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tcp, udp: Don't pre-fill IPv4 destination address in headers

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Because packets sent on the tap interface will always be going to the
guest/namespace, we more-or-less know what address they'll be going to.  So
we pre-fill this destination address in our header buffers for IPv4.  We
can't do the same for IPv6 because we could need either the global or
link-local address for the guest.  In future we're going to want more
flexibility for the destination address, so this pre-filling will get in
the way.

Change the flow so we always fill in the IPv4 destination address for each
packet, rather than prefilling it from proto_update_l2_buf().  In fact for
TCP we already redundantly filled the destination for each packet anyway.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
David Gibson 2023-08-22 15:29:57 +10:00 committed by Stefano Brivio
parent 5bf200ae8a
commit 955dd3251c
8 changed files with 15 additions and 32 deletions
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10
passt.c
View file

@ -117,13 +117,11 @@ static void timer_init(struct ctx *c, const struct timespec *now)
* proto_update_l2_buf() - Update scatter-gather L2 buffers in protocol handlers * proto_update_l2_buf() - Update scatter-gather L2 buffers in protocol handlers
* @eth_d: Ethernet destination address, NULL if unchanged * @eth_d: Ethernet destination address, NULL if unchanged
* @eth_s: Ethernet source address, NULL if unchanged * @eth_s: Ethernet source address, NULL if unchanged
* @ip_da: Pointer to IPv4 destination address, NULL if unchanged
*/ */
void proto_update_l2_buf(const unsigned char *eth_d, const unsigned char *eth_s, void proto_update_l2_buf(const unsigned char *eth_d, const unsigned char *eth_s)
const struct in_addr *ip_da)
{ {
tcp_update_l2_buf(eth_d, eth_s, ip_da); tcp_update_l2_buf(eth_d, eth_s);
udp_update_l2_buf(eth_d, eth_s, ip_da); udp_update_l2_buf(eth_d, eth_s);
} }
/** /**
@ -247,7 +245,7 @@ int main(int argc, char **argv)
if (!c.no_icmp) if (!c.no_icmp)
icmp_init(); icmp_init();
proto_update_l2_buf(c.mac_guest, c.mac, &c.ip4.addr); proto_update_l2_buf(c.mac_guest, c.mac);
if (c.ifi4 && !c.no_dhcp) if (c.ifi4 && !c.no_dhcp)
dhcp_init(); dhcp_init();

4
passt.h
View file

@ -303,7 +303,7 @@ struct ctx {
int low_rmem; int low_rmem;
}; };
void proto_update_l2_buf(const unsigned char *eth_d, const unsigned char *eth_s, void proto_update_l2_buf(const unsigned char *eth_d,
const struct in_addr *ip_da); const unsigned char *eth_s);
#endif /* PASST_H */ #endif /* PASST_H */

2
pasta.c
View file

@ -353,7 +353,7 @@ void pasta_ns_conf(struct ctx *c)
} }
} }
proto_update_l2_buf(c->mac_guest, NULL, NULL); proto_update_l2_buf(c->mac_guest, NULL);
} }
/** /**

8
tap.c
View file

@ -625,10 +625,8 @@ resume:
l4_len = l3_len - hlen; l4_len = l3_len - hlen;
if (iph->saddr && c->ip4.addr_seen.s_addr != iph->saddr) { if (iph->saddr && c->ip4.addr_seen.s_addr != iph->saddr)
c->ip4.addr_seen.s_addr = iph->saddr; c->ip4.addr_seen.s_addr = iph->saddr;
proto_update_l2_buf(NULL, NULL, &c->ip4.addr_seen);
}
l4h = packet_get(in, i, sizeof(*eh) + hlen, l4_len, NULL); l4h = packet_get(in, i, sizeof(*eh) + hlen, l4_len, NULL);
if (!l4h) if (!l4h)
@ -969,7 +967,7 @@ redo:
if (memcmp(c->mac_guest, eh->h_source, ETH_ALEN)) { if (memcmp(c->mac_guest, eh->h_source, ETH_ALEN)) {
memcpy(c->mac_guest, eh->h_source, ETH_ALEN); memcpy(c->mac_guest, eh->h_source, ETH_ALEN);
proto_update_l2_buf(c->mac_guest, NULL, NULL); proto_update_l2_buf(c->mac_guest, NULL);
} }
switch (ntohs(eh->h_proto)) { switch (ntohs(eh->h_proto)) {
@ -1030,7 +1028,7 @@ restart:
if (memcmp(c->mac_guest, eh->h_source, ETH_ALEN)) { if (memcmp(c->mac_guest, eh->h_source, ETH_ALEN)) {
memcpy(c->mac_guest, eh->h_source, ETH_ALEN); memcpy(c->mac_guest, eh->h_source, ETH_ALEN);
proto_update_l2_buf(c->mac_guest, NULL, NULL); proto_update_l2_buf(c->mac_guest, NULL);
} }
switch (ntohs(eh->h_proto)) { switch (ntohs(eh->h_proto)) {

8
tcp.c
View file

@ -997,10 +997,8 @@ static void tcp_update_check_tcp6(struct tcp6_l2_buf_t *buf)
* tcp_update_l2_buf() - Update L2 buffers with Ethernet and IPv4 addresses * tcp_update_l2_buf() - Update L2 buffers with Ethernet and IPv4 addresses
* @eth_d: Ethernet destination address, NULL if unchanged * @eth_d: Ethernet destination address, NULL if unchanged
* @eth_s: Ethernet source address, NULL if unchanged * @eth_s: Ethernet source address, NULL if unchanged
* @ip_da: Pointer to IPv4 destination address, NULL if unchanged
*/ */
void tcp_update_l2_buf(const unsigned char *eth_d, const unsigned char *eth_s, void tcp_update_l2_buf(const unsigned char *eth_d, const unsigned char *eth_s)
const struct in_addr *ip_da)
{ {
int i; int i;
@ -1014,10 +1012,6 @@ void tcp_update_l2_buf(const unsigned char *eth_d, const unsigned char *eth_s,
tap_update_mac(&b6->taph, eth_d, eth_s); tap_update_mac(&b6->taph, eth_d, eth_s);
tap_update_mac(&b4f->taph, eth_d, eth_s); tap_update_mac(&b4f->taph, eth_d, eth_s);
tap_update_mac(&b6f->taph, eth_d, eth_s); tap_update_mac(&b6f->taph, eth_d, eth_s);
if (ip_da) {
b4f->iph.daddr = b4->iph.daddr = ip_da->s_addr;
}
} }
} }

3
tcp.h
View file

@ -26,8 +26,7 @@ void tcp_timer(struct ctx *c, const struct timespec *ts);
void tcp_defer_handler(struct ctx *c); void tcp_defer_handler(struct ctx *c);
void tcp_sock_set_bufsize(const struct ctx *c, int s); void tcp_sock_set_bufsize(const struct ctx *c, int s);
void tcp_update_l2_buf(const unsigned char *eth_d, const unsigned char *eth_s, void tcp_update_l2_buf(const unsigned char *eth_d, const unsigned char *eth_s);
const struct in_addr *ip_da);
/** /**
* union tcp_epoll_ref - epoll reference portion for TCP connections * union tcp_epoll_ref - epoll reference portion for TCP connections

9
udp.c
View file

@ -276,10 +276,8 @@ static void udp_update_check4(struct udp4_l2_buf_t *buf)
* udp_update_l2_buf() - Update L2 buffers with Ethernet and IPv4 addresses * udp_update_l2_buf() - Update L2 buffers with Ethernet and IPv4 addresses
* @eth_d: Ethernet destination address, NULL if unchanged * @eth_d: Ethernet destination address, NULL if unchanged
* @eth_s: Ethernet source address, NULL if unchanged * @eth_s: Ethernet source address, NULL if unchanged
* @ip_da: Pointer to IPv4 destination address, NULL if unchanged
*/ */
void udp_update_l2_buf(const unsigned char *eth_d, const unsigned char *eth_s, void udp_update_l2_buf(const unsigned char *eth_d, const unsigned char *eth_s)
const struct in_addr *ip_da)
{ {
int i; int i;
@ -289,10 +287,6 @@ void udp_update_l2_buf(const unsigned char *eth_d, const unsigned char *eth_s,
tap_update_mac(&b4->taph, eth_d, eth_s); tap_update_mac(&b4->taph, eth_d, eth_s);
tap_update_mac(&b6->taph, eth_d, eth_s); tap_update_mac(&b6->taph, eth_d, eth_s);
if (ip_da) {
b4->iph.daddr = ip_da->s_addr;
}
} }
} }
@ -578,6 +572,7 @@ static size_t udp_update_hdr4(const struct ctx *c, int n, in_port_t dstport,
ip_len = udp4_l2_mh_sock[n].msg_len + sizeof(b->iph) + sizeof(b->uh); ip_len = udp4_l2_mh_sock[n].msg_len + sizeof(b->iph) + sizeof(b->uh);
b->iph.tot_len = htons(ip_len); b->iph.tot_len = htons(ip_len);
b->iph.daddr = c->ip4.addr_seen.s_addr;
src_port = ntohs(b->s_in.sin_port); src_port = ntohs(b->s_in.sin_port);

3
udp.h
View file

@ -16,8 +16,7 @@ int udp_sock_init(const struct ctx *c, int ns, sa_family_t af,
const void *addr, const char *ifname, in_port_t port); const void *addr, const char *ifname, in_port_t port);
int udp_init(struct ctx *c); int udp_init(struct ctx *c);
void udp_timer(struct ctx *c, const struct timespec *ts); void udp_timer(struct ctx *c, const struct timespec *ts);
void udp_update_l2_buf(const unsigned char *eth_d, const unsigned char *eth_s, void udp_update_l2_buf(const unsigned char *eth_d, const unsigned char *eth_s);
const struct in_addr *ip_da);
/** /**
* union udp_epoll_ref - epoll reference portion for TCP connections * union udp_epoll_ref - epoll reference portion for TCP connections