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slirp: Factorizing tcpiphdr structure with an union
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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>
Reviewed-by: Thomas Huth <thuth@redhat.com>
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@sthibaul
Guillaume Subiron authored and sthibaul committed Mar 15, 2016
1 parent 15d62af commit 98c6305
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Showing 8 changed files with 106 additions and 45 deletions.
4 changes: 2 additions & 2 deletions slirp/if.h
View file
Expand Up @@ -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
4 changes: 2 additions & 2 deletions slirp/mbuf.c
View file
Expand Up @@ -22,9 +22,9 @@

/*
* 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)
Expand Down
15 changes: 8 additions & 7 deletions slirp/slirp.c
View file
Expand Up @@ -766,15 +766,16 @@ 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);
Expand Down
13 changes: 12 additions & 1 deletion slirp/socket.c
View file
Expand Up @@ -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,
Expand Down
35 changes: 24 additions & 11 deletions slirp/tcp_input.c
View file
Expand Up @@ -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 );
Expand All @@ -276,15 +271,29 @@ tcp_input(struct mbuf *m, int iphlen, struct socket *inso)
save_ip = *ip;
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;
}
Expand Down Expand Up @@ -603,6 +612,10 @@ tcp_input(struct mbuf *m, int iphlen, struct socket *inso)
HTONS(ti->ti_urp);
m->m_data -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
m->m_len += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
m->m_data += sizeof(struct tcpiphdr) - sizeof(struct ip)
- sizeof(struct tcphdr);
m->m_len -= sizeof(struct tcpiphdr) - sizeof(struct ip)
- sizeof(struct tcphdr);
*ip=save_ip;
icmp_send_error(m, ICMP_UNREACH, code, 0, strerror(errno));
}
Expand Down Expand Up @@ -1471,7 +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);
Expand Down
18 changes: 13 additions & 5 deletions slirp/tcp_output.c
View file
Expand Up @@ -448,15 +448,23 @@ tcp_output(struct tcpcb *tp)
*/
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);
Expand Down
31 changes: 22 additions & 9 deletions slirp/tcp_subr.c
View file
Expand Up @@ -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;
Expand Down Expand Up @@ -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 {
/*
Expand All @@ -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;
Expand All @@ -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);
}
Expand Down
31 changes: 23 additions & 8 deletions slirp/tcpip.h
View file
Expand Up @@ -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
Expand All @@ -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
Expand Down

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