tcp: Add stats for socket migration.

This commit adds two stats for the socket migration feature to evaluate the
effectiveness: LINUX_MIB_TCPMIGRATEREQ(SUCCESS|FAILURE).

If the migration fails because of the own_req race in receiving ACK and
sending SYN+ACK paths, we do not increment the failure stat. Then another
CPU is responsible for the req.

Link: https://lore.kernel.org/bpf/CAK6E8=cgFKuGecTzSCSQ8z3YJ_163C0uwO9yRvfDSE7vOe9mJA@mail.gmail.com/
Suggested-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
Acked-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h
index 26fc60c..904909d 100644 (file)
--- a/include/uapi/linux/snmp.h
+++ b/include/uapi/linux/snmp.h
@@ -290,6 +290,8 @@ enum
        LINUX_MIB_TCPDUPLICATEDATAREHASH,       /* TCPDuplicateDataRehash */
        LINUX_MIB_TCPDSACKRECVSEGS,             /* TCPDSACKRecvSegs */
        LINUX_MIB_TCPDSACKIGNOREDDUBIOUS,       /* TCPDSACKIgnoredDubious */
+       LINUX_MIB_TCPMIGRATEREQSUCCESS,         /* TCPMigrateReqSuccess */
+       LINUX_MIB_TCPMIGRATEREQFAILURE,         /* TCPMigrateReqFailure */
        __LINUX_MIB_MAX
 };
 

diff --git a/net/core/sock_reuseport.c b/net/core/sock_reuseport.c
index de5ee3a..3f00a28 100644 (file)
--- a/net/core/sock_reuseport.c
+++ b/net/core/sock_reuseport.c
@@ -6,6 +6,7 @@
  * selecting the socket index from the array of available sockets.
  */
 
+#include <net/ip.h>
 #include <net/sock_reuseport.h>
 #include <linux/bpf.h>
 #include <linux/idr.h>
@@ -536,7 +537,7 @@ struct sock *reuseport_migrate_sock(struct sock *sk,
 
        socks = READ_ONCE(reuse->num_socks);
        if (unlikely(!socks))
-               goto out;
+               goto failure;
 
        /* paired with smp_wmb() in __reuseport_add_sock() */
        smp_rmb();
@@ -546,13 +547,13 @@ struct sock *reuseport_migrate_sock(struct sock *sk,
        if (!prog || prog->expected_attach_type != BPF_SK_REUSEPORT_SELECT_OR_MIGRATE) {
                if (sock_net(sk)->ipv4.sysctl_tcp_migrate_req)
                        goto select_by_hash;
-               goto out;
+               goto failure;
        }
 
        if (!skb) {
                skb = alloc_skb(0, GFP_ATOMIC);
                if (!skb)
-                       goto out;
+                       goto failure;
                allocated = true;
        }
 
@@ -565,12 +566,18 @@ select_by_hash:
        if (!nsk)
                nsk = reuseport_select_sock_by_hash(reuse, hash, socks);
 
-       if (IS_ERR_OR_NULL(nsk) || unlikely(!refcount_inc_not_zero(&nsk->sk_refcnt)))
+       if (IS_ERR_OR_NULL(nsk) || unlikely(!refcount_inc_not_zero(&nsk->sk_refcnt))) {
                nsk = NULL;
+               goto failure;
+       }
 
 out:
        rcu_read_unlock();
        return nsk;
+
+failure:
+       __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMIGRATEREQFAILURE);
+       goto out;
 }
 EXPORT_SYMBOL(reuseport_migrate_sock);
 

diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 0eea878..754013f 100644 (file)
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -703,6 +703,8 @@ static struct request_sock *inet_reqsk_clone(struct request_sock *req,
 
        nreq = kmem_cache_alloc(req->rsk_ops->slab, GFP_ATOMIC | __GFP_NOWARN);
        if (!nreq) {
+               __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMIGRATEREQFAILURE);
+
                /* paired with refcount_inc_not_zero() in reuseport_migrate_sock() */
                sock_put(sk);
                return NULL;
@@ -876,9 +878,10 @@ static void reqsk_timer_handler(struct timer_list *t)
                if (!inet_ehash_insert(req_to_sk(nreq), req_to_sk(oreq), NULL)) {
                        /* delete timer */
                        inet_csk_reqsk_queue_drop(sk_listener, nreq);
-                       goto drop;
+                       goto no_ownership;
                }
 
+               __NET_INC_STATS(net, LINUX_MIB_TCPMIGRATEREQSUCCESS);
                reqsk_migrate_reset(oreq);
                reqsk_queue_removed(&inet_csk(oreq->rsk_listener)->icsk_accept_queue, oreq);
                reqsk_put(oreq);
@@ -887,17 +890,19 @@ static void reqsk_timer_handler(struct timer_list *t)
                return;
        }
 
-drop:
        /* Even if we can clone the req, we may need not retransmit any more
         * SYN+ACKs (nreq->num_timeout > max_syn_ack_retries, etc), or another
         * CPU may win the "own_req" race so that inet_ehash_insert() fails.
         */
        if (nreq) {
+               __NET_INC_STATS(net, LINUX_MIB_TCPMIGRATEREQFAILURE);
+no_ownership:
                reqsk_migrate_reset(nreq);
                reqsk_queue_removed(queue, nreq);
                __reqsk_free(nreq);
        }
 
+drop:
        inet_csk_reqsk_queue_drop_and_put(oreq->rsk_listener, oreq);
 }
 
@@ -1135,11 +1140,13 @@ struct sock *inet_csk_complete_hashdance(struct sock *sk, struct sock *child,
 
                        refcount_set(&nreq->rsk_refcnt, 1);
                        if (inet_csk_reqsk_queue_add(sk, nreq, child)) {
+                               __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMIGRATEREQSUCCESS);
                                reqsk_migrate_reset(req);
                                reqsk_put(req);
                                return child;
                        }
 
+                       __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMIGRATEREQFAILURE);
                        reqsk_migrate_reset(nreq);
                        __reqsk_free(nreq);
                } else if (inet_csk_reqsk_queue_add(sk, req, child)) {
@@ -1188,8 +1195,12 @@ void inet_csk_listen_stop(struct sock *sk)
                                refcount_set(&nreq->rsk_refcnt, 1);
 
                                if (inet_csk_reqsk_queue_add(nsk, nreq, child)) {
+                                       __NET_INC_STATS(sock_net(nsk),
+                                                       LINUX_MIB_TCPMIGRATEREQSUCCESS);
                                        reqsk_migrate_reset(req);
                                } else {
+                                       __NET_INC_STATS(sock_net(nsk),
+                                                       LINUX_MIB_TCPMIGRATEREQFAILURE);
                                        reqsk_migrate_reset(nreq);
                                        __reqsk_free(nreq);
                                }

diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index 6d46297..b0d3a09 100644 (file)
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -295,6 +295,8 @@ static const struct snmp_mib snmp4_net_list[] = {
        SNMP_MIB_ITEM("TcpDuplicateDataRehash", LINUX_MIB_TCPDUPLICATEDATAREHASH),
        SNMP_MIB_ITEM("TCPDSACKRecvSegs", LINUX_MIB_TCPDSACKRECVSEGS),
        SNMP_MIB_ITEM("TCPDSACKIgnoredDubious", LINUX_MIB_TCPDSACKIGNOREDDUBIOUS),
+       SNMP_MIB_ITEM("TCPMigrateReqSuccess", LINUX_MIB_TCPMIGRATEREQSUCCESS),
+       SNMP_MIB_ITEM("TCPMigrateReqFailure", LINUX_MIB_TCPMIGRATEREQFAILURE),
        SNMP_MIB_SENTINEL
 };
 

diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index f258a4c..0a4f3f1 100644 (file)
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -786,6 +786,9 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
        return inet_csk_complete_hashdance(sk, child, req, own_req);
 
 listen_overflow:
+       if (sk != req->rsk_listener)
+               __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMIGRATEREQFAILURE);
+
        if (!sock_net(sk)->ipv4.sysctl_tcp_abort_on_overflow) {
                inet_rsk(req)->acked = 1;
                return NULL;