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| author | Eric Dumazet <edumazet@google.com> | 2024-04-07 09:33:22 +0000 |
|---|---|---|
| committer | Paolo Abeni <pabeni@redhat.com> | 2024-04-09 11:47:40 +0200 |
| commit | 41eecbd712b73f0d5dcf1152b9a1c27b1f238028 (patch) | |
| tree | 3536f6f2395edecdf28f4a9ce3357d0aba56c68f /net/ipv6/tcp_ipv6.c | |
| parent | b9e810405880c99baafd550ada7043e86465396e (diff) | |
| download | linux-stable-41eecbd712b73f0d5dcf1152b9a1c27b1f238028.tar.gz linux-stable-41eecbd712b73f0d5dcf1152b9a1c27b1f238028.tar.bz2 linux-stable-41eecbd712b73f0d5dcf1152b9a1c27b1f238028.zip | |
tcp: replace TCP_SKB_CB(skb)->tcp_tw_isn with a per-cpu field
TCP can transform a TIMEWAIT socket into a SYN_RECV one from
a SYN packet, and the ISN of the SYNACK packet is normally
generated using TIMEWAIT tw_snd_nxt :
tcp_timewait_state_process()
...
u32 isn = tcptw->tw_snd_nxt + 65535 + 2;
if (isn == 0)
isn++;
TCP_SKB_CB(skb)->tcp_tw_isn = isn;
return TCP_TW_SYN;
This SYN packet also bypasses normal checks against listen queue
being full or not.
tcp_conn_request()
...
__u32 isn = TCP_SKB_CB(skb)->tcp_tw_isn;
...
/* TW buckets are converted to open requests without
* limitations, they conserve resources and peer is
* evidently real one.
*/
if ((syncookies == 2 || inet_csk_reqsk_queue_is_full(sk)) && !isn) {
want_cookie = tcp_syn_flood_action(sk, rsk_ops->slab_name);
if (!want_cookie)
goto drop;
}
This was using TCP_SKB_CB(skb)->tcp_tw_isn field in skb.
Unfortunately this field has been accidentally cleared
after the call to tcp_timewait_state_process() returning
TCP_TW_SYN.
Using a field in TCP_SKB_CB(skb) for a temporary state
is overkill.
Switch instead to a per-cpu variable.
As a bonus, we do not have to clear tcp_tw_isn in TCP receive
fast path.
It is temporarily set then cleared only in the TCP_TW_SYN dance.
Fixes: 4ad19de8774e ("net: tcp6: fix double call of tcp_v6_fill_cb()")
Fixes: eeea10b83a13 ("tcp: add tcp_v4_fill_cb()/tcp_v4_restore_cb()")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Diffstat (limited to 'net/ipv6/tcp_ipv6.c')
| -rw-r--r-- | net/ipv6/tcp_ipv6.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index 5141f7033abd..3aa9da5c9a66 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -1741,7 +1741,6 @@ static void tcp_v6_fill_cb(struct sk_buff *skb, const struct ipv6hdr *hdr, skb->len - th->doff*4); TCP_SKB_CB(skb)->ack_seq = ntohl(th->ack_seq); TCP_SKB_CB(skb)->tcp_flags = tcp_flag_byte(th); - TCP_SKB_CB(skb)->tcp_tw_isn = 0; TCP_SKB_CB(skb)->ip_dsfield = ipv6_get_dsfield(hdr); TCP_SKB_CB(skb)->sacked = 0; TCP_SKB_CB(skb)->has_rxtstamp = @@ -1758,6 +1757,7 @@ INDIRECT_CALLABLE_SCOPE int tcp_v6_rcv(struct sk_buff *skb) bool refcounted; struct sock *sk; int ret; + u32 isn; struct net *net = dev_net(skb->dev); drop_reason = SKB_DROP_REASON_NOT_SPECIFIED; @@ -1967,7 +1967,7 @@ do_time_wait: goto csum_error; } - switch (tcp_timewait_state_process(inet_twsk(sk), skb, th)) { + switch (tcp_timewait_state_process(inet_twsk(sk), skb, th, &isn)) { case TCP_TW_SYN: { struct sock *sk2; @@ -1985,6 +1985,7 @@ do_time_wait: sk = sk2; tcp_v6_restore_cb(skb); refcounted = false; + __this_cpu_write(tcp_tw_isn, isn); goto process; } } |