tcp: remove per-destination timestamp cache

Commit 8a5bd45f6616 (tcp: randomize tcp timestamp offsets for each connection)
randomizes TCP timestamps per connection. After this commit,
there is no guarantee that the timestamps received from the
same destination are monotonically increasing. As a result,
the per-destination timestamp cache in TCP metrics (i.e., tcpm_ts
in struct tcp_metrics_block) is broken and cannot be relied upon.

Remove the per-destination timestamp cache and all related code
paths.

Note that this cache was already broken for caching timestamps of
multiple machines behind a NAT sharing the same address.

Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Cc: Lutz Vieweg <lvml@5t9.de>
Cc: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 18 deletions

diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 7e16243cdb58..692f974e5abe 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -94,7 +94,6 @@ tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb,
         struct tcp_options_received tmp_opt;
         struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw);
         bool paws_reject = false;
-        struct inet_timewait_death_row *tcp_death_row = &sock_net((struct sock*)tw)->ipv4.tcp_death_row;
 
         tmp_opt.saw_tstamp = 0;
         if (th->doff > (sizeof(*th) >> 2) && tcptw->tw_ts_recent_stamp) {
@@ -149,12 +148,7 @@ tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb,
                         tcptw->tw_ts_recent       = tmp_opt.rcv_tsval;
                 }
 
-                if (tcp_death_row->sysctl_tw_recycle &&
-                    tcptw->tw_ts_recent_stamp &&
-                    tcp_tw_remember_stamp(tw))
-                        inet_twsk_reschedule(tw, tw->tw_timeout);
-                else
-                        inet_twsk_reschedule(tw, TCP_TIMEWAIT_LEN);
+                inet_twsk_reschedule(tw, TCP_TIMEWAIT_LEN);
                 return TCP_TW_ACK;
         }
 
@@ -259,12 +253,8 @@ void tcp_time_wait(struct sock *sk, int state, int timeo)
         const struct inet_connection_sock *icsk = inet_csk(sk);
         const struct tcp_sock *tp = tcp_sk(sk);
         struct inet_timewait_sock *tw;
-        bool recycle_ok = false;
         struct inet_timewait_death_row *tcp_death_row = &sock_net(sk)->ipv4.tcp_death_row;
 
-        if (tcp_death_row->sysctl_tw_recycle && tp->rx_opt.ts_recent_stamp)
-                recycle_ok = tcp_remember_stamp(sk);
-
         tw = inet_twsk_alloc(sk, tcp_death_row, state);
 
         if (tw) {
@@ -317,13 +307,9 @@ void tcp_time_wait(struct sock *sk, int state, int timeo)
                 if (timeo < rto)
                         timeo = rto;
 
-                if (recycle_ok) {
-                        tw->tw_timeout = rto;
-                } else {
-                        tw->tw_timeout = TCP_TIMEWAIT_LEN;
-                        if (state == TCP_TIME_WAIT)
-                                timeo = TCP_TIMEWAIT_LEN;
-                }
+                tw->tw_timeout = TCP_TIMEWAIT_LEN;
+                if (state == TCP_TIME_WAIT)
+                        timeo = TCP_TIMEWAIT_LEN;
 
                 inet_twsk_schedule(tw, timeo);
                 /* Linkage updates. */