tcp: remove tcp_tw_recycle

The tcp_tw_recycle was already broken for connections
behind NAT, since the per-destination timestamp is not
monotonically increasing for multiple machines behind
a single destination address.

After the randomization of TCP timestamp offsets
in commit 8a5bd45f6616 (tcp: randomize tcp timestamp offsets
for each connection), the tcp_tw_recycle is broken for all
types of connections for the same reason: the timestamps
received from a single machine is not monotonically increasing,
anymore.

Remove tcp_tw_recycle, since it is not functional. Also, remove
the PAWSPassive SNMP counter since it is only used for
tcp_tw_recycle, and simplify tcp_v4_route_req and tcp_v6_route_req
since the strict argument is only set when tcp_tw_recycle is
enabled.

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/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index ab02304..ed3d079 100644 (file)
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -640,11 +640,6 @@ tcp_tso_win_divisor - INTEGER
        building larger TSO frames.
        Default: 3
 
-tcp_tw_recycle - BOOLEAN
-       Enable fast recycling TIME-WAIT sockets. Default value is 0.
-       It should not be changed without advice/request of technical
-       experts.
-
 tcp_tw_reuse - BOOLEAN
        Allow to reuse TIME-WAIT sockets for new connections when it is
        safe from protocol viewpoint. Default value is 0.

diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h
index 622d2da..2e9d649 100644 (file)
--- a/include/net/netns/ipv4.h
+++ b/include/net/netns/ipv4.h
@@ -33,7 +33,6 @@ struct inet_timewait_death_row {
        atomic_t                tw_count;
 
        struct inet_hashinfo    *hashinfo ____cacheline_aligned_in_smp;
-       int                     sysctl_tw_recycle;
        int                     sysctl_max_tw_buckets;
 };
 

diff --git a/include/net/tcp.h b/include/net/tcp.h
index c81f3b9..e614ad4 100644 (file)
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1810,8 +1810,7 @@ struct tcp_request_sock_ops {
                                 __u16 *mss);
 #endif
        struct dst_entry *(*route_req)(const struct sock *sk, struct flowi *fl,
-                                      const struct request_sock *req,
-                                      bool *strict);
+                                      const struct request_sock *req);
        __u32 (*init_seq_tsoff)(const struct sk_buff *skb, u32 *tsoff);
        int (*send_synack)(const struct sock *sk, struct dst_entry *dst,
                           struct flowi *fl, struct request_sock *req,

diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h
index 3b2bed7..cec0e17 100644 (file)
--- a/include/uapi/linux/snmp.h
+++ b/include/uapi/linux/snmp.h
@@ -177,7 +177,6 @@ enum
        LINUX_MIB_TIMEWAITED,                   /* TimeWaited */
        LINUX_MIB_TIMEWAITRECYCLED,             /* TimeWaitRecycled */
        LINUX_MIB_TIMEWAITKILLED,               /* TimeWaitKilled */
-       LINUX_MIB_PAWSPASSIVEREJECTED,          /* PAWSPassiveRejected */
        LINUX_MIB_PAWSACTIVEREJECTED,           /* PAWSActiveRejected */
        LINUX_MIB_PAWSESTABREJECTED,            /* PAWSEstabRejected */
        LINUX_MIB_DELAYEDACKS,                  /* DelayedACKs */

diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index 69cf49e..4ccbf46 100644 (file)
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -199,7 +199,6 @@ static const struct snmp_mib snmp4_net_list[] = {
        SNMP_MIB_ITEM("TW", LINUX_MIB_TIMEWAITED),
        SNMP_MIB_ITEM("TWRecycled", LINUX_MIB_TIMEWAITRECYCLED),
        SNMP_MIB_ITEM("TWKilled", LINUX_MIB_TIMEWAITKILLED),
-       SNMP_MIB_ITEM("PAWSPassive", LINUX_MIB_PAWSPASSIVEREJECTED),
        SNMP_MIB_ITEM("PAWSActive", LINUX_MIB_PAWSACTIVEREJECTED),
        SNMP_MIB_ITEM("PAWSEstab", LINUX_MIB_PAWSESTABREJECTED),
        SNMP_MIB_ITEM("DelayedACKs", LINUX_MIB_DELAYEDACKS),

diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index d6880a6..11aaef0 100644 (file)
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -981,13 +981,6 @@ static struct ctl_table ipv4_net_table[] = {
                .proc_handler   = proc_dointvec
        },
        {
-               .procname       = "tcp_tw_recycle",
-               .data           = &init_net.ipv4.tcp_death_row.sysctl_tw_recycle,
-               .maxlen         = sizeof(int),
-               .mode           = 0644,
-               .proc_handler   = proc_dointvec
-       },
-       {
                .procname       = "tcp_max_syn_backlog",
                .data           = &init_net.ipv4.sysctl_max_syn_backlog,
                .maxlen         = sizeof(int),

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index aafec06..bb09c70 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6327,31 +6327,11 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
                af_ops->init_seq_tsoff(skb, &tcp_rsk(req)->ts_off);
 
        if (!want_cookie && !isn) {
-               /* VJ's idea. We save last timestamp seen
-                * from the destination in peer table, when entering
-                * state TIME-WAIT, and check against it before
-                * accepting new connection request.
-                *
-                * If "isn" is not zero, this request hit alive
-                * timewait bucket, so that all the necessary checks
-                * are made in the function processing timewait state.
-                */
-               if (net->ipv4.tcp_death_row.sysctl_tw_recycle) {
-                       bool strict;
-
-                       dst = af_ops->route_req(sk, &fl, req, &strict);
-
-                       if (dst && strict &&
-                           !tcp_peer_is_proven(req, dst)) {
-                               NET_INC_STATS(sock_net(sk), LINUX_MIB_PAWSPASSIVEREJECTED);
-                               goto drop_and_release;
-                       }
-               }
                /* Kill the following clause, if you dislike this way. */
-               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)) {
+               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)) {
                        /* Without syncookies last quarter of
                         * backlog is filled with destinations,
                         * proven to be alive.
@@ -6367,7 +6347,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
                isn = af_ops->init_seq_tsoff(skb, &tcp_rsk(req)->ts_off);
        }
        if (!dst) {
-               dst = af_ops->route_req(sk, &fl, req, NULL);
+               dst = af_ops->route_req(sk, &fl, req);
                if (!dst)
                        goto drop_and_free;
        }

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index d8b401f..7482b5d 100644 (file)
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1213,19 +1213,9 @@ static void tcp_v4_init_req(struct request_sock *req,
 
 static struct dst_entry *tcp_v4_route_req(const struct sock *sk,
                                          struct flowi *fl,
-                                         const struct request_sock *req,
-                                         bool *strict)
+                                         const struct request_sock *req)
 {
-       struct dst_entry *dst = inet_csk_route_req(sk, &fl->u.ip4, req);
-
-       if (strict) {
-               if (fl->u.ip4.daddr == inet_rsk(req)->ir_rmt_addr)
-                       *strict = true;
-               else
-                       *strict = false;
-       }
-
-       return dst;
+       return inet_csk_route_req(sk, &fl->u.ip4, req);
 }
 
 struct request_sock_ops tcp_request_sock_ops __read_mostly = {
@@ -2462,7 +2452,6 @@ static int __net_init tcp_sk_init(struct net *net)
        net->ipv4.sysctl_tcp_tw_reuse = 0;
 
        cnt = tcp_hashinfo.ehash_mask + 1;
-       net->ipv4.tcp_death_row.sysctl_tw_recycle = 0;
        net->ipv4.tcp_death_row.sysctl_max_tw_buckets = (cnt + 1) / 2;
        net->ipv4.tcp_death_row.hashinfo = &tcp_hashinfo;
 

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 853cb43..0f08d71 100644 (file)
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -722,11 +722,8 @@ static void tcp_v6_init_req(struct request_sock *req,
 
 static struct dst_entry *tcp_v6_route_req(const struct sock *sk,
                                          struct flowi *fl,
-                                         const struct request_sock *req,
-                                         bool *strict)
+                                         const struct request_sock *req)
 {
-       if (strict)
-               *strict = true;
        return inet6_csk_route_req(sk, &fl->u.ip6, req, IPPROTO_TCP);
 }