Found that when randomized tcp offsets are enabled (by default)
TCP client can still start new connections without them. Later,
if server does active close and re-uses sockets in TIME-WAIT
state, new SYN from client can be rejected on PAWS check inside
tcp_timewait_state_process(), because either tw_ts_recent or
rcv_tsval doesn't really have an offset set.
Here is how to reproduce it with LTP netstress tool:
netstress -R 1 &
netstress -H 127.0.0.1 -lr
1000000 -a1
[...]
< S seq
1956977072 win 43690 TS val 295618 ecr
459956970
> . ack
1956911535 win 342 TS val
459967184 ecr
1547117608
< R seq
1956911535 win 0 length 0
+1. < S seq
1956977072 win 43690 TS val 296640 ecr
459956970
> S. seq
657450664 ack
1956977073 win 43690 TS val
459968205 ecr 296640
Fixes:
95a22caee396 ("tcp: randomize tcp timestamp offsets for each connection")
Signed-off-by: Alexey Kodanev <alexey.kodanev@oracle.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
struct flowi4 *fl4;
struct rtable *rt;
int err;
+ u32 seq;
struct ip_options_rcu *inet_opt;
struct inet_timewait_death_row *tcp_death_row = &sock_net(sk)->ipv4.tcp_death_row;
sk_setup_caps(sk, &rt->dst);
rt = NULL;
- if (!tp->write_seq && likely(!tp->repair))
- tp->write_seq = secure_tcp_sequence_number(inet->inet_saddr,
- inet->inet_daddr,
- inet->inet_sport,
- usin->sin_port,
- &tp->tsoffset);
+ if (likely(!tp->repair)) {
+ seq = secure_tcp_sequence_number(inet->inet_saddr,
+ inet->inet_daddr,
+ inet->inet_sport,
+ usin->sin_port,
+ &tp->tsoffset);
+ if (!tp->write_seq)
+ tp->write_seq = seq;
+ }
inet->inet_id = tp->write_seq ^ jiffies;
struct flowi6 fl6;
struct dst_entry *dst;
int addr_type;
+ u32 seq;
int err;
struct inet_timewait_death_row *tcp_death_row = &sock_net(sk)->ipv4.tcp_death_row;
sk_set_txhash(sk);
- if (!tp->write_seq && likely(!tp->repair))
- tp->write_seq = secure_tcpv6_sequence_number(np->saddr.s6_addr32,
- sk->sk_v6_daddr.s6_addr32,
- inet->inet_sport,
- inet->inet_dport,
- &tp->tsoffset);
+ if (likely(!tp->repair)) {
+ seq = secure_tcpv6_sequence_number(np->saddr.s6_addr32,
+ sk->sk_v6_daddr.s6_addr32,
+ inet->inet_sport,
+ inet->inet_dport,
+ &tp->tsoffset);
+ if (!tp->write_seq)
+ tp->write_seq = seq;
+ }
if (tcp_fastopen_defer_connect(sk, &err))
return err;