diff mbox

[PATCHv7,4/9] slirp: Factorizing tcpiphdr structure with an union

Message ID e9b57bb9d1b749fe7858d42bce620e64e1046fa3.1455471945.git.samuel.thibault@ens-lyon.org
State New
Headers show

Commit Message

Samuel Thibault Feb. 14, 2016, 5:47 p.m. UTC 
From: Guillaume Subiron <maethor@subiron.org>

This patch factorizes the tcpiphdr structure to put the IPv4 fields in
an union, for addition of version 6 in further patch.
Using some macros, retrocompatibility of the existing code is assured.

This patch also fixes the SLIRP_MSIZE and margin computation in various
functions, and makes them compatible with the new tcpiphdr structure,
whose size will be bigger than sizeof(struct tcphdr) + sizeof(struct ip)

Signed-off-by: Guillaume Subiron <maethor@subiron.org>
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
---
 slirp/if.h         |  4 ++--
 slirp/mbuf.c       |  3 ++-
 slirp/slirp.c      | 15 ++++++++-------
 slirp/socket.c     | 13 ++++++++++++-
 slirp/tcp_input.c  | 31 ++++++++++++++++++++-----------
 slirp/tcp_output.c | 18 +++++++++++++-----
 slirp/tcp_subr.c   | 31 ++++++++++++++++++++++---------
 slirp/tcpip.h      | 31 +++++++++++++++++++++++--------
 8 files changed, 102 insertions(+), 44 deletions(-)

Comments

Samuel Thibault Feb. 19, 2016, 12:36 a.m. UTC | #1 
Hello,

Just to make sure: we have not received comments on this patch.

(that said, it's the most complex part of the series, so I'm not
surprised if it takes more time :) )

Samuel

Samuel Thibault, on Sun 14 Feb 2016 18:47:38 +0100, wrote:
> From: Guillaume Subiron <maethor@subiron.org>
> 
> This patch factorizes the tcpiphdr structure to put the IPv4 fields in
> an union, for addition of version 6 in further patch.
> Using some macros, retrocompatibility of the existing code is assured.
> 
> This patch also fixes the SLIRP_MSIZE and margin computation in various
> functions, and makes them compatible with the new tcpiphdr structure,
> whose size will be bigger than sizeof(struct tcphdr) + sizeof(struct ip)
> 
> Signed-off-by: Guillaume Subiron <maethor@subiron.org>
> Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
> ---
>  slirp/if.h         |  4 ++--
>  slirp/mbuf.c       |  3 ++-
>  slirp/slirp.c      | 15 ++++++++-------
>  slirp/socket.c     | 13 ++++++++++++-
>  slirp/tcp_input.c  | 31 ++++++++++++++++++++-----------
>  slirp/tcp_output.c | 18 +++++++++++++-----
>  slirp/tcp_subr.c   | 31 ++++++++++++++++++++++---------
>  slirp/tcpip.h      | 31 +++++++++++++++++++++++--------
>  8 files changed, 102 insertions(+), 44 deletions(-)
> 
> diff --git a/slirp/if.h b/slirp/if.h
> index 3327023..c7a5c57 100644
> --- a/slirp/if.h
> +++ b/slirp/if.h
> @@ -17,7 +17,7 @@
>  #define IF_MRU 1500
>  #define	IF_COMP IF_AUTOCOMP	/* Flags for compression */
>  
> -/* 2 for alignment, 14 for ethernet, 40 for TCP/IP */
> -#define IF_MAXLINKHDR (2 + 14 + 40)
> +/* 2 for alignment, 14 for ethernet */
> +#define IF_MAXLINKHDR (2 + ETH_HLEN)
>  
>  #endif
> diff --git a/slirp/mbuf.c b/slirp/mbuf.c
> index c959758..f081c69 100644
> --- a/slirp/mbuf.c
> +++ b/slirp/mbuf.c
> @@ -24,7 +24,8 @@
>   * Find a nice value for msize
>   * XXX if_maxlinkhdr already in mtu
>   */
> -#define SLIRP_MSIZE (IF_MTU + IF_MAXLINKHDR + offsetof(struct mbuf, m_dat) + 6)
> +#define SLIRP_MSIZE\
> +    (offsetof(struct mbuf, m_dat) + IF_MAXLINKHDR + TCPIPHDR_DELTA + IF_MTU)
>  
>  void
>  m_init(Slirp *slirp)
> diff --git a/slirp/slirp.c b/slirp/slirp.c
> index 5f42ada..c2c4597 100644
> --- a/slirp/slirp.c
> +++ b/slirp/slirp.c
> @@ -754,15 +754,16 @@ void slirp_input(Slirp *slirp, const uint8_t *pkt, int pkt_len)
>          m = m_get(slirp);
>          if (!m)
>              return;
> -        /* Note: we add to align the IP header */
> -        if (M_FREEROOM(m) < pkt_len + 2) {
> -            m_inc(m, pkt_len + 2);
> +        /* Note: we add 2 to align the IP header on 4 bytes,
> +         * and add the margin for the tcpiphdr overhead  */
> +        if (M_FREEROOM(m) < pkt_len + TCPIPHDR_DELTA + 2) {
> +            m_inc(m, pkt_len + TCPIPHDR_DELTA + 2);
>          }
> -        m->m_len = pkt_len + 2;
> -        memcpy(m->m_data + 2, pkt, pkt_len);
> +        m->m_len = pkt_len + TCPIPHDR_DELTA + 2;
> +        memcpy(m->m_data + TCPIPHDR_DELTA + 2, pkt, pkt_len);
>  
> -        m->m_data += 2 + ETH_HLEN;
> -        m->m_len -= 2 + ETH_HLEN;
> +        m->m_data += TCPIPHDR_DELTA + 2 + ETH_HLEN;
> +        m->m_len -= TCPIPHDR_DELTA + 2 + ETH_HLEN;
>  
>          if (proto == ETH_P_IP) {
>              ip_input(m);
> diff --git a/slirp/socket.c b/slirp/socket.c
> index b79ddec..d4b02c8 100644
> --- a/slirp/socket.c
> +++ b/slirp/socket.c
> @@ -483,7 +483,18 @@ sorecvfrom(struct socket *so)
>  	  if (!m) {
>  	      return;
>  	  }
> -	  m->m_data += IF_MAXLINKHDR;
> +	  switch (so->so_ffamily) {
> +	  case AF_INET:
> +	      m->m_data += IF_MAXLINKHDR + sizeof(struct udpiphdr);
> +	      break;
> +	  case AF_INET6:
> +	      m->m_data += IF_MAXLINKHDR + sizeof(struct ip6)
> +	                                 + sizeof(struct udphdr);
> +	      break;
> +	  default:
> +	      g_assert_not_reached();
> +	      break;
> +	  }
>  
>  	  /*
>  	   * XXX Shouldn't FIONREAD packets destined for port 53,
> diff --git a/slirp/tcp_input.c b/slirp/tcp_input.c
> index 5f845da..26b0c8b 100644
> --- a/slirp/tcp_input.c
> +++ b/slirp/tcp_input.c
> @@ -256,11 +256,6 @@ tcp_input(struct mbuf *m, int iphlen, struct socket *inso)
>  	}
>  	slirp = m->slirp;
>  
> -	/*
> -	 * Get IP and TCP header together in first mbuf.
> -	 * Note: IP leaves IP header in first mbuf.
> -	 */
> -	ti = mtod(m, struct tcpiphdr *);
>  	if (iphlen > sizeof(struct ip )) {
>  	  ip_stripoptions(m, (struct mbuf *)0);
>  	  iphlen=sizeof(struct ip );
> @@ -277,14 +272,28 @@ tcp_input(struct mbuf *m, int iphlen, struct socket *inso)
>  	save_ip.ip_len+= iphlen;
>  
>  	/*
> +	 * Get IP and TCP header together in first mbuf.
> +	 * Note: IP leaves IP header in first mbuf.
> +	 */
> +	m->m_data -= sizeof(struct tcpiphdr) - (sizeof(struct ip)
> +	                                     + sizeof(struct tcphdr));
> +	m->m_len += sizeof(struct tcpiphdr) - (sizeof(struct ip)
> +	                                    + sizeof(struct tcphdr));
> +	ti = mtod(m, struct tcpiphdr *);
> +
> +	/*
>  	 * Checksum extended TCP header and data.
>  	 */
> -	tlen = ((struct ip *)ti)->ip_len;
> -        tcpiphdr2qlink(ti)->next = tcpiphdr2qlink(ti)->prev = NULL;
> -        memset(&ti->ti_i.ih_mbuf, 0 , sizeof(struct mbuf_ptr));
> -	ti->ti_x1 = 0;
> +	tlen = ip->ip_len;
> +	tcpiphdr2qlink(ti)->next = tcpiphdr2qlink(ti)->prev = NULL;
> +	memset(&ti->ih_mbuf, 0 , sizeof(struct mbuf_ptr));
> +	memset(&ti->ti, 0, sizeof(ti->ti));
> +	ti->ti_x0 = 0;
> +	ti->ti_src = save_ip.ip_src;
> +	ti->ti_dst = save_ip.ip_dst;
> +	ti->ti_pr = save_ip.ip_p;
>  	ti->ti_len = htons((uint16_t)tlen);
> -	len = sizeof(struct ip ) + tlen;
> +	len = ((sizeof(struct tcpiphdr) - sizeof(struct tcphdr)) + tlen);
>  	if(cksum(m, len)) {
>  	  goto drop;
>  	}
> @@ -1475,7 +1484,7 @@ tcp_mss(struct tcpcb *tp, u_int offer)
>  	DEBUG_ARG("tp = %p", tp);
>  	DEBUG_ARG("offer = %d", offer);
>  
> -	mss = min(IF_MTU, IF_MRU) - sizeof(struct tcpiphdr);
> +	mss = min(IF_MTU, IF_MRU) - sizeof(struct tcphdr) + sizeof(struct ip);
>  	if (offer)
>  		mss = min(mss, offer);
>  	mss = max(mss, 32);
> diff --git a/slirp/tcp_output.c b/slirp/tcp_output.c
> index 34e4d2e..7fc6a87 100644
> --- a/slirp/tcp_output.c
> +++ b/slirp/tcp_output.c
> @@ -448,15 +448,23 @@ send:
>  	 */
>  	m->m_len = hdrlen + len; /* XXX Needed? m_len should be correct */
>  
> -    {
> +	struct tcpiphdr tcpiph_save = *(mtod(m, struct tcpiphdr *));
> +	m->m_data += sizeof(struct tcpiphdr) - sizeof(struct tcphdr)
> +	                                     - sizeof(struct ip);
> +	m->m_len  -= sizeof(struct tcpiphdr) - sizeof(struct tcphdr)
> +	                                     - sizeof(struct ip);
> +	struct ip *ip = mtod(m, struct ip *);
>  
> -	((struct ip *)ti)->ip_len = m->m_len;
> +	ip->ip_len = m->m_len;
> +	ip->ip_dst = tcpiph_save.ti_dst;
> +	ip->ip_src = tcpiph_save.ti_src;
> +	ip->ip_p = tcpiph_save.ti_pr;
>  
> -	((struct ip *)ti)->ip_ttl = IPDEFTTL;
> -	((struct ip *)ti)->ip_tos = so->so_iptos;
> +	ip->ip_ttl = IPDEFTTL;
> +	ip->ip_tos = so->so_iptos;
>  
>  	error = ip_output(so, m);
> -    }
> +
>  	if (error) {
>  out:
>  		return (error);
> diff --git a/slirp/tcp_subr.c b/slirp/tcp_subr.c
> index b1aa1f2..cd021df 100644
> --- a/slirp/tcp_subr.c
> +++ b/slirp/tcp_subr.c
> @@ -76,9 +76,10 @@ tcp_template(struct tcpcb *tp)
>  	register struct tcpiphdr *n = &tp->t_template;
>  
>  	n->ti_mbuf = NULL;
> -	n->ti_x1 = 0;
> +	memset(&n->ti, 0, sizeof(n->ti));
> +	n->ti_x0 = 0;
>  	n->ti_pr = IPPROTO_TCP;
> -	n->ti_len = htons(sizeof (struct tcpiphdr) - sizeof (struct ip));
> +	n->ti_len = htons(sizeof(struct tcphdr));
>  	n->ti_src = so->so_faddr;
>  	n->ti_dst = so->so_laddr;
>  	n->ti_sport = so->so_fport;
> @@ -131,6 +132,7 @@ tcp_respond(struct tcpcb *tp, struct tcpiphdr *ti, struct mbuf *m,
>  		m->m_data += IF_MAXLINKHDR;
>  		*mtod(m, struct tcpiphdr *) = *ti;
>  		ti = mtod(m, struct tcpiphdr *);
> +		memset(&ti->ti, 0, sizeof(ti->ti));
>  		flags = TH_ACK;
>  	} else {
>  		/*
> @@ -150,8 +152,8 @@ tcp_respond(struct tcpcb *tp, struct tcpiphdr *ti, struct mbuf *m,
>  	tlen += sizeof (struct tcpiphdr);
>  	m->m_len = tlen;
>  
> -        ti->ti_mbuf = NULL;
> -	ti->ti_x1 = 0;
> +	ti->ti_mbuf = NULL;
> +	ti->ti_x0 = 0;
>  	ti->ti_seq = htonl(seq);
>  	ti->ti_ack = htonl(ack);
>  	ti->ti_x2 = 0;
> @@ -164,12 +166,23 @@ tcp_respond(struct tcpcb *tp, struct tcpiphdr *ti, struct mbuf *m,
>  	ti->ti_urp = 0;
>  	ti->ti_sum = 0;
>  	ti->ti_sum = cksum(m, tlen);
> -	((struct ip *)ti)->ip_len = tlen;
>  
> -	if(flags & TH_RST)
> -	  ((struct ip *)ti)->ip_ttl = MAXTTL;
> -	else
> -	  ((struct ip *)ti)->ip_ttl = IPDEFTTL;
> +	struct tcpiphdr tcpiph_save = *(mtod(m, struct tcpiphdr *));
> +	m->m_data += sizeof(struct tcpiphdr) - sizeof(struct tcphdr)
> +	                                     - sizeof(struct ip);
> +	m->m_len  -= sizeof(struct tcpiphdr) - sizeof(struct tcphdr)
> +	                                     - sizeof(struct ip);
> +	struct ip *ip = mtod(m, struct ip *);
> +	ip->ip_len = tlen;
> +	ip->ip_dst = tcpiph_save.ti_dst;
> +	ip->ip_src = tcpiph_save.ti_src;
> +	ip->ip_p = tcpiph_save.ti_pr;
> +
> +	if (flags & TH_RST) {
> +		ip->ip_ttl = MAXTTL;
> +	} else {
> +		ip->ip_ttl = IPDEFTTL;
> +	}
>  
>  	(void) ip_output((struct socket *)0, m);
>  }
> diff --git a/slirp/tcpip.h b/slirp/tcpip.h
> index 7974ce3..3c5d127 100644
> --- a/slirp/tcpip.h
> +++ b/slirp/tcpip.h
> @@ -37,15 +37,23 @@
>   * Tcp+ip header, after ip options removed.
>   */
>  struct tcpiphdr {
> -	struct 	ipovly ti_i;		/* overlaid ip structure */
> -	struct	tcphdr ti_t;		/* tcp header */
> +    struct mbuf_ptr ih_mbuf;	/* backpointer to mbuf */
> +    union {
> +        struct {
> +            struct  in_addr ih_src; /* source internet address */
> +            struct  in_addr ih_dst; /* destination internet address */
> +            uint8_t ih_x1;          /* (unused) */
> +            uint8_t ih_pr;          /* protocol */
> +        } ti_i4;
> +    } ti;
> +    uint16_t    ti_x0;
> +    uint16_t    ti_len;             /* protocol length */
> +    struct      tcphdr ti_t;        /* tcp header */
>  };
> -#define	ti_mbuf		ti_i.ih_mbuf.mptr
> -#define	ti_x1		ti_i.ih_x1
> -#define	ti_pr		ti_i.ih_pr
> -#define	ti_len		ti_i.ih_len
> -#define	ti_src		ti_i.ih_src
> -#define	ti_dst		ti_i.ih_dst
> +#define	ti_mbuf		ih_mbuf.mptr
> +#define	ti_pr		ti.ti_i4.ih_pr
> +#define	ti_src		ti.ti_i4.ih_src
> +#define	ti_dst		ti.ti_i4.ih_dst
>  #define	ti_sport	ti_t.th_sport
>  #define	ti_dport	ti_t.th_dport
>  #define	ti_seq		ti_t.th_seq
> @@ -65,6 +73,13 @@ struct tcpiphdr {
>  #define tcpfrag_list_end(F, T) (tcpiphdr2qlink(F) == (struct qlink*)(T))
>  #define tcpfrag_list_empty(T) ((T)->seg_next == (struct tcpiphdr*)(T))
>  
> +/* This is the difference between the size of a tcpiphdr structure, and the
> + * size of actual ip+tcp headers, rounded up since we need to align data.  */
> +#define TCPIPHDR_DELTA\
> +    (max(0,\
> +         (sizeof(struct tcpiphdr)\
> +          - sizeof(struct ip) - sizeof(struct tcphdr) + 3) & ~3))
> +
>  /*
>   * Just a clean way to get to the first byte
>   * of the packet
> -- 
> 2.7.0
> 
>
Thomas Huth Feb. 19, 2016, 1:44 p.m. UTC | #2 
On 14.02.2016 18:47, Samuel Thibault wrote:
> From: Guillaume Subiron <maethor@subiron.org>
> 
> This patch factorizes the tcpiphdr structure to put the IPv4 fields in
> an union, for addition of version 6 in further patch.
> Using some macros, retrocompatibility of the existing code is assured.
> 
> This patch also fixes the SLIRP_MSIZE and margin computation in various
> functions, and makes them compatible with the new tcpiphdr structure,
> whose size will be bigger than sizeof(struct tcphdr) + sizeof(struct ip)
> 
> Signed-off-by: Guillaume Subiron <maethor@subiron.org>
> Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
> ---
>  slirp/if.h         |  4 ++--
>  slirp/mbuf.c       |  3 ++-
>  slirp/slirp.c      | 15 ++++++++-------
>  slirp/socket.c     | 13 ++++++++++++-
>  slirp/tcp_input.c  | 31 ++++++++++++++++++++-----------
>  slirp/tcp_output.c | 18 +++++++++++++-----
>  slirp/tcp_subr.c   | 31 ++++++++++++++++++++++---------
>  slirp/tcpip.h      | 31 +++++++++++++++++++++++--------
>  8 files changed, 102 insertions(+), 44 deletions(-)
> 
> diff --git a/slirp/if.h b/slirp/if.h
> index 3327023..c7a5c57 100644
> --- a/slirp/if.h
> +++ b/slirp/if.h
> @@ -17,7 +17,7 @@
>  #define IF_MRU 1500
>  #define	IF_COMP IF_AUTOCOMP	/* Flags for compression */
>  
> -/* 2 for alignment, 14 for ethernet, 40 for TCP/IP */
> -#define IF_MAXLINKHDR (2 + 14 + 40)
> +/* 2 for alignment, 14 for ethernet */
> +#define IF_MAXLINKHDR (2 + ETH_HLEN)
>  
>  #endif
> diff --git a/slirp/mbuf.c b/slirp/mbuf.c
> index c959758..f081c69 100644
> --- a/slirp/mbuf.c
> +++ b/slirp/mbuf.c
> @@ -24,7 +24,8 @@
>   * Find a nice value for msize
>   * XXX if_maxlinkhdr already in mtu

Maybe you should now remove the XXX line, now that the size of the
TCP/IP headers is counted via IF_MTU instead?

>   */
> -#define SLIRP_MSIZE (IF_MTU + IF_MAXLINKHDR + offsetof(struct mbuf, m_dat) + 6)
> +#define SLIRP_MSIZE\
> +    (offsetof(struct mbuf, m_dat) + IF_MAXLINKHDR + TCPIPHDR_DELTA + IF_MTU)
>  
>  void
>  m_init(Slirp *slirp)
...
> diff --git a/slirp/tcp_input.c b/slirp/tcp_input.c
> index 5f845da..26b0c8b 100644
> --- a/slirp/tcp_input.c
> +++ b/slirp/tcp_input.c
> @@ -256,11 +256,6 @@ tcp_input(struct mbuf *m, int iphlen, struct socket *inso)
>  	}
>  	slirp = m->slirp;
>  
> -	/*
> -	 * Get IP and TCP header together in first mbuf.
> -	 * Note: IP leaves IP header in first mbuf.
> -	 */
> -	ti = mtod(m, struct tcpiphdr *);
>  	if (iphlen > sizeof(struct ip )) {
>  	  ip_stripoptions(m, (struct mbuf *)0);
>  	  iphlen=sizeof(struct ip );
> @@ -277,14 +272,28 @@ tcp_input(struct mbuf *m, int iphlen, struct socket *inso)
>  	save_ip.ip_len+= iphlen;
>  
>  	/*
> +	 * Get IP and TCP header together in first mbuf.
> +	 * Note: IP leaves IP header in first mbuf.
> +	 */
> +	m->m_data -= sizeof(struct tcpiphdr) - (sizeof(struct ip)
> +	                                     + sizeof(struct tcphdr));
> +	m->m_len += sizeof(struct tcpiphdr) - (sizeof(struct ip)
> +	                                    + sizeof(struct tcphdr));

I'm somewhat having a hard time to understand the  "+ sizeof(struct
tcphdr))" here.

In the tcp_output.c code, there is this:

	m->m_data += sizeof(struct tcpiphdr) - sizeof(struct tcphdr)
	                                     - sizeof(struct ip);

So with my limited point of view, I'd rather expect this here in
tcp_input.c:

	m->m_data -= sizeof(struct tcpiphdr) - (sizeof(struct ip)
	                                     - sizeof(struct tcphdr));
i.e. "-" instead of "+" here ----------------^

Could you maybe elaborate a little bit on the above calculation? Or is
it just a bug?

> +	ti = mtod(m, struct tcpiphdr *);
> +
> +	/*
>  	 * Checksum extended TCP header and data.
>  	 */
> -	tlen = ((struct ip *)ti)->ip_len;
> -        tcpiphdr2qlink(ti)->next = tcpiphdr2qlink(ti)->prev = NULL;
> -        memset(&ti->ti_i.ih_mbuf, 0 , sizeof(struct mbuf_ptr));
> -	ti->ti_x1 = 0;
> +	tlen = ip->ip_len;
> +	tcpiphdr2qlink(ti)->next = tcpiphdr2qlink(ti)->prev = NULL;
> +	memset(&ti->ih_mbuf, 0 , sizeof(struct mbuf_ptr));
> +	memset(&ti->ti, 0, sizeof(ti->ti));
> +	ti->ti_x0 = 0;
> +	ti->ti_src = save_ip.ip_src;
> +	ti->ti_dst = save_ip.ip_dst;
> +	ti->ti_pr = save_ip.ip_p;
>  	ti->ti_len = htons((uint16_t)tlen);
> -	len = sizeof(struct ip ) + tlen;
> +	len = ((sizeof(struct tcpiphdr) - sizeof(struct tcphdr)) + tlen);
>  	if(cksum(m, len)) {
>  	  goto drop;
>  	}
> @@ -1475,7 +1484,7 @@ tcp_mss(struct tcpcb *tp, u_int offer)
>  	DEBUG_ARG("tp = %p", tp);
>  	DEBUG_ARG("offer = %d", offer);
>  
> -	mss = min(IF_MTU, IF_MRU) - sizeof(struct tcpiphdr);
> +	mss = min(IF_MTU, IF_MRU) - sizeof(struct tcphdr) + sizeof(struct ip);
>  	if (offer)
>  		mss = min(mss, offer);
>  	mss = max(mss, 32);
> diff --git a/slirp/tcp_output.c b/slirp/tcp_output.c
> index 34e4d2e..7fc6a87 100644
> --- a/slirp/tcp_output.c
> +++ b/slirp/tcp_output.c
> @@ -448,15 +448,23 @@ send:
>  	 */
>  	m->m_len = hdrlen + len; /* XXX Needed? m_len should be correct */
>  
> -    {
> +	struct tcpiphdr tcpiph_save = *(mtod(m, struct tcpiphdr *));
> +	m->m_data += sizeof(struct tcpiphdr) - sizeof(struct tcphdr)
> +	                                     - sizeof(struct ip);
> +	m->m_len  -= sizeof(struct tcpiphdr) - sizeof(struct tcphdr)
> +	                                     - sizeof(struct ip);
> +	struct ip *ip = mtod(m, struct ip *);
>  
> -	((struct ip *)ti)->ip_len = m->m_len;
> +	ip->ip_len = m->m_len;
> +	ip->ip_dst = tcpiph_save.ti_dst;
> +	ip->ip_src = tcpiph_save.ti_src;
> +	ip->ip_p = tcpiph_save.ti_pr;
>  
> -	((struct ip *)ti)->ip_ttl = IPDEFTTL;
> -	((struct ip *)ti)->ip_tos = so->so_iptos;
> +	ip->ip_ttl = IPDEFTTL;
> +	ip->ip_tos = so->so_iptos;
>  
>  	error = ip_output(so, m);
> -    }
> +
>  	if (error) {
>  out:
>  		return (error);

 Thomas
Samuel Thibault Feb. 22, 2016, 1:48 a.m. UTC | #3 
Hello,

Thomas Huth, on Fri 19 Feb 2016 14:44:59 +0100, wrote:
> > +	m->m_data -= sizeof(struct tcpiphdr) - (sizeof(struct ip)
> > +	                                     + sizeof(struct tcphdr));
> > +	m->m_len += sizeof(struct tcpiphdr) - (sizeof(struct ip)
> > +	                                    + sizeof(struct tcphdr));
> 
> I'm somewhat having a hard time to understand the  "+ sizeof(struct
> tcphdr))" here.
> 
> In the tcp_output.c code, there is this:
> 
> 	m->m_data += sizeof(struct tcpiphdr) - sizeof(struct tcphdr)
> 	                                     - sizeof(struct ip);
> 
> So with my limited point of view, I'd rather expect this here in
> tcp_input.c:
> 
> 	m->m_data -= sizeof(struct tcpiphdr) - (sizeof(struct ip)
> 	                                     - sizeof(struct tcphdr));
> i.e. "-" instead of "+" here ----------------^

The parentheses and indentation were misleading actually, here is how it
should actually looks like:

> > +	m->m_data -= sizeof(struct tcpiphdr) - ( sizeof(struct ip)
> > +	                                         + sizeof(struct tcphdr));

I've now dropped the parentheses, so it looks like the tcp_output.c code:

	m->m_data -= sizeof(struct tcpiphdr) - sizeof(struct ip)
	                                     - sizeof(struct tcphdr);

Samuel
Thomas Huth Feb. 22, 2016, 7:56 a.m. UTC | #4 
On 22.02.2016 02:48, Samuel Thibault wrote:
> Hello,
> 
> Thomas Huth, on Fri 19 Feb 2016 14:44:59 +0100, wrote:
>>> +	m->m_data -= sizeof(struct tcpiphdr) - (sizeof(struct ip)
>>> +	                                     + sizeof(struct tcphdr));
>>> +	m->m_len += sizeof(struct tcpiphdr) - (sizeof(struct ip)
>>> +	                                    + sizeof(struct tcphdr));
>>
>> I'm somewhat having a hard time to understand the  "+ sizeof(struct
>> tcphdr))" here.
>>
>> In the tcp_output.c code, there is this:
>>
>> 	m->m_data += sizeof(struct tcpiphdr) - sizeof(struct tcphdr)
>> 	                                     - sizeof(struct ip);
>>
>> So with my limited point of view, I'd rather expect this here in
>> tcp_input.c:
>>
>> 	m->m_data -= sizeof(struct tcpiphdr) - (sizeof(struct ip)
>> 	                                     - sizeof(struct tcphdr));
>> i.e. "-" instead of "+" here ----------------^
> 
> The parentheses and indentation were misleading actually, here is how it
> should actually looks like:
> 
>>> +	m->m_data -= sizeof(struct tcpiphdr) - ( sizeof(struct ip)
>>> +	                                         + sizeof(struct tcphdr));
> 
> I've now dropped the parentheses, so it looks like the tcp_output.c code:
> 
> 	m->m_data -= sizeof(struct tcpiphdr) - sizeof(struct ip)
> 	                                     - sizeof(struct tcphdr);

Ah, sorry, I indeed simply got confused because it was written in two
different ways :-/ ... would it maybe be applicable to use the
TCPIPHDR_DELTA macro here instead?

Apart from that, the patch looks ok to me.

 Thomas
Samuel Thibault Feb. 22, 2016, 10:20 a.m. UTC | #5 
Hello,

Thomas Huth, on Mon 22 Feb 2016 08:56:59 +0100, wrote:
> would it maybe be applicable to use the
> TCPIPHDR_DELTA macro here instead?

No, because that includes a round up, while here we need an exact
difference.

Samuel
diff mbox

Patch

diff --git a/slirp/if.h b/slirp/if.h
index 3327023..c7a5c57 100644
--- a/slirp/if.h
+++ b/slirp/if.h
@@ -17,7 +17,7 @@ 
 #define IF_MRU 1500
 #define	IF_COMP IF_AUTOCOMP	/* Flags for compression */
 
-/* 2 for alignment, 14 for ethernet, 40 for TCP/IP */
-#define IF_MAXLINKHDR (2 + 14 + 40)
+/* 2 for alignment, 14 for ethernet */
+#define IF_MAXLINKHDR (2 + ETH_HLEN)
 
 #endif
diff --git a/slirp/mbuf.c b/slirp/mbuf.c
index c959758..f081c69 100644
--- a/slirp/mbuf.c
+++ b/slirp/mbuf.c
@@ -24,7 +24,8 @@ 
  * Find a nice value for msize
  * XXX if_maxlinkhdr already in mtu
  */
-#define SLIRP_MSIZE (IF_MTU + IF_MAXLINKHDR + offsetof(struct mbuf, m_dat) + 6)
+#define SLIRP_MSIZE\
+    (offsetof(struct mbuf, m_dat) + IF_MAXLINKHDR + TCPIPHDR_DELTA + IF_MTU)
 
 void
 m_init(Slirp *slirp)
diff --git a/slirp/slirp.c b/slirp/slirp.c
index 5f42ada..c2c4597 100644
--- a/slirp/slirp.c
+++ b/slirp/slirp.c
@@ -754,15 +754,16 @@  void slirp_input(Slirp *slirp, const uint8_t *pkt, int pkt_len)
         m = m_get(slirp);
         if (!m)
             return;
-        /* Note: we add to align the IP header */
-        if (M_FREEROOM(m) < pkt_len + 2) {
-            m_inc(m, pkt_len + 2);
+        /* Note: we add 2 to align the IP header on 4 bytes,
+         * and add the margin for the tcpiphdr overhead  */
+        if (M_FREEROOM(m) < pkt_len + TCPIPHDR_DELTA + 2) {
+            m_inc(m, pkt_len + TCPIPHDR_DELTA + 2);
         }
-        m->m_len = pkt_len + 2;
-        memcpy(m->m_data + 2, pkt, pkt_len);
+        m->m_len = pkt_len + TCPIPHDR_DELTA + 2;
+        memcpy(m->m_data + TCPIPHDR_DELTA + 2, pkt, pkt_len);
 
-        m->m_data += 2 + ETH_HLEN;
-        m->m_len -= 2 + ETH_HLEN;
+        m->m_data += TCPIPHDR_DELTA + 2 + ETH_HLEN;
+        m->m_len -= TCPIPHDR_DELTA + 2 + ETH_HLEN;
 
         if (proto == ETH_P_IP) {
             ip_input(m);
diff --git a/slirp/socket.c b/slirp/socket.c
index b79ddec..d4b02c8 100644
--- a/slirp/socket.c
+++ b/slirp/socket.c
@@ -483,7 +483,18 @@  sorecvfrom(struct socket *so)
 	  if (!m) {
 	      return;
 	  }
-	  m->m_data += IF_MAXLINKHDR;
+	  switch (so->so_ffamily) {
+	  case AF_INET:
+	      m->m_data += IF_MAXLINKHDR + sizeof(struct udpiphdr);
+	      break;
+	  case AF_INET6:
+	      m->m_data += IF_MAXLINKHDR + sizeof(struct ip6)
+	                                 + sizeof(struct udphdr);
+	      break;
+	  default:
+	      g_assert_not_reached();
+	      break;
+	  }
 
 	  /*
 	   * XXX Shouldn't FIONREAD packets destined for port 53,
diff --git a/slirp/tcp_input.c b/slirp/tcp_input.c
index 5f845da..26b0c8b 100644
--- a/slirp/tcp_input.c
+++ b/slirp/tcp_input.c
@@ -256,11 +256,6 @@  tcp_input(struct mbuf *m, int iphlen, struct socket *inso)
 	}
 	slirp = m->slirp;
 
-	/*
-	 * Get IP and TCP header together in first mbuf.
-	 * Note: IP leaves IP header in first mbuf.
-	 */
-	ti = mtod(m, struct tcpiphdr *);
 	if (iphlen > sizeof(struct ip )) {
 	  ip_stripoptions(m, (struct mbuf *)0);
 	  iphlen=sizeof(struct ip );
@@ -277,14 +272,28 @@  tcp_input(struct mbuf *m, int iphlen, struct socket *inso)
 	save_ip.ip_len+= iphlen;
 
 	/*
+	 * Get IP and TCP header together in first mbuf.
+	 * Note: IP leaves IP header in first mbuf.
+	 */
+	m->m_data -= sizeof(struct tcpiphdr) - (sizeof(struct ip)
+	                                     + sizeof(struct tcphdr));
+	m->m_len += sizeof(struct tcpiphdr) - (sizeof(struct ip)
+	                                    + sizeof(struct tcphdr));
+	ti = mtod(m, struct tcpiphdr *);
+
+	/*
 	 * Checksum extended TCP header and data.
 	 */
-	tlen = ((struct ip *)ti)->ip_len;
-        tcpiphdr2qlink(ti)->next = tcpiphdr2qlink(ti)->prev = NULL;
-        memset(&ti->ti_i.ih_mbuf, 0 , sizeof(struct mbuf_ptr));
-	ti->ti_x1 = 0;
+	tlen = ip->ip_len;
+	tcpiphdr2qlink(ti)->next = tcpiphdr2qlink(ti)->prev = NULL;
+	memset(&ti->ih_mbuf, 0 , sizeof(struct mbuf_ptr));
+	memset(&ti->ti, 0, sizeof(ti->ti));
+	ti->ti_x0 = 0;
+	ti->ti_src = save_ip.ip_src;
+	ti->ti_dst = save_ip.ip_dst;
+	ti->ti_pr = save_ip.ip_p;
 	ti->ti_len = htons((uint16_t)tlen);
-	len = sizeof(struct ip ) + tlen;
+	len = ((sizeof(struct tcpiphdr) - sizeof(struct tcphdr)) + tlen);
 	if(cksum(m, len)) {
 	  goto drop;
 	}
@@ -1475,7 +1484,7 @@  tcp_mss(struct tcpcb *tp, u_int offer)
 	DEBUG_ARG("tp = %p", tp);
 	DEBUG_ARG("offer = %d", offer);
 
-	mss = min(IF_MTU, IF_MRU) - sizeof(struct tcpiphdr);
+	mss = min(IF_MTU, IF_MRU) - sizeof(struct tcphdr) + sizeof(struct ip);
 	if (offer)
 		mss = min(mss, offer);
 	mss = max(mss, 32);
diff --git a/slirp/tcp_output.c b/slirp/tcp_output.c
index 34e4d2e..7fc6a87 100644
--- a/slirp/tcp_output.c
+++ b/slirp/tcp_output.c
@@ -448,15 +448,23 @@  send:
 	 */
 	m->m_len = hdrlen + len; /* XXX Needed? m_len should be correct */
 
-    {
+	struct tcpiphdr tcpiph_save = *(mtod(m, struct tcpiphdr *));
+	m->m_data += sizeof(struct tcpiphdr) - sizeof(struct tcphdr)
+	                                     - sizeof(struct ip);
+	m->m_len  -= sizeof(struct tcpiphdr) - sizeof(struct tcphdr)
+	                                     - sizeof(struct ip);
+	struct ip *ip = mtod(m, struct ip *);
 
-	((struct ip *)ti)->ip_len = m->m_len;
+	ip->ip_len = m->m_len;
+	ip->ip_dst = tcpiph_save.ti_dst;
+	ip->ip_src = tcpiph_save.ti_src;
+	ip->ip_p = tcpiph_save.ti_pr;
 
-	((struct ip *)ti)->ip_ttl = IPDEFTTL;
-	((struct ip *)ti)->ip_tos = so->so_iptos;
+	ip->ip_ttl = IPDEFTTL;
+	ip->ip_tos = so->so_iptos;
 
 	error = ip_output(so, m);
-    }
+
 	if (error) {
 out:
 		return (error);
diff --git a/slirp/tcp_subr.c b/slirp/tcp_subr.c
index b1aa1f2..cd021df 100644
--- a/slirp/tcp_subr.c
+++ b/slirp/tcp_subr.c
@@ -76,9 +76,10 @@  tcp_template(struct tcpcb *tp)
 	register struct tcpiphdr *n = &tp->t_template;
 
 	n->ti_mbuf = NULL;
-	n->ti_x1 = 0;
+	memset(&n->ti, 0, sizeof(n->ti));
+	n->ti_x0 = 0;
 	n->ti_pr = IPPROTO_TCP;
-	n->ti_len = htons(sizeof (struct tcpiphdr) - sizeof (struct ip));
+	n->ti_len = htons(sizeof(struct tcphdr));
 	n->ti_src = so->so_faddr;
 	n->ti_dst = so->so_laddr;
 	n->ti_sport = so->so_fport;
@@ -131,6 +132,7 @@  tcp_respond(struct tcpcb *tp, struct tcpiphdr *ti, struct mbuf *m,
 		m->m_data += IF_MAXLINKHDR;
 		*mtod(m, struct tcpiphdr *) = *ti;
 		ti = mtod(m, struct tcpiphdr *);
+		memset(&ti->ti, 0, sizeof(ti->ti));
 		flags = TH_ACK;
 	} else {
 		/*
@@ -150,8 +152,8 @@  tcp_respond(struct tcpcb *tp, struct tcpiphdr *ti, struct mbuf *m,
 	tlen += sizeof (struct tcpiphdr);
 	m->m_len = tlen;
 
-        ti->ti_mbuf = NULL;
-	ti->ti_x1 = 0;
+	ti->ti_mbuf = NULL;
+	ti->ti_x0 = 0;
 	ti->ti_seq = htonl(seq);
 	ti->ti_ack = htonl(ack);
 	ti->ti_x2 = 0;
@@ -164,12 +166,23 @@  tcp_respond(struct tcpcb *tp, struct tcpiphdr *ti, struct mbuf *m,
 	ti->ti_urp = 0;
 	ti->ti_sum = 0;
 	ti->ti_sum = cksum(m, tlen);
-	((struct ip *)ti)->ip_len = tlen;
 
-	if(flags & TH_RST)
-	  ((struct ip *)ti)->ip_ttl = MAXTTL;
-	else
-	  ((struct ip *)ti)->ip_ttl = IPDEFTTL;
+	struct tcpiphdr tcpiph_save = *(mtod(m, struct tcpiphdr *));
+	m->m_data += sizeof(struct tcpiphdr) - sizeof(struct tcphdr)
+	                                     - sizeof(struct ip);
+	m->m_len  -= sizeof(struct tcpiphdr) - sizeof(struct tcphdr)
+	                                     - sizeof(struct ip);
+	struct ip *ip = mtod(m, struct ip *);
+	ip->ip_len = tlen;
+	ip->ip_dst = tcpiph_save.ti_dst;
+	ip->ip_src = tcpiph_save.ti_src;
+	ip->ip_p = tcpiph_save.ti_pr;
+
+	if (flags & TH_RST) {
+		ip->ip_ttl = MAXTTL;
+	} else {
+		ip->ip_ttl = IPDEFTTL;
+	}
 
 	(void) ip_output((struct socket *)0, m);
 }
diff --git a/slirp/tcpip.h b/slirp/tcpip.h
index 7974ce3..3c5d127 100644
--- a/slirp/tcpip.h
+++ b/slirp/tcpip.h
@@ -37,15 +37,23 @@ 
  * Tcp+ip header, after ip options removed.
  */
 struct tcpiphdr {
-	struct 	ipovly ti_i;		/* overlaid ip structure */
-	struct	tcphdr ti_t;		/* tcp header */
+    struct mbuf_ptr ih_mbuf;	/* backpointer to mbuf */
+    union {
+        struct {
+            struct  in_addr ih_src; /* source internet address */
+            struct  in_addr ih_dst; /* destination internet address */
+            uint8_t ih_x1;          /* (unused) */
+            uint8_t ih_pr;          /* protocol */
+        } ti_i4;
+    } ti;
+    uint16_t    ti_x0;
+    uint16_t    ti_len;             /* protocol length */
+    struct      tcphdr ti_t;        /* tcp header */
 };
-#define	ti_mbuf		ti_i.ih_mbuf.mptr
-#define	ti_x1		ti_i.ih_x1
-#define	ti_pr		ti_i.ih_pr
-#define	ti_len		ti_i.ih_len
-#define	ti_src		ti_i.ih_src
-#define	ti_dst		ti_i.ih_dst
+#define	ti_mbuf		ih_mbuf.mptr
+#define	ti_pr		ti.ti_i4.ih_pr
+#define	ti_src		ti.ti_i4.ih_src
+#define	ti_dst		ti.ti_i4.ih_dst
 #define	ti_sport	ti_t.th_sport
 #define	ti_dport	ti_t.th_dport
 #define	ti_seq		ti_t.th_seq
@@ -65,6 +73,13 @@  struct tcpiphdr {
 #define tcpfrag_list_end(F, T) (tcpiphdr2qlink(F) == (struct qlink*)(T))
 #define tcpfrag_list_empty(T) ((T)->seg_next == (struct tcpiphdr*)(T))
 
+/* This is the difference between the size of a tcpiphdr structure, and the
+ * size of actual ip+tcp headers, rounded up since we need to align data.  */
+#define TCPIPHDR_DELTA\
+    (max(0,\
+         (sizeof(struct tcpiphdr)\
+          - sizeof(struct ip) - sizeof(struct tcphdr) + 3) & ~3))
+
 /*
  * Just a clean way to get to the first byte
  * of the packet