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>

diff --git a/include/net/tcp.h b/include/net/tcp.h
index bede8f7fa7426bb6ab04e7590b63bee04ffac0ed..c81f3b958d44f1cece510426b590be7af33d9b65 100644 (file)
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -406,11 +406,7 @@ void tcp_clear_retrans(struct tcp_sock *tp);
 void tcp_update_metrics(struct sock *sk);
 void tcp_init_metrics(struct sock *sk);
 void tcp_metrics_init(void);
-bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst,
-                       bool paws_check, bool timestamps);
-bool tcp_remember_stamp(struct sock *sk);
-bool tcp_tw_remember_stamp(struct inet_timewait_sock *tw);
-void tcp_fetch_timewait_stamp(struct sock *sk, struct dst_entry *dst);
+bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst);
 void tcp_disable_fack(struct tcp_sock *tp);
 void tcp_close(struct sock *sk, long timeout);
 void tcp_init_sock(struct sock *sk);

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 96b67a8b18c3c389df115ab8764c30a5e3924533..aafec0676d3eda85af575c1771eb2fdea61f3146 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6342,8 +6342,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
                        dst = af_ops->route_req(sk, &fl, req, &strict);
 
                        if (dst && strict &&
-                           !tcp_peer_is_proven(req, dst, true,
-                                               tmp_opt.saw_tstamp)) {
+                           !tcp_peer_is_proven(req, dst)) {
                                NET_INC_STATS(sock_net(sk), LINUX_MIB_PAWSPASSIVEREJECTED);
                                goto drop_and_release;
                        }
@@ -6352,8 +6351,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
                else if (!net->ipv4.sysctl_tcp_syncookies &&
                         (net->ipv4.sysctl_max_syn_backlog - inet_csk_reqsk_queue_len(sk) <
                          (net->ipv4.sysctl_max_syn_backlog >> 2)) &&
-                        !tcp_peer_is_proven(req, dst, false,
-                                            tmp_opt.saw_tstamp)) {
+                        !tcp_peer_is_proven(req, dst)) {
                        /* Without syncookies last quarter of
                         * backlog is filled with destinations,
                         * proven to be alive.

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 08d870e45658f51e9c9c8f0047290c05e61c1bc4..d8b401fff9feb63f4357cfe31b0875ccead1f1c3 100644 (file)
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -198,10 +198,6 @@ int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
                        tp->write_seq      = 0;
        }
 
-       if (tcp_death_row->sysctl_tw_recycle &&
-           !tp->rx_opt.ts_recent_stamp && fl4->daddr == daddr)
-               tcp_fetch_timewait_stamp(sk, &rt->dst);
-
        inet->inet_dport = usin->sin_port;
        sk_daddr_set(sk, daddr);
 

diff --git a/net/ipv4/tcp_metrics.c b/net/ipv4/tcp_metrics.c
index 0f46e5fe31ad1b6809ada1f70bce7b63df4f8c9c..9d0d4f39e42be15d8ad7389bc7562449b92ea5fa 100644 (file)
--- 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;

diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 7e16243cdb58c830f869fe483730e86400e2eb00..692f974e5abefd6d798438c120adb393971cf262 100644 (file)
--- 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. */

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index c73a431fd06f90814d30e03d9c1307c4313dbd42..853cb43e3e3cabd63c22dd3ea25ffaabba03dbdf 100644 (file)
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -265,11 +265,6 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
        sk->sk_gso_type = SKB_GSO_TCPV6;
        ip6_dst_store(sk, dst, NULL, NULL);
 
-       if (tcp_death_row->sysctl_tw_recycle &&
-           !tp->rx_opt.ts_recent_stamp &&
-           ipv6_addr_equal(&fl6.daddr, &sk->sk_v6_daddr))
-               tcp_fetch_timewait_stamp(sk, dst);
-
        icsk->icsk_ext_hdr_len = 0;
        if (opt)
                icsk->icsk_ext_hdr_len = opt->opt_flen +