[4/7] net/packet: Ask driver for protocol if not provided by user
diff mbox series

Message ID 20190114131841.1932-5-maximmi@mellanox.com
State Changes Requested
Delegated to: David Miller
Headers show
Series
  • AF_PACKET transport_offset fix
Related show

Commit Message

Maxim Mikityanskiy Jan. 14, 2019, 1:19 p.m. UTC
If a socket was created with socket(AF_PACKET, SOCK_RAW, 0), the
protocol number is unavailable. Try to ask the driver to extract it from
the L2 header in order for skb_try_probe_transport_header to succeed.

Signed-off-by: Maxim Mikityanskiy <maximmi@mellanox.com>
---
 net/packet/af_packet.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

Comments

Willem de Bruijn Jan. 14, 2019, 4:52 p.m. UTC | #1
On Mon, Jan 14, 2019 at 8:20 AM Maxim Mikityanskiy <maximmi@mellanox.com> wrote:
>
> If a socket was created with socket(AF_PACKET, SOCK_RAW, 0), the
> protocol number is unavailable. Try to ask the driver to extract it from
> the L2 header in order for skb_try_probe_transport_header to succeed.
>
> Signed-off-by: Maxim Mikityanskiy <maximmi@mellanox.com>
> ---
>  net/packet/af_packet.c | 15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)
>
> diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
> index 8fc76e68777a..d1d89749a17a 100644
> --- a/net/packet/af_packet.c
> +++ b/net/packet/af_packet.c
> @@ -1850,6 +1850,15 @@ static int packet_rcv_spkt(struct sk_buff *skb, struct net_device *dev,
>         return 0;
>  }
>
> +static void packet_parse_headers(struct sk_buff *skb, struct socket *sock)
> +{
> +       if (!skb->protocol && sock->type == SOCK_RAW) {
> +               skb_reset_mac_header(skb);
> +               skb->protocol = dev_parse_header_protocol(skb);
> +       }
> +
> +       skb_try_probe_transport_header(skb);
> +}


In relation to the discussion at

  af_packet: fix raw sockets over 6in4 tunnel
  http://patchwork.ozlabs.org/patch/1023623/

if adding a new header_ops callback to parse link layer headers,
please have it return both protocol and link layer header length.

also, this information may be needed earlier in (t)packet_snd than the
transport header, so I would suggest not combining the two in a new
packet_parse_headers wrapper function.
Willem de Bruijn Jan. 15, 2019, 4:32 p.m. UTC | #2
On Mon, Jan 14, 2019 at 11:52 AM Willem de Bruijn
<willemdebruijn.kernel@gmail.com> wrote:
>
> On Mon, Jan 14, 2019 at 8:20 AM Maxim Mikityanskiy <maximmi@mellanox.com> wrote:
> >
> > If a socket was created with socket(AF_PACKET, SOCK_RAW, 0), the
> > protocol number is unavailable. Try to ask the driver to extract it from
> > the L2 header in order for skb_try_probe_transport_header to succeed.
> >
> > Signed-off-by: Maxim Mikityanskiy <maximmi@mellanox.com>
> > ---
> >  net/packet/af_packet.c | 15 ++++++++++++---
> >  1 file changed, 12 insertions(+), 3 deletions(-)
> >
> > diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
> > index 8fc76e68777a..d1d89749a17a 100644
> > --- a/net/packet/af_packet.c
> > +++ b/net/packet/af_packet.c
> > @@ -1850,6 +1850,15 @@ static int packet_rcv_spkt(struct sk_buff *skb, struct net_device *dev,
> >         return 0;
> >  }
> >
> > +static void packet_parse_headers(struct sk_buff *skb, struct socket *sock)
> > +{
> > +       if (!skb->protocol && sock->type == SOCK_RAW) {
> > +               skb_reset_mac_header(skb);
> > +               skb->protocol = dev_parse_header_protocol(skb);
> > +       }
> > +
> > +       skb_try_probe_transport_header(skb);
> > +}
>
>
> In relation to the discussion at
>
>   af_packet: fix raw sockets over 6in4 tunnel
>   http://patchwork.ozlabs.org/patch/1023623/
>
> if adding a new header_ops callback to parse link layer headers,
> please have it return both protocol and link layer header length.

This could just be an extension of existing header_ops->validate.
Maxim Mikityanskiy Jan. 17, 2019, 9:10 a.m. UTC | #3
> > > +static void packet_parse_headers(struct sk_buff *skb, struct socket
> *sock)
> > > +{
> > > +       if (!skb->protocol && sock->type == SOCK_RAW) {
> > > +               skb_reset_mac_header(skb);
> > > +               skb->protocol = dev_parse_header_protocol(skb);
> > > +       }
> > > +
> > > +       skb_try_probe_transport_header(skb);
> > > +}
> >
> >
> > In relation to the discussion at
> >
> >   af_packet: fix raw sockets over 6in4 tunnel
> >   http://patchwork.ozlabs.org/patch/1023623/
> >
> > if adding a new header_ops callback to parse link layer headers,
> > please have it return both protocol and link layer header length.

Sorry, I miss the point here, can you elaborate more? If all you need is
to have some header_ops callback that returns the L2 header length,
there is one already, it's called parse. Or do you have a specific
reason why you want my callback to also return the header length?

> This could just be an extension of existing header_ops->validate.

If you suggest extending an existing function, parse looks more
suitable, but I decided not to touch the existing ones for two reasons:

1. I don't want to break the existing code that uses the parse function
and will need to be modified to pass an extra parameter.

2. I don't want to spend machine time on copying the destination MAC
when I only need the protocol, and vice versa.

I'm looking forward to hearing your thoughts about it.
Willem de Bruijn Jan. 17, 2019, 3:41 p.m. UTC | #4
On Thu, Jan 17, 2019 at 4:10 AM Maxim Mikityanskiy <maximmi@mellanox.com> wrote:
>
> > > > +static void packet_parse_headers(struct sk_buff *skb, struct socket
> > *sock)
> > > > +{
> > > > +       if (!skb->protocol && sock->type == SOCK_RAW) {
> > > > +               skb_reset_mac_header(skb);
> > > > +               skb->protocol = dev_parse_header_protocol(skb);
> > > > +       }
> > > > +
> > > > +       skb_try_probe_transport_header(skb);
> > > > +}
> > >
> > >
> > > In relation to the discussion at
> > >
> > >   af_packet: fix raw sockets over 6in4 tunnel
> > >   http://patchwork.ozlabs.org/patch/1023623/
> > >
> > > if adding a new header_ops callback to parse link layer headers,
> > > please have it return both protocol and link layer header length.
>
> Sorry, I miss the point here, can you elaborate more? If all you need is
> to have some header_ops callback that returns the L2 header length,
> there is one already, it's called parse. Or do you have a specific
> reason why you want my callback to also return the header length?

The main reason is to avoid multiple indirect function calls, both
essentially doing the same: parsing the ll header. But admittedly the
instances where dev->header_ops->validate are called are rare.

> > This could just be an extension of existing header_ops->validate.
>
> If you suggest extending an existing function, parse looks more
> suitable, but I decided not to touch the existing ones for two reasons:
>
> 1. I don't want to break the existing code that uses the parse function
> and will need to be modified to pass an extra parameter.
>
> 2. I don't want to spend machine time on copying the destination MAC
> when I only need the protocol, and vice versa.
>
> I'm looking forward to hearing your thoughts about it.

header_ops.parse is also a good candidate. As a matter of fact, parse
and validate could (eventually) probably be combined.

The only direct caller to header_ops.parse appears to be
dev_parse_header, so modifying its interface should be fairly
straightforward. Allowing a NULL haddr could avoid the address copy
cost if not needed. This does require modifying all implementations.
But from a quick scan, there appear to be only 8. And only 1 for
validate. So changing the implementation is quite acceptable. Another
issue, though, would be what to return as protocol if a header does
not encode that.

Given these non-trivial changes, if you prefer to just add the
dedicated new callback, that's fine. We can see independently whether
deduplication makes sense. With three ll header parse functions, I
think that it will be. But even if so, it is better to do so as a
stand-alone noop patch than combining refactoring and new features,
anyway.

Long story short, sounds good. Thanks.

Patch
diff mbox series

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 8fc76e68777a..d1d89749a17a 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1850,6 +1850,15 @@  static int packet_rcv_spkt(struct sk_buff *skb, struct net_device *dev,
 	return 0;
 }
 
+static void packet_parse_headers(struct sk_buff *skb, struct socket *sock)
+{
+	if (!skb->protocol && sock->type == SOCK_RAW) {
+		skb_reset_mac_header(skb);
+		skb->protocol = dev_parse_header_protocol(skb);
+	}
+
+	skb_try_probe_transport_header(skb);
+}
 
 /*
  *	Output a raw packet to a device layer. This bypasses all the other
@@ -1970,7 +1979,7 @@  static int packet_sendmsg_spkt(struct socket *sock, struct msghdr *msg,
 	if (unlikely(extra_len == 4))
 		skb->no_fcs = 1;
 
-	skb_try_probe_transport_header(skb);
+	packet_parse_headers(skb, sock);
 
 	dev_queue_xmit(skb);
 	rcu_read_unlock();
@@ -2519,7 +2528,7 @@  static int tpacket_fill_skb(struct packet_sock *po, struct sk_buff *skb,
 		len = ((to_write > len_max) ? len_max : to_write);
 	}
 
-	skb_try_probe_transport_header(skb);
+	packet_parse_headers(skb, sock);
 
 	return tp_len;
 }
@@ -2924,7 +2933,7 @@  static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len)
 		virtio_net_hdr_set_proto(skb, &vnet_hdr);
 	}
 
-	skb_try_probe_transport_header(skb);
+	packet_parse_headers(skb, sock);
 
 	if (unlikely(extra_len == 4))
 		skb->no_fcs = 1;