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tcp: fix fastopen code vs usec TS 

After blamed commit, TFO client-ack-dropped-then-recovery-ms-timestamps
packetdrill test failed.

David Morley and Neal Cardwell started investigating and Neal pointed
that we had :

tcp_conn_request()
  tcp_try_fastopen()
   -> tcp_fastopen_create_child
     -> child = inet_csk(sk)->icsk_af_ops->syn_recv_sock()
       -> tcp_create_openreq_child()
          -> copy req_usec_ts from req:
          newtp->tcp_usec_ts = treq->req_usec_ts;
          // now the new TFO server socket always does usec TS, no matter
          // what the route options are...
  send_synack()
    -> tcp_make_synack()
        // disable tcp_rsk(req)->req_usec_ts if route option is not present:
        if (tcp_rsk(req)->req_usec_ts < 0)
                tcp_rsk(req)->req_usec_ts = dst_tcp_usec_ts(dst);

tcp_conn_request() has the initial dst, we can initialize
tcp_rsk(req)->req_usec_ts there instead of later in send_synack();

This means tcp_rsk(req)->req_usec_ts can be a boolean.

Many thanks to David an Neal for their help.

Fixes: 614e8316aa ("tcp: add support for usec resolution in TCP TS values")
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202310302216.f79d78bc-oliver.sang@intel.com
Suggested-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: David Morley <morleyd@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2023-10-31 06:19:45 +00:00 committed by David S. Miller
parent 63e201916b
commit cdbab62366
4 changed files with 6 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/tcp.h
View File

@ -152,7 +152,7 @@ struct tcp_request_sock {
u64 snt_synack; /* first SYNACK sent time */
bool tfo_listener;
bool is_mptcp;
s8 req_usec_ts;
bool req_usec_ts;
#if IS_ENABLED(CONFIG_MPTCP)
bool drop_req;
#endif

2
net/ipv4/syncookies.c
View File

@ -306,7 +306,7 @@ struct request_sock *cookie_tcp_reqsk_alloc(const struct request_sock_ops *ops,
treq->af_specific = af_ops;
treq->syn_tos = TCP_SKB_CB(skb)->ip_dsfield;
treq->req_usec_ts = -1;
treq->req_usec_ts = false;
#if IS_ENABLED(CONFIG_MPTCP)
treq->is_mptcp = sk_is_mptcp(sk);

7
net/ipv4/tcp_input.c
View File

@ -7115,7 +7115,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
req->syncookie = want_cookie;
tcp_rsk(req)->af_specific = af_ops;
tcp_rsk(req)->ts_off = 0;
tcp_rsk(req)->req_usec_ts = -1;
tcp_rsk(req)->req_usec_ts = false;
#if IS_ENABLED(CONFIG_MPTCP)
tcp_rsk(req)->is_mptcp = 0;
#endif
@ -7143,9 +7143,10 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
if (!dst)
goto drop_and_free;
if (tmp_opt.tstamp_ok)
if (tmp_opt.tstamp_ok) {
tcp_rsk(req)->req_usec_ts = dst_tcp_usec_ts(dst);
tcp_rsk(req)->ts_off = af_ops->init_ts_off(net, skb);
}
if (!want_cookie && !isn) {
int max_syn_backlog = READ_ONCE(net->ipv4.sysctl_max_syn_backlog);

2
net/ipv4/tcp_output.c
View File

@ -3693,8 +3693,6 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
mss = tcp_mss_clamp(tp, dst_metric_advmss(dst));
memset(&opts, 0, sizeof(opts));
if (tcp_rsk(req)->req_usec_ts < 0)
tcp_rsk(req)->req_usec_ts = dst_tcp_usec_ts(dst);
now = tcp_clock_ns();
#ifdef CONFIG_SYN_COOKIES
if (unlikely(synack_type == TCP_SYNACK_COOKIE && ireq->tstamp_ok))