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tap: Fill the IPv6 flow label field to represent flow association

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This isn't optional: TCP streams must carry a unique, hard-to-guess,
non-zero label for each direction. Linux, probably among others,
will otherwise refuse to associate packets in a given stream to the
same connection.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
Stefano Brivio 2021-07-26 07:30:57 +02:00
parent 17765f8de0
commit 16b08367a5
5 changed files with 25 additions and 10 deletions
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4
dhcpv6.c
View file

@ -520,7 +520,7 @@ int dhcpv6(struct ctx *c, struct ethhdr *eh, size_t len)
resp_not_on_link.hdr.xid = mh->xid;
tap_ip_send(c, &c->gw6, IPPROTO_UDP,
(char *)&resp_not_on_link, n);
(char *)&resp_not_on_link, n, mh->xid);
return 1;
}
@ -569,7 +569,7 @@ int dhcpv6(struct ctx *c, struct ethhdr *eh, size_t len)
resp.hdr.xid = mh->xid;
tap_ip_send(c, &c->gw6, IPPROTO_UDP, (char *)&resp, n);
tap_ip_send(c, &c->gw6, IPPROTO_UDP, (char *)&resp, n, mh->xid);
c->addr6_seen = c->addr6;
return 1;

4
icmp.c
View file

@ -98,7 +98,7 @@ void icmp_sock_handler(struct ctx *c, union epoll_ref ref, uint32_t events,
icmp_id_map[V6][id].seq = seq;
}
tap_ip_send(c, &sr6->sin6_addr, IPPROTO_ICMPV6, buf, n);
tap_ip_send(c, &sr6->sin6_addr, IPPROTO_ICMPV6, buf, n, 0);
} else {
struct sockaddr_in *sr4 = (struct sockaddr_in *)&sr;
struct icmphdr *ih = (struct icmphdr *)buf;
@ -115,7 +115,7 @@ void icmp_sock_handler(struct ctx *c, union epoll_ref ref, uint32_t events,
memcpy(&a6.s6_addr[12], &sr4->sin_addr, sizeof(sr4->sin_addr));
tap_ip_send(c, &a6, IPPROTO_ICMP, buf, n);
tap_ip_send(c, &a6, IPPROTO_ICMP, buf, n, 0);
}
}

18
tap.c
View file

@ -91,9 +91,10 @@ int tap_send(struct ctx *c, void *data, size_t len, int vnet_pre)
* @proto: L4 protocol number
* @in: Payload
* @len: L4 payload length
* @flow: Flow label for TCP over IPv6
*/
void tap_ip_send(struct ctx *c, struct in6_addr *src, uint8_t proto,
char *in, size_t len)
char *in, size_t len, uint32_t flow)
{
char buf[USHRT_MAX];
char *pkt = buf + 4;
@ -161,21 +162,30 @@ void tap_ip_send(struct ctx *c, struct in6_addr *src, uint8_t proto,
struct tcphdr *th = (struct tcphdr *)(ip6h + 1);
th->check = 0;
th->check = csum_ip4(ip6h, len + sizeof(*ip6h));
th->check = csum_unaligned(ip6h, len + sizeof(*ip6h),
0);
} else if (proto == IPPROTO_UDP) {
struct udphdr *uh = (struct udphdr *)(ip6h + 1);
uh->check = 0;
uh->check = csum_ip4(ip6h, len + sizeof(*ip6h));
uh->check = csum_unaligned(ip6h, len + sizeof(*ip6h),
0);
} else if (proto == IPPROTO_ICMPV6) {
struct icmp6hdr *ih = (struct icmp6hdr *)(ip6h + 1);
ih->icmp6_cksum = 0;
ih->icmp6_cksum = csum_ip4(ip6h, len + sizeof(*ip6h));
ih->icmp6_cksum = csum_unaligned(ip6h,
len + sizeof(*ip6h),
0);
}
ip6h->version = 6;
ip6h->nexthdr = proto;
ip6h->hop_limit = 255;
if (flow) {
ip6h->flow_lbl[0] = (flow >> 16) & 0xf;
ip6h->flow_lbl[1] = (flow >> 8) & 0xff;
ip6h->flow_lbl[2] = (flow >> 0) & 0xff;
}
tap_send(c, buf, len + sizeof(*ip6h) + sizeof(*eh), 1);
}

2
tap.h
View file

@ -1,5 +1,5 @@
void tap_ip_send(struct ctx *c, struct in6_addr *src, uint8_t proto,
char *in, size_t len);
char *in, size_t len, uint32_t flow);
int tap_send(struct ctx *c, void *data, size_t len, int vnet_pre);
void tap_handler(struct ctx *c, uint32_t events, struct timespec *now);
void tap_sock_init(struct ctx *c);

7
tcp.c
View file

@ -469,6 +469,7 @@ struct tcp_tap_conn {
uint32_t seq_from_tap;
uint32_t seq_ack_to_tap;
uint32_t seq_init_from_tap;
uint32_t seq_init_to_tap;
uint64_t tcpi_acked_last;
int ws_allowed;
@ -934,7 +935,8 @@ static int tcp_send_to_tap(struct ctx *c, struct tcp_tap_conn *conn,
memcpy(data, in, len);
tap_ip_send(c, &conn->a.a6, IPPROTO_TCP, buf, th->doff * 4 + len);
tap_ip_send(c, &conn->a.a6, IPPROTO_TCP, buf, th->doff * 4 + len,
conn->seq_init_to_tap);
return 0;
}
@ -1116,6 +1118,7 @@ static void tcp_conn_from_tap(struct ctx *c, int af, void *addr,
conn->seq_ack_to_tap = conn->seq_from_tap;
conn->seq_to_tap = tcp_seq_init(c, af, addr, th->dest, th->source, now);
conn->seq_init_to_tap = conn->seq_to_tap;
conn->seq_ack_from_tap = conn->seq_to_tap + 1;
tcp_hash_insert(c, conn, af, addr);
@ -1828,6 +1831,7 @@ static void tcp_conn_from_sock(struct ctx *c, union epoll_ref ref,
conn->sock_port,
conn->tap_port,
now);
conn->seq_init_to_tap = conn->seq_to_tap;
tcp_hash_insert(c, conn, AF_INET6, &sa6->sin6_addr);
} else {
@ -1850,6 +1854,7 @@ static void tcp_conn_from_sock(struct ctx *c, union epoll_ref ref,
conn->sock_port,
conn->tap_port,
now);
conn->seq_init_to_tap = conn->seq_to_tap;
tcp_hash_insert(c, conn, AF_INET, &sa4->sin_addr);
}