opt;
+
+	saddr = ipc->addr;
+	ipc->addr = faddr = daddr;
+
+	if (ipc->opt && ipc->opt->srr) {
+		if (!daddr)
+			return -EINVAL;
+		faddr = ipc->opt->faddr;
+		connected = 0;
+	}
+	tos = RT_TOS(inet->tos);
+	if (sock_flag(sk, SOCK_LOCALROUTE) ||
+	    (msg->msg_flags & MSG_DONTROUTE) ||
+	    (ipc->opt && ipc->opt->is_strictroute)) {
+		tos |= RTO_ONLINK;
+		connected = 0;
+	}
+
+	if (ipv4_is_multicast(daddr)) {
+		if (dest->ackmode != UDPCP_NOACK) {
+			err = EOPNOTSUPP;
+			goto out;
+		}
+		if (!ipc->oif)
+			ipc->oif = inet->mc_index;
+		if (!saddr)
+			saddr = inet->mc_addr;
+		connected = 0;
+	}
+
+	lock_sock(sk);
+	rt = dest->rt;
+	if (rt)
+		goto queue_data;
+	udpcp_release_sock(sk);
+
+	/*
+	 * calculate routing
+	 */
+	if (connected)
+		rt = (struct rtable *)sk_dst_check(sk, 0);
+
+	if (rt == NULL) {
+		struct flowi fl = {.oif = ipc->oif,
+			.nl_u = {.ip4_u = {.daddr = faddr,
+					   .saddr = saddr,
+					   .tos = tos} },
+			.proto = sk->sk_protocol,
+			.uli_u = {.ports = {.sport = inet->inet_sport,
+					    .dport = dport} }
+		};
+		struct net *net = sock_net(sk);
+
+		security_sk_classify_flow(sk, &fl);
+		err = ip_route_output_flow(net, &rt, &fl, sk, 1);
+		if (err) {
+			if (err == -ENETUNREACH)
+				IP_INC_STATS_BH(net, IPSTATS_MIB_OUTNOROUTES);
+			goto out;
+		}
+
+		err = -EACCES;
+		if ((rt->rt_flags & RTCF_BROADCAST) &&
+		    !sock_flag(sk, SOCK_BROADCAST))
+			goto out;
+		if (connected)
+			sk_dst_set(sk, dst_clone(&rt->dst));
+	}
+
+	if (msg->msg_flags & MSG_CONFIRM)
+		goto do_confirm;
+back_from_confirm:
+
+	saddr = rt->rt_src;
+	if (!ipc->addr)
+		daddr = ipc->addr = rt->rt_dst;
+
+	lock_sock(sk);
+
+	dest->fl.fl4_dst = daddr;
+	dest->fl.fl_ip_dport = dport;
+	dest->fl.fl4_src = saddr;
+	dest->fl.fl_ip_sport = inet->inet_sport;
+	dest->rt = rt;
+
+queue_data:
+	if (msg->msg_flags & MSG_PROBE)
+		goto release;
+
+	if (!dest->insync && skb_queue_empty(&dest->xmit)) {
+		/*
+		 * if not synced, queue a SYNC message
+		 */
+		err = udpcp_data(sk, dest, NULL, 0, 0);
+		if (err)
+			goto release;
+		dest->msgid = 0;
+		udpcp_queue_xmit(sk, dest, UDPCP_ACK, UDPCP_CHECKSUM);
+	}
+
+	/*
+	 * split message and store it to the assembly queue
+	 */
+	err = udpcp_data(sk, dest, msg->msg_iov, len,
+		       corkreq ? msg->msg_flags | MSG_MORE : msg->msg_flags);
+	if (err)
+		goto release;
+
+	if (!dest->msgid)
+		dest->msgid = 1;
+
+	if (!corkreq) {
+		/*
+		 * message is complete, transfer it from the assembly queue
+		 * into the transmit queue
+		 */
+		udpcp_queue_xmit(sk, dest, dest->ackmode, dest->chkmode);
+		/*
+		 * start transmit if possible
+		 */
+		err = udpcp_xmit(sk, dest);
+	}
+release:
+	udpcp_release_sock(sk);
+out:
+	if (free)
+		kfree(ipc->opt);
+
+	if (!err)
+		return len;
+	/*
+	 * ENOBUFS = no kernel mem, SOCK_NOSPACE = no sndbuf space.  Reporting
+	 * ENOBUFS might not be good (it's not tunable per se), but otherwise
+	 * we don't have a good statistic (IpOutDiscards but it can be too many
+	 * things).  We could add another new stat but at least for now that
+	 * seems like overkill.
+	 */
+	if (err == -ENOBUFS || test_bit(SOCK_NOSPACE, &sk->sk_socket->flags))
+		UDP_INC_STATS_USER(sock_net(sk), UDP_MIB_SNDBUFERRORS, 0);
+	return err;
+
+do_confirm:
+	dst_confirm(&rt->dst);
+	if (!(msg->msg_flags & MSG_PROBE) || len)
+		goto back_from_confirm;
+
+	err = 0;
+	goto out;
+}
+
+/*
+ * Sendpage() is not really implemented
+ */
+static int udpcp_sendpage(struct sock *sk, struct page *page, int offset,
+			  size_t size, int flags)
+{
+	return sock_no_sendpage(sk->sk_socket, page, offset, size, flags);
+}
+
+/*
+ * Release all message fragments of the first in the transmit queue
+ */
+static void udpcp_release_xmit(struct sock *sk, struct udpcp_dest *dest)
+{
+	struct udpcp_sock *usk = udpcp_sk(sk);
+	struct sk_buff *skb;
+	struct udpcphdr *uh;
+
+	for (;;) {
+		skb = skb_dequeue(&dest->xmit);
+
+		uh = udpcp_hdr(skb);
+
+		if (udpcp_is_last_frag(uh) && uh->msgid) {
+			usk->stat.tx_msgs++;
+			atomic_inc(&udpcp_tx_msgs);
+		}
+
+		udpcp_dec_pending(sk);
+
+		kfree_skb(skb);
+		if (skb == dest->xmit_last)
+			break;
+	}
+
+	dest->xmit_wait = 0;
+	dest->xmit_last = 0;
+	dest->try = 0;
+}
+
+/*
+ * Set the sync state
+ */
+static void udpcp_sync(struct sock *sk, struct udpcp_dest *dest)
+{
+	dest->xmit_wait = 0;
+	dest->xmit_last = 0;
+	dest->try = 0;
+	dest->acks = 0;
+	dest->insync = 1;
+}
+
+/*
+ * Returns true if the first message in the transmit queue is a sync message
+ */
+static inline int udpcp_xmit_is_sync(struct udpcp_dest *dest)
+{
+	struct sk_buff *skb = skb_peek(&dest->xmit);
+
+	return skb && !udpcp_hdr(skb)->msgid;
+}
+
+static inline struct udpcphdr *udpcp_ack_scan(struct sk_buff *skb)
+{
+	struct udpcphdr *uh;
+
+	for (;;) {
+		uh = udpcp_hdr(skb);
+
+		if (!(ntohs(uh->msginfo) & UDPCP_SINGLE_ACK_FLAG)
+		    || udpcp_is_last_frag(uh))
+			return uh;
+
+		skb = skb->next;
+	}
+}
+
+/*
+ * Handle an incoming ack
+ */
+static void udpcp_handle_ack(struct sock *sk, struct sk_buff *skb,
+			     struct udpcp_dest *dest)
+{
+	struct udpcphdr *r_uh;
+	struct udpcphdr *q_uh;
+
+	if (!dest->acks)
+		return;
+
+	r_uh = udpcp_hdr(skb);
+
+	/*
+	 * acks doesn't have a payload
+	 */
+	if (r_uh->length)
+		return;
+
+	q_uh = udpcp_ack_scan(dest->xmit_wait);
+
+	/*
+	 * message id, fragnum and fragamount must match the awaited message
+	 * fragment
+	 */
+	if (r_uh->msgid != q_uh->msgid)
+		return;
+
+	if (r_uh->fragnum != q_uh->fragnum)
+		return;
+
+	if (r_uh->fragamount != q_uh->fragamount)
+		return;
+
+	dest->acks--;
+
+	/*
+	 * if last fragment release message
+	 */
+	if (udpcp_is_last_frag(q_uh)) {
+		udpcp_release_xmit(sk, dest);
+
+		/*
+		 * special handling for sync messages
+		 */
+		if (r_uh->msgid == 0)
+			udpcp_sync(sk, dest);
+	} else {
+		dest->xmit_wait = dest->xmit_wait->next;
+	}
+	/*
+	 * try to transmit next message/fragment
+	 */
+	udpcp_xmit(sk, dest);
+}
+
+/*
+ * Queue incoming message as owned by udpcp socket
+ */
+static void udpcp_set_owner_r(struct sock *sk, struct udpcp_dest *dest)
+{
+	struct sk_buff *skb;
+
+	skb = dest->recv_msg;
+	skb_set_owner_r(skb, sk);
+
+	skb = skb_shinfo(skb)->frag_list;
+	if (!skb)
+		return;
+
+	for (;;) {
+		skb_set_owner_r(skb, sk);
+		if (udpcp_is_last_frag(udpcp_hdr(skb)))
+			break;
+		skb = skb->next;
+	}
+}
+
+/*
+ * Handle an incoming data message fragment
+ */
+static int udpcp_handle_data(struct sock *sk, struct sk_buff *skb,
+			     struct udpcp_dest *dest)
+{
+	struct udpcp_sock *usk = udpcp_sk(sk);
+	struct udpcphdr *uh = udpcp_hdr(skb);
+	unsigned short msginfo = ntohs(uh->msginfo);
+	unsigned short length = ntohs(uh->length);
+
+	/*
+	 * special handling for sync messages
+	 */
+	if (uh->msgid == 0) {
+		/*
+		 * sync messages doesn't have a payload
+		 */
+		if (length)
+			return 1;
+
+		/*
+		 * sync messages doesn't have a ack rules
+		 */
+		if (msginfo & (UDPCP_NO_ACK_FLAG | UDPCP_SINGLE_ACK_FLAG))
+			return 1;
+
+		udpcp_send_ack(sk, skb, dest,
+			       memcmp(uh, &dest->lastmsg,
+				      sizeof(dest->lastmsg)) ? 0 : 1);
+
+		udpcp_purge_incoming(sk, dest);
+
+		/*
+		 * skip the first message in the queue if it is a sync messages
+		 */
+		if (udpcp_xmit_is_sync(dest)) {
+			dest->acks--;
+			udpcp_dec_pending(sk);
+			kfree_skb(skb_dequeue(&dest->xmit));
+		}
+
+		if (!dest->insync)
+			udpcp_sync(sk, dest);
+
+		udpcp_xmit(sk, dest);
+
+		return -1;
+	}
+
+	if (!dest->insync)
+		return 1;
+
+	if (length > UDPCP_MAX_MSGSIZE)
+		return 1;
+
+	length += sizeof(struct udpcphdr);
+
+	/*
+	 * if the message was still handled, send a duplicate ack
+	 */
+	if (!memcmp(uh, &dest->lastmsg, sizeof(dest->lastmsg))) {
+		udpcp_send_ack(sk, skb, dest, 1);
+		return 1;
+	}
+
+	if (dest->recv_msg) {
+		/*
+		 * if a fragment is already received validate the fragment
+		 */
+		if ((uh->msgid != udpcp_hdr(dest->recv_msg)->msgid) ||
+		    (uh->msginfo != udpcp_hdr(dest->recv_msg)->msginfo) ||
+		    (uh->length != udpcp_hdr(dest->recv_msg)->length) ||
+		    (uh->fragamount != udpcp_hdr(dest->recv_msg)->fragamount)
+		    ) {
+			udpcp_purge_incoming(sk, dest);
+			goto newmsg;
+		}
+
+		if (uh->fragnum != udpcp_hdr(dest->recv_last)->fragnum + 1)
+			return 1;
+
+		if (dest->recv_msg->len + skb->len - sizeof(struct udpcphdr) >
+		    length)
+			return 1;
+	} else {
+newmsg:
+		/*
+		 * first fragment must have the number 0
+		 */
+		if (uh->fragnum != 0)
+			return 1;
+
+		/*
+		 * UDPCP data length cannot be smaller then the UDP data length
+		 */
+		if (skb->len > length)
+			return 1;
+
+		/*
+		 * id of the last received is not valid
+		 */
+		if (dest->lastmsg.msgid == uh->msgid)
+			return 1;
+
+		/*
+		 * check against receive buffer limit
+		 */
+		if (atomic_read(&sk->sk_rmem_alloc) + length > sk->sk_rcvbuf)
+			return 1;
+	}
+
+	memset(&dest->lastmsg, 0, sizeof(dest->lastmsg));
+
+	if (!dest->recv_msg) {
+		/*
+		 * store the first message fragment
+		 */
+		if (skb->cloned) {
+			struct sk_buff *skbc;
+
+			skbc = skb_copy(skb, sk->sk_allocation);
+			if (skbc == NULL)
+				return 1;
+			kfree_skb(skb);
+			skb = skbc;
+		}
+		dest->recv_msg = skb;
+	} else {
+		/*
+		 * store the consecutively message fragment
+		 */
+		struct skb_shared_info *shinfo;
+
+		shinfo = skb_shinfo(dest->recv_msg);
+
+		if (!shinfo->frag_list)
+			shinfo->frag_list = skb;
+		else
+			dest->recv_last->next = skb;
+
+		skb_pull(skb, sizeof(struct udpcphdr));
+		dest->recv_msg->len += skb->len;
+		dest->recv_msg->data_len += skb->len;
+	}
+	dest->recv_last = skb;
+
+	msginfo = ntohs(uh->msginfo);
+
+	if (udpcp_is_last_frag(uh) || uh->fragamount == 0) {
+		/*
+		 * last fragment: queue it to the socket sk_receive_queue
+		 * and ack it
+		 */
+
+		if (dest->recv_msg->len != length) {
+			udpcp_purge_incoming(sk, dest);
+			return 0;
+		}
+
+		if (!(msginfo & UDPCP_NO_ACK_FLAG))
+			udpcp_send_ack(sk, skb, dest, 0);
+
+		memcpy(dest->recv_msg->data + UDPCP_HDRSIZE,
+		       dest->recv_msg->data, sizeof(struct udphdr));
+		skb_pull(dest->recv_msg, UDPCP_HDRSIZE);
+
+		usk->stat.rx_msgs++;
+		atomic_inc(&udpcp_rx_msgs);
+
+		/*
+		 * set a flag for UDPCP message
+		 */
+		UDP_SKB_CB(skb)->udpcp_flag = 1;
+
+		udpcp_set_owner_r(sk, dest);
+		skb_queue_tail(&sk->sk_receive_queue, dest->recv_msg);
+
+		/*
+		 * call the original data available handler
+		 */
+		if (usk->udp_data_ready)
+			usk->udp_data_ready(sk, dest->recv_msg->len);
+
+		dest->recv_msg = 0;
+		dest->recv_last = 0;
+	} else {
+		/*
+		 * ack fragment if requiered
+		 */
+		if (!(msginfo & UDPCP_NO_ACK_FLAG)
+		    && !(msginfo & UDPCP_SINGLE_ACK_FLAG))
+			udpcp_send_ack(sk, skb, dest, 0);
+
+		/*
+		 * setup timeout handler
+		 */
+		dest->rx_time = jiffies;
+
+		if (!timer_pending(&usk->timer))
+			udpcp_timer(sk, dest->rx_time + usk->rx_timeout);
+	}
+
+	return 0;
+}
+
+/*
+ * Deal with received UDPCP frames - sort out what type source it is
+ * and hand of it to the udpcp_handle_packet function.
+ */
+static void udpcp_data_ready(struct sock *sk, int slen)
+{
+	struct udpcp_sock *usk = udpcp_sk(sk);
+	struct sk_buff *skb;
+	struct udpcp_dest *dest;
+	struct udpcphdr *uh;
+	unsigned short msginfo;
+	int ret;
+
+	skb = skb_peek_tail(&sk->sk_receive_queue);
+
+	/*
+	 * don't handle NULL pointer buffer and UDPCP messages
+	 */
+	if (skb == NULL || UDP_SKB_CB(skb)->udpcp_flag) {
+		if (usk->udp_data_ready)
+			usk->udp_data_ready(sk, slen);
+		return;
+	}
+
+	__skb_unlink(skb, &sk->sk_receive_queue);
+	if (udpcp_validate_skb(skb)) {
+		kfree_skb(skb);
+
+		return;
+	}
+
+	skb_orphan(skb);
+
+	/*
+	 * do UDP checksum
+	 */
+	if (udp_lib_checksum_complete(skb)) {
+		UDP_INC_STATS_BH(sock_net(sk), UDP_MIB_INERRORS, 0);
+		return;
+	}
+
+	if (unlikely(debug))
+		dump_msg("receive", skb, ip_hdr(skb)->saddr,
+			 ip_hdr(skb)->daddr);
+
+	uh = udpcp_hdr(skb);
+	msginfo = ntohs(uh->msginfo);
+
+	/*
+	 * handle only UDPCP protocol version 2
+	 */
+	if ((msginfo & UDPCP_PROTOCOL_MASK) != UDPCP_PROTOCOL_VERSION_2) {
+		kfree_skb(skb);
+		return;
+	}
+
+	/*
+	 * handle UDPCP checksum
+	 */
+	if (msginfo & UDPCP_CHECKSUM_FLAG) {
+		u8 *data;
+		u32 data_len;
+		u32 chksum;
+
+		chksum = ntohl(uh->chksum);
+		data = (u8 *) skb->data + sizeof(struct udphdr);
+		data_len = skb->len - sizeof(struct udphdr);
+
+		uh->chksum = 0;
+
+		if (chksum != zlib_adler32(1, data, data_len)) {
+			kfree_skb(skb);
+			usk->stat.crc_errors++;
+			atomic_inc(&udpcp_crc_errors);
+			return;
+		}
+	}
+
+	dest = __find_dest(sk, ip_hdr(skb)->saddr, udp_hdr(skb)->source);
+
+	if (!dest) {
+		/*
+		 * new communication destination must start with an sync message
+		 */
+		if (((msginfo & UDPCP_MSG_TYPE_MASK) != UDPCP_MSG_TYPE_DATA) ||
+		    (uh->msgid != 0)) {
+			kfree_skb(skb);
+			return;
+		}
+
+		dest = new_dest(sk, ip_hdr(skb)->saddr, udp_hdr(skb)->source);
+
+		if (!dest) {
+			kfree_skb(skb);
+			return;
+		}
+	}
+
+	/*
+	 * handle message type
+	 */
+	switch (msginfo & UDPCP_MSG_TYPE_MASK) {
+	case UDPCP_MSG_TYPE_DATA:
+		if (!(dest->use_flag & RX_NODE)) {
+			dest->use_flag |= RX_NODE;
+			usk->stat.rx_nodes++;
+			atomic_inc(&udpcp_rx_nodes);
+		}
+
+		ret = udpcp_handle_data(sk, skb, dest);
+
+		if (ret > 0) {
+			dest->rx_discarded_frags++;
+			usk->stat.rx_discarded_frags++;
+			atomic_inc(&udpcp_rx_discarded_frags);
+		}
+		break;
+	case UDPCP_MSG_TYPE_ACK:
+		udpcp_handle_ack(sk, skb, dest);
+	default:
+		ret = 1;
+		break;
+	}
+	if (ret)
+		kfree_skb(skb);
+}
+
+/*
+ * Set socket options
+ */
+static int udpcp_setsockopt(struct sock *sk, int level, int optname,
+			    char __user *optval, unsigned int optlen)
+{
+	struct udpcp_sock *usk = udpcp_sk(sk);
+	int val, ret;
+
+	if (level != SOL_UDPCP) {
+		if (udp_prot.setsockopt) {
+			ret = udp_prot.setsockopt(sk, level, optname, optval,
+						optlen);
+			check_timeout(sk);
+			return ret;
+		}
+		return -ENOPROTOOPT;
+	}
+
+	if (optlen < sizeof(int))
+		return -EINVAL;
+
+	if (get_user(val, (int __user *)optval))
+		return -EFAULT;
+
+	switch (optname) {
+	case UDPCP_OPT_TRANSFER_MODE:
+		switch (val) {
+		case UDPCP_NOACK:
+		case UDPCP_ACK:
+		case UDPCP_SINGLE_ACK:
+			usk->ackmode = val;
+			break;
+		default:
+			return -EINVAL;
+		}
+		break;
+	case UDPCP_OPT_CHECKSUM_MODE:
+		switch (val) {
+		case UDPCP_NOCHECKSUM:
+		case UDPCP_CHECKSUM:
+			usk->chkmode = val;
+			break;
+		default:
+			return -EINVAL;
+		}
+		break;
+
+	case UDPCP_OPT_TX_TIMEOUT:
+		if ((val < 1) || (val > UDPCP_MAX_WAIT_SEC * 1000))
+			return -EINVAL;
+		usk->tx_timeout = msecs_to_jiffies(val);
+		break;
+
+	case UDPCP_OPT_RX_TIMEOUT:
+		if ((val < 1) || (val > UDPCP_MAX_WAIT_SEC * 1000))
+			return -EINVAL;
+		usk->rx_timeout = msecs_to_jiffies(val);
+		break;
+
+	case UDPCP_OPT_MAXTRY:
+		if ((val < 1) || (val > 10))
+			return -EINVAL;
+		usk->maxtry = val;
+		break;
+
+	case UDPCP_OPT_OUTSTANDING_ACKS:
+		if ((val < 1) || (val > 255))
+			return -EINVAL;
+		usk->acks = val;
+		break;
+
+	default:
+		return -ENOPROTOOPT;
+	}
+	return 0;
+}
+
+/*
+ * Get socket options
+ */
+static int udpcp_getsockopt(struct sock *sk, int level, int optname,
+			    char __user *optval, int __user *optlen)
+{
+	struct udpcp_sock *usk = udpcp_sk(sk);
+	int val, len, ret;
+
+	if (level != SOL_UDPCP) {
+		if (udp_prot.getsockopt) {
+			ret = udp_prot.getsockopt(sk, level, optname, optval,
+						optlen);
+			check_timeout(sk);
+			return ret;
+		}
+		return -ENOPROTOOPT;
+	}
+
+	if (get_user(len, optlen))
+		return -EFAULT;
+
+	len = min_t(unsigned int, len, sizeof(int));
+
+	if (len < 0)
+		return -EINVAL;
+
+	switch (optname) {
+	case UDPCP_OPT_TRANSFER_MODE:
+		val = usk->ackmode;
+		break;
+
+	case UDPCP_OPT_CHECKSUM_MODE:
+		val = usk->chkmode;
+		break;
+
+	case UDPCP_OPT_TX_TIMEOUT:
+		val = jiffies_to_msecs(usk->tx_timeout);
+		break;
+
+	case UDPCP_OPT_MAXTRY:
+		val = usk->maxtry;
+		break;
+
+	case UDPCP_OPT_OUTSTANDING_ACKS:
+		val = usk->acks;
+		break;
+
+	default:
+		return -ENOPROTOOPT;
+	}
+
+	if (put_user(len, optlen))
+		return -EFAULT;
+	if (copy_to_user(optval, &val, len))
+		return -EFAULT;
+	return 0;
+}
+
+/*
+ * ioctl() requests applicable to the UDPCP protocol
+ */
+int udpcp_ioctl(struct sock *sk, int cmd, unsigned long arg)
+{
+	struct udpcp_sock *usk = udpcp_sk(sk);
+	int ret = 0;
+
+	switch (cmd) {
+	case UDPCP_IOCTL_GET_STATISTICS:
+		lock_sock(sk);
+		if (copy_to_user((void *)arg, &usk->stat, sizeof(usk->stat)))
+			ret = -EFAULT;
+		udpcp_release_sock(sk);
+		break;
+
+	case UDPCP_IOCTL_RESET_STATISTICS:
+		lock_sock(sk);
+		usk->stat.tx_msgs = 0;
+		usk->stat.rx_msgs = 0;
+		usk->stat.tx_timeout = 0;
+		usk->stat.rx_timeout = 0;
+		usk->stat.tx_retries = 0;
+		usk->stat.rx_discarded_frags = 0;
+		usk->stat.crc_errors = 0;
+		udpcp_release_sock(sk);
+		break;
+
+	case UDPCP_IOCTL_SYNC:
+		if (arg)
+			ret = wait_event_interruptible_timeout(usk->wq,
+				!usk->pending, msecs_to_jiffies(arg));
+		else
+			ret = wait_event_interruptible(usk->wq, !usk->pending);
+
+		break;
+
+	default:
+		if (udp_prot.ioctl) {
+			ret = udp_prot.ioctl(sk, cmd, arg);
+			check_timeout(sk);
+		} else {
+			ret = -ENOIOCTLCMD;
+		}
+		break;
+	}
+	return ret;
+}
+
+/*
+ * This function will be called by recv(), recvfrom() and revmsg()
+ */
+int udpcp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
+		  size_t len, int noblock, int flags, int *addr_len)
+{
+	int ret;
+
+	ret = udp_prot.recvmsg(iocb, sk, msg, len, noblock, flags, addr_len);
+	check_timeout(sk);
+	return ret;
+}
+
+/*
+ * This function will be called by socket() and initialized the socket
+ */
+static int udpcp_sockinit(struct sock *sk)
+{
+	int ret;
+	struct udpcp_sock *usk;
+
+	sk->sk_protocol = SOL_UDP;
+	sk->sk_allocation = GFP_ATOMIC;
+	if (udp_prot.init) {
+		ret = udp_prot.init(sk);
+
+		if (ret)
+			return ret;
+	}
+
+	usk = udpcp_sk(sk);
+	usk->timer.expires = 0;
+	usk->timer.function = udpcp_timeout;
+	usk->timer.data = (long)sk;
+	init_timer(&usk->timer);
+	INIT_LIST_HEAD(&usk->destlist);
+	init_waitqueue_head(&usk->wq);
+	usk->pending = 0;
+	usk->ackmode = UDPCP_ACK;
+	usk->chkmode = UDPCP_CHECKSUM;
+	usk->maxtry = UDPCP_TX_MAXTRY;
+	usk->acks = UDPCP_OUTSTANDING_ACKS;
+	usk->tx_timeout = msecs_to_jiffies(UDPCP_TX_TIMEOUT);
+	usk->rx_timeout = msecs_to_jiffies(UDPCP_RX_TIMEOUT);
+	usk->udp_data_ready = sk->sk_data_ready;
+	sk->sk_data_ready = udpcp_data_ready;
+	usk->udpsock.pending = 0;
+	skb_queue_head_init(&usk->assembly);
+	usk->assembly_len = 0;
+	usk->assembly_dest = NULL;
+
+	spin_lock_bh(&udpcp_lock);
+	list_add_tail(&usk->udpcplist, &udpcp_list);
+	spin_unlock_bh(&udpcp_lock);
+
+#ifdef MODULE
+	try_module_get(THIS_MODULE);
+#endif
+	return 0;
+}
+
+/*
+ * This function will be called by close()
+ */
+static void udpcp_destroy(struct sock *sk)
+{
+	struct list_head *p;
+	struct list_head *n;
+	struct udpcp_sock *usk = udpcp_sk(sk);
+
+	spin_lock_bh(&udpcp_lock);
+	list_del(&usk->udpcplist);
+	spin_unlock_bh(&udpcp_lock);
+
+	if (udp_prot.destroy)
+		udp_prot.destroy(sk);
+
+	lock_sock(sk);
+
+	del_timer_sync(&usk->timer);
+	sk->sk_data_ready = usk->udp_data_ready;
+
+	skb_queue_purge(&usk->assembly);
+
+	list_for_each_safe(p, n, &usk->destlist) {
+		struct udpcp_dest *dest;
+
+		dest = list_to_udpcpdest(p);
+
+		skb_queue_purge(&dest->xmit);
+
+		kfree_skb(dest->recv_msg);
+
+		if (dest->rt)
+			dst_release(&dest->rt->dst);
+
+		kfree(dest);
+	}
+
+	atomic_sub(usk->stat.tx_nodes, &udpcp_tx_nodes);
+	atomic_sub(usk->stat.rx_nodes, &udpcp_rx_nodes);
+
+	usk->pending = 0;
+
+	if (waitqueue_active(&usk->wq))
+		wake_up_interruptible(&usk->wq);
+
+	release_sock(sk);
+
+#ifdef MODULE
+	module_put(THIS_MODULE);
+#endif
+}
+
+static struct proto udpcp_prot;
+
+/*
+ * inet protocol stack descriptor
+ */
+static struct inet_protosw udpcp_protosw = {
+	.type = SOCK_DGRAM,
+	.protocol = PF_UDPCP,
+	.prot = &udpcp_prot,
+	.ops = &inet_dgram_ops,
+	.no_check = UDP_CSUM_DEFAULT,
+	.flags = 0,
+};
+
+#ifdef CONFIG_PROC_FS
+/*
+ * The following functions handles the /proc/net/udpcp entry
+ */
+struct udpcp_seq_afinfo {
+	char *name;
+	const struct file_operations seq_fops;
+	const struct seq_operations seq_ops;
+};
+
+struct udpcp_iter_state {
+	struct seq_net_private p;
+	struct sock *sk;
+	struct list_head *list;
+	int bucket;
+};
+
+static int udpcp_get_destlist(struct udpcp_sock *usk,
+			struct udpcp_iter_state *state)
+{
+	struct sock *sk = (struct sock *)usk;
+
+	if (sock_flag(sk, SOCK_DEAD))
+		return 0;
+
+	sock_hold(sk);
+	if (!list_empty(&usk->destlist)) {
+		state->sk = sk;
+		state->list = &usk->destlist;
+		return 1;
+	}
+	sock_put(sk);
+
+	return 0;
+}
+
+static inline int udpcp_next_dest(struct udpcp_iter_state *state)
+{
+	struct sock *sk = state->sk;
+	struct udpcp_sock *usk = udpcp_sk(sk);
+	int found = 0;
+
+	if (sock_flag(sk, SOCK_DEAD))
+		return 0;
+
+	lock_sock(sk);
+	if (!list_is_last(state->list, &usk->destlist)) {
+		state->list = state->list->next;
+		state->bucket++;
+		found = 1;
+	}
+	udpcp_release_sock(sk);
+	return found;
+}
+
+static void *udpcp_get_next(struct seq_file *seq)
+{
+	struct udpcp_iter_state *state = seq->private;
+	struct udpcp_sock *usk;
+	struct sock *sk;
+
+	while (state) {
+		if (udpcp_next_dest(state))
+			return state;
+
+		sk = state->sk;
+		usk = udpcp_sk(sk);
+
+		spin_lock_bh(&udpcp_lock);
+		while (!list_is_last(&usk->udpcplist, &udpcp_list)) {
+			usk = list_entry(usk->udpcplist.next, struct udpcp_sock,
+				       udpcplist);
+
+			if (udpcp_get_destlist(usk, state))
+				goto found;
+		}
+		state->sk = NULL;
+		state = NULL;
+found:
+		spin_unlock_bh(&udpcp_lock);
+		sock_put(sk);
+	}
+	return state;
+}
+
+static void *udpcp_get_first(struct seq_file *seq)
+{
+	struct list_head *p;
+	struct udpcp_iter_state *state = seq->private;
+	int found = 0;
+
+	if (!state)
+		return NULL;
+
+	spin_lock_bh(&udpcp_lock);
+	list_for_each(p, &udpcp_list) {
+		found = udpcp_get_destlist(list_to_udpcpsock(p), state);
+		if (found)
+			goto found;
+	}
+found:
+	spin_unlock_bh(&udpcp_lock);
+
+	if (!found)
+		return NULL;
+	return udpcp_get_next(seq);
+}
+
+static void *udpcp_get_idx(struct seq_file *seq, loff_t pos)
+{
+	if (!udpcp_get_first(seq))
+		return NULL;
+
+	while (pos--) {
+		if (!udpcp_get_next(seq))
+			return NULL;
+	}
+	return seq->private;
+}
+
+static void *udpcp_seq_start(struct seq_file *seq, loff_t * pos)
+{
+	return *pos ? udpcp_get_idx(seq, *pos - 1) : SEQ_START_TOKEN;
+}
+
+static void *udpcp_seq_next(struct seq_file *seq, void *v, loff_t * pos)
+{
+	void *private;
+
+	if (v == SEQ_START_TOKEN)
+		private = udpcp_get_idx(seq, 0);
+	else
+		private = udpcp_get_next(seq);
+
+	++*pos;
+	return private;
+}
+
+static void udpcp_seq_stop(struct seq_file *seq, void *v)
+{
+	struct udpcp_iter_state *state = seq->private;
+
+	if (state->sk)
+		sock_put(state->sk);
+}
+
+static int udpcp_seq_open(struct inode *inode, struct file *file)
+{
+	struct udpcp_seq_afinfo *afinfo = PDE(inode)->data;
+	int err;
+
+	err = seq_open_net(inode, file, &afinfo->seq_ops,
+			   sizeof(struct udpcp_iter_state));
+	if (err < 0)
+		return err;
+
+	return err;
+}
+
+int udpcp_proc_register(struct net *net, struct udpcp_seq_afinfo *afinfo)
+{
+	struct proc_dir_entry *p;
+	int rc = 0;
+
+	p = proc_create_data(afinfo->name, S_IRUGO, net->proc_net,
+			     &afinfo->seq_fops, afinfo);
+	if (!p)
+		rc = -ENOMEM;
+	return rc;
+}
+
+void udpcp_proc_unregister(struct net *net, struct udpcp_seq_afinfo *afinfo)
+{
+	proc_net_remove(net, afinfo->name);
+}
+
+static unsigned int udpcp_tx_queue_len(struct sock *sk, struct udpcp_dest *dest)
+{
+	struct sk_buff *skb;
+	unsigned int n = 0;
+
+	skb_queue_walk(&dest->xmit, skb)
+	    n += skb->len;
+	return n;
+}
+
+static unsigned int udpcp_rx_queue_len(struct sock *sk, struct udpcp_dest *dest)
+{
+	struct sk_buff *skb;
+	unsigned int n = 0;
+
+	skb_queue_walk(&sk->sk_receive_queue, skb) {
+		if (udp_hdr(skb)->source == dest->port
+		    && ip_hdr(skb)->saddr == dest->addr)
+			n += skb->len;
+	}
+	return n;
+}
+
+static void udpcp_format_sock(struct seq_file *seq, int *len)
+{
+	struct udpcp_iter_state *state = seq->private;
+	struct sock *sk = state->sk;
+	struct inet_sock *inet = inet_sk(sk);
+	struct udpcp_dest *p = list_to_udpcpdest(state->list);
+	__be32 src = inet->inet_rcv_saddr;
+	__u16 srcp = ntohs(inet->inet_sport);
+	__be32 dest = p->addr;
+	__u16 destp = ntohs(p->port);
+
+	lock_sock(sk);
+	seq_printf(seq, "%4d: %08X:%04X %08X:%04X"
+		   " %02X %08X:%08X %02X:%08lX %08X %5d %8d %lu %d %p %u%n",
+		   state->bucket, src, srcp, dest, destp, sk->sk_state,
+		   udpcp_tx_queue_len(sk, p),
+		   udpcp_rx_queue_len(sk, p),
+		   0, 0L, p->tx_retries, sock_i_uid(sk),
+		   p->tx_timeout, sock_i_ino(sk),
+		   atomic_read(&sk->sk_refcnt), sk, p->rx_timeout,
+		   len);
+	udpcp_release_sock(sk);
+}
+
+int udpcp_seq_show(struct seq_file *seq, void *v)
+{
+	if (v == SEQ_START_TOKEN) {
+		seq_printf(seq, "%-127s\n",
+			   "  sl  local_address rem_address   st tx_queue "
+			   "rx_queue tr tm->when retrnsmt   uid  timeout "
+			   "inode ref pointer drops");
+	} else {
+		int len;
+
+		udpcp_format_sock(seq, &len);
+		seq_printf(seq, "%*s\n", 127 - len, "");
+	}
+	return 0;
+}
+
+static struct udpcp_seq_afinfo udpcp_seq_afinfo = {
+	.name = "udpcp",
+	.seq_fops = {
+			.owner = THIS_MODULE,
+			.open = udpcp_seq_open,
+			.read = seq_read,
+			.llseek = seq_lseek,
+			.release = seq_release_net,
+		     },
+	.seq_ops = {
+			.show = udpcp_seq_show,
+			.start = udpcp_seq_start,
+			.next = udpcp_seq_next,
+			.stop = udpcp_seq_stop,
+		    },
+};
+
+static int udpcp_proc_init_net(struct net *net)
+{
+	return udpcp_proc_register(net, &udpcp_seq_afinfo);
+}
+
+static void udpcp_proc_exit_net(struct net *net)
+{
+	udpcp_proc_unregister(net, &udpcp_seq_afinfo);
+}
+
+static struct pernet_operations udpcp_net_ops = {
+	.init = udpcp_proc_init_net,
+	.exit = udpcp_proc_exit_net,
+};
+
+static int __init udpcp_proc_init(void)
+{
+	return register_pernet_subsys(&udpcp_net_ops);
+}
+
+static void udpcp_proc_exit(void)
+{
+	unregister_pernet_subsys(&udpcp_net_ops);
+}
+#endif /* CONFIG_PROC_FS */
+
+/*
+ * Install and init module
+ */
+static int __init udpcp_init(void)
+{
+	int ret;
+	struct proc_dir_entry *proc_entry = NULL;
+
+	spin_lock_init(&udpcp_lock);
+
+	INIT_LIST_HEAD(&udpcp_list);
+
+	/*
+	 * to prevent to rewrite the whole UDP protocol,
+	 * assign struct proto udp to the struct proto udpcp
+	 */
+	udpcp_prot = udp_prot;
+
+	/*
+	 * change the protocol name
+	 */
+	strcpy(udpcp_prot.name, "UDPCP");
+
+	/*
+	 * overload the following function, all other
+	 * functions will use the UDP protocol functions
+	 */
+	udpcp_prot.sendmsg = udpcp_sendmsg;
+	udpcp_prot.sendpage = udpcp_sendpage;
+	udpcp_prot.init = udpcp_sockinit;
+	udpcp_prot.destroy = udpcp_destroy;
+	udpcp_prot.setsockopt = udpcp_setsockopt;
+	udpcp_prot.getsockopt = udpcp_getsockopt;
+	udpcp_prot.ioctl = udpcp_ioctl;
+	udpcp_prot.recvmsg = udpcp_recvmsg;
+
+	/*
+	 * fix the object size for the embedded udpcp_sock structure
+	 */
+	udpcp_prot.obj_size = sizeof(struct udpcp_sock);
+
+	/*
+	 * register the UDPCP protocol
+	 */
+	ret = proto_register(&udpcp_prot, 1);
+	if (ret)
+		return ret;
+
+	/*
+	 * register the inet socket for UDPCP
+	 */
+	inet_register_protosw(&udpcp_protosw);
+
+	/*
+	 * register the /proc/sys/net/ipv4/udpcp_ entries
+	 */
+	udpcp_ctl_table =
+		register_sysctl_paths(net_ipv4_ctl_path, ipv4_udpcp_table);
+	if (udpcp_ctl_table == NULL) {
+		ret = -ENOMEM;
+		goto err1;
+	}
+
+#ifdef CONFIG_PROC_FS
+	/*
+	 * register /proc/driver/udpcp entry
+	 */
+	proc_entry =
+	    create_proc_read_entry(UDPCP_PROC, S_IRUSR | S_IRGRP | S_IROTH,
+				   NULL, udpcp_proc, NULL);
+
+	if (!proc_entry) {
+		ret = -ENOMEM;
+		goto err2;
+	}
+	/*
+	 * register /proc/net/udpcp entry
+	 */
+	ret = udpcp_proc_init();
+
+	if (ret)
+		goto err3;
+#endif
+	pr_info("UDPCP protocol stack\n");
+	return 0;
+#ifdef CONFIG_PROC_FS
+err3:
+	remove_proc_entry(UDPCP_PROC, NULL);
+err2:
+	unregister_sysctl_table(udpcp_ctl_table);
+#endif
+err1:
+	inet_unregister_protosw(&udpcp_protosw);
+	proto_unregister(&udpcp_prot);
+	return ret;
+}
+
+/*
+ * Cleanup and exit module
+ */
+static void __exit udpcp_exit(void)
+{
+#ifdef CONFIG_PROC_FS
+	udpcp_proc_exit();
+	remove_proc_entry(UDPCP_PROC, NULL);
+#endif
+	unregister_sysctl_table(udpcp_ctl_table);
+	inet_unregister_protosw(&udpcp_protosw);
+	proto_unregister(&udpcp_prot);
+}
+
+module_init(udpcp_init);
+module_exit(udpcp_exit);
+
+MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>");
+MODULE_DESCRIPTION("UDPCP protocol stack");
+MODULE_LICENSE("GPL");
+