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tcp: fix syncookie regression

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commit ea4fc0d619 (ipv4: Don't use rt->rt_{src,dst} in ip_queue_xmit())
added a serious regression on synflood handling.

Simon Kirby discovered a successful connection was delayed by 20 seconds
before being responsive.

In my tests, I discovered that xmit frames were lost, and needed ~4
retransmits and a socket dst rebuild before being really sent.

In case of syncookie initiated connection, we use a different path to
initialize the socket dst, and inet->cork.fl.u.ip4 is left cleared.

As ip_queue_xmit() now depends on inet flow being setup, fix this by
copying the temp flowi4 we use in cookie_v4_check().

Reported-by: Simon Kirby <sim@netnation.com>
Bisected-by: Simon Kirby <sim@netnation.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Tested-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2012-03-10 09:20:21 +00:00 committed by David S. Miller
parent 4e50391968
commit dfd25ffffc
2 changed files with 23 additions and 17 deletions
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30
net/ipv4/syncookies.c
View file

@ -278,6 +278,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
struct rtable *rt;
__u8 rcv_wscale;
bool ecn_ok = false;
struct flowi4 fl4;
if (!sysctl_tcp_syncookies || !th->ack || th->rst)
goto out;
@ -346,20 +347,16 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
* hasn't changed since we received the original syn, but I see
* no easy way to do this.
*/
{
struct flowi4 fl4;
flowi4_init_output(&fl4, 0, sk->sk_mark, RT_CONN_FLAGS(sk),
RT_SCOPE_UNIVERSE, IPPROTO_TCP,
inet_sk_flowi_flags(sk),
(opt && opt->srr) ? opt->faddr : ireq->rmt_addr,
ireq->loc_addr, th->source, th->dest);
security_req_classify_flow(req, flowi4_to_flowi(&fl4));
rt = ip_route_output_key(sock_net(sk), &fl4);
if (IS_ERR(rt)) {
reqsk_free(req);
goto out;
}
flowi4_init_output(&fl4, 0, sk->sk_mark, RT_CONN_FLAGS(sk),
RT_SCOPE_UNIVERSE, IPPROTO_TCP,
inet_sk_flowi_flags(sk),
(opt && opt->srr) ? opt->faddr : ireq->rmt_addr,
ireq->loc_addr, th->source, th->dest);
security_req_classify_flow(req, flowi4_to_flowi(&fl4));
rt = ip_route_output_key(sock_net(sk), &fl4);
if (IS_ERR(rt)) {
reqsk_free(req);
goto out;
}
/* Try to redo what tcp_v4_send_synack did. */
@ -373,5 +370,10 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
ireq->rcv_wscale = rcv_wscale;
ret = get_cookie_sock(sk, skb, req, &rt->dst);
/* ip_queue_xmit() depends on our flow being setup
* Normal sockets get it right from inet_csk_route_child_sock()
*/
if (ret)
inet_sk(ret)->cork.fl.u.ip4 = fl4;
out: return ret;
}

10
net/ipv4/tcp_ipv4.c
View file

@ -1466,9 +1466,13 @@ struct sock *tcp_v4_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
inet_csk(newsk)->icsk_ext_hdr_len = inet_opt->opt.optlen;
newinet->inet_id = newtp->write_seq ^ jiffies;
if (!dst && (dst = inet_csk_route_child_sock(sk, newsk, req)) == NULL)
goto put_and_exit;
if (!dst) {
dst = inet_csk_route_child_sock(sk, newsk, req);
if (!dst)
goto put_and_exit;
} else {
/* syncookie case : see end of cookie_v4_check() */
}
sk_setup_caps(newsk, dst);
tcp_mtup_init(newsk);