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, 143 deletions

diff --git a/net/ipv4/tcp_metrics.c b/net/ipv4/tcp_metrics.c
index 0f46e5fe31ad..9d0d4f39e42b 100644
--- a/net/ipv4/tcp_metrics.c
+++ b/net/ipv4/tcp_metrics.c
@@ -45,8 +45,6 @@ struct tcp_metrics_block {
         struct inetpeer_addr            tcpm_saddr;
         struct inetpeer_addr            tcpm_daddr;
         unsigned long                   tcpm_stamp;
-        u32                             tcpm_ts;
-        u32                             tcpm_ts_stamp;
         u32                             tcpm_lock;
         u32                             tcpm_vals[TCP_METRIC_MAX_KERNEL + 1];
         struct tcp_fastopen_metrics     tcpm_fastopen;
@@ -123,8 +121,6 @@ static void tcpm_suck_dst(struct tcp_metrics_block *tm,
         tm->tcpm_vals[TCP_METRIC_SSTHRESH] = dst_metric_raw(dst, RTAX_SSTHRESH);
         tm->tcpm_vals[TCP_METRIC_CWND] = dst_metric_raw(dst, RTAX_CWND);
         tm->tcpm_vals[TCP_METRIC_REORDERING] = dst_metric_raw(dst, RTAX_REORDERING);
-        tm->tcpm_ts = 0;
-        tm->tcpm_ts_stamp = 0;
         if (fastopen_clear) {
                 tm->tcpm_fastopen.mss = 0;
                 tm->tcpm_fastopen.syn_loss = 0;
@@ -273,48 +269,6 @@ static struct tcp_metrics_block *__tcp_get_metrics_req(struct request_sock *req,
         return tm;
 }
 
-static struct tcp_metrics_block *__tcp_get_metrics_tw(struct inet_timewait_sock *tw)
-{
-        struct tcp_metrics_block *tm;
-        struct inetpeer_addr saddr, daddr;
-        unsigned int hash;
-        struct net *net;
-
-        if (tw->tw_family == AF_INET) {
-                inetpeer_set_addr_v4(&saddr, tw->tw_rcv_saddr);
-                inetpeer_set_addr_v4(&daddr, tw->tw_daddr);
-                hash = ipv4_addr_hash(tw->tw_daddr);
-        }
-#if IS_ENABLED(CONFIG_IPV6)
-        else if (tw->tw_family == AF_INET6) {
-                if (ipv6_addr_v4mapped(&tw->tw_v6_daddr)) {
-                        inetpeer_set_addr_v4(&saddr, tw->tw_rcv_saddr);
-                        inetpeer_set_addr_v4(&daddr, tw->tw_daddr);
-                        hash = ipv4_addr_hash(tw->tw_daddr);
-                } else {
-                        inetpeer_set_addr_v6(&saddr, &tw->tw_v6_rcv_saddr);
-                        inetpeer_set_addr_v6(&daddr, &tw->tw_v6_daddr);
-                        hash = ipv6_addr_hash(&tw->tw_v6_daddr);
-                }
-        }
-#endif
-        else
-                return NULL;
-
-        net = twsk_net(tw);
-        hash ^= net_hash_mix(net);
-        hash = hash_32(hash, tcp_metrics_hash_log);
-
-        for (tm = rcu_dereference(tcp_metrics_hash[hash].chain); tm;
-             tm = rcu_dereference(tm->tcpm_next)) {
-                if (addr_same(&tm->tcpm_saddr, &saddr) &&
-                    addr_same(&tm->tcpm_daddr, &daddr) &&
-                    net_eq(tm_net(tm), net))
-                        break;
-        }
-        return tm;
-}
-
 static struct tcp_metrics_block *tcp_get_metrics(struct sock *sk,
                                                  struct dst_entry *dst,
                                                  bool create)
@@ -573,8 +527,7 @@ reset:
         tp->snd_cwnd_stamp = tcp_time_stamp;
 }
 
-bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst,
-                        bool paws_check, bool timestamps)
+bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst)
 {
         struct tcp_metrics_block *tm;
         bool ret;
@@ -584,94 +537,10 @@ bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst,
 
         rcu_read_lock();
         tm = __tcp_get_metrics_req(req, dst);
-        if (paws_check) {
-                if (tm &&
-                    (u32)get_seconds() - tm->tcpm_ts_stamp < TCP_PAWS_MSL &&
-                    ((s32)(tm->tcpm_ts - req->ts_recent) > TCP_PAWS_WINDOW ||
-                     !timestamps))
-                        ret = false;
-                else
-                        ret = true;
-        } else {
-                if (tm && tcp_metric_get(tm, TCP_METRIC_RTT) && tm->tcpm_ts_stamp)
-                        ret = true;
-                else
-                        ret = false;
-        }
-        rcu_read_unlock();
-
-        return ret;
-}
-
-void tcp_fetch_timewait_stamp(struct sock *sk, struct dst_entry *dst)
-{
-        struct tcp_metrics_block *tm;
-
-        rcu_read_lock();
-        tm = tcp_get_metrics(sk, dst, true);
-        if (tm) {
-                struct tcp_sock *tp = tcp_sk(sk);
-
-                if ((u32)get_seconds() - tm->tcpm_ts_stamp <= TCP_PAWS_MSL) {
-                        tp->rx_opt.ts_recent_stamp = tm->tcpm_ts_stamp;
-                        tp->rx_opt.ts_recent = tm->tcpm_ts;
-                }
-        }
-        rcu_read_unlock();
-}
-EXPORT_SYMBOL_GPL(tcp_fetch_timewait_stamp);
-
-/* VJ's idea. Save last timestamp seen from this destination and hold
- * it at least for normal timewait interval to use for duplicate
- * segment detection in subsequent connections, before they enter
- * synchronized state.
- */
-bool tcp_remember_stamp(struct sock *sk)
-{
-        struct dst_entry *dst = __sk_dst_get(sk);
-        bool ret = false;
-
-        if (dst) {
-                struct tcp_metrics_block *tm;
-
-                rcu_read_lock();
-                tm = tcp_get_metrics(sk, dst, true);
-                if (tm) {
-                        struct tcp_sock *tp = tcp_sk(sk);
-
-                        if ((s32)(tm->tcpm_ts - tp->rx_opt.ts_recent) <= 0 ||
-                            ((u32)get_seconds() - tm->tcpm_ts_stamp > TCP_PAWS_MSL &&
-                             tm->tcpm_ts_stamp <= (u32)tp->rx_opt.ts_recent_stamp)) {
-                                tm->tcpm_ts_stamp = (u32)tp->rx_opt.ts_recent_stamp;
-                                tm->tcpm_ts = tp->rx_opt.ts_recent;
-                        }
-                        ret = true;
-                }
-                rcu_read_unlock();
-        }
-        return ret;
-}
-
-bool tcp_tw_remember_stamp(struct inet_timewait_sock *tw)
-{
-        struct tcp_metrics_block *tm;
-        bool ret = false;
-
-        rcu_read_lock();
-        tm = __tcp_get_metrics_tw(tw);
-        if (tm) {
-                const struct tcp_timewait_sock *tcptw;
-                struct sock *sk = (struct sock *) tw;
-
-                tcptw = tcp_twsk(sk);
-                if ((s32)(tm->tcpm_ts - tcptw->tw_ts_recent) <= 0 ||
-                    ((u32)get_seconds() - tm->tcpm_ts_stamp > TCP_PAWS_MSL &&
-                     tm->tcpm_ts_stamp <= (u32)tcptw->tw_ts_recent_stamp)) {
-                        tm->tcpm_ts_stamp = (u32)tcptw->tw_ts_recent_stamp;
-                        tm->tcpm_ts        = tcptw->tw_ts_recent;
-                }
+        if (tm && tcp_metric_get(tm, TCP_METRIC_RTT))
                 ret = true;
-        }
+        else
+                ret = false;
         rcu_read_unlock();
 
         return ret;
@@ -791,14 +660,6 @@ static int tcp_metrics_fill_info(struct sk_buff *msg,
                           jiffies - tm->tcpm_stamp,
                           TCP_METRICS_ATTR_PAD) < 0)
                 goto nla_put_failure;
-        if (tm->tcpm_ts_stamp) {
-                if (nla_put_s32(msg, TCP_METRICS_ATTR_TW_TS_STAMP,
-                                (s32) (get_seconds() - tm->tcpm_ts_stamp)) < 0)
-                        goto nla_put_failure;
-                if (nla_put_u32(msg, TCP_METRICS_ATTR_TW_TSVAL,
-                                tm->tcpm_ts) < 0)
-                        goto nla_put_failure;
-        }
 
         {
                 int n = 0;