tcp: increment sk_drops for listeners

Goal: packets dropped by a listener are accounted for.

This adds tcp_listendrop() helper, and clears sk_drops in sk_clone_lock()
so that children do not inherit their parent drop count.

Note that we no longer increment LINUX_MIB_LISTENDROPS counter when
sending a SYNCOOKIE, since the SYN packet generated a SYNACK.
We already have a separate LINUX_MIB_SYNCOOKIESSENT

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 8 insertions, 6 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 0ffcd07e3409..983f04c11177 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6339,8 +6339,10 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
                         inet_csk_reqsk_queue_hash_add(sk, req, TCP_TIMEOUT_INIT);
                 af_ops->send_synack(sk, dst, &fl, req,
                                     &foc, !want_cookie);
-                if (want_cookie)
-                        goto drop_and_free;
+                if (want_cookie) {
+                        reqsk_free(req);
+                        return 0;
+                }
         }
         reqsk_put(req);
         return 0;
@@ -6350,7 +6352,7 @@ drop_and_release:
 drop_and_free:
         reqsk_free(req);
 drop:
-        NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENDROPS);
+        tcp_listendrop(sk);
         return 0;
 }
 EXPORT_SYMBOL(tcp_conn_request);
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 059a98f5e7e1..f3ce0afe70aa 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -329,7 +329,7 @@ void tcp_req_err(struct sock *sk, u32 seq, bool abort)
                  * errors returned from accept().
                  */
                 inet_csk_reqsk_queue_drop(req->rsk_listener, req);
-                NET_INC_STATS_BH(net, LINUX_MIB_LISTENDROPS);
+                tcp_listendrop(req->rsk_listener);
         }
         reqsk_put(req);
 }
@@ -1246,7 +1246,7 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
                                 &tcp_request_sock_ipv4_ops, sk, skb);
 
 drop:
-        NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENDROPS);
+        tcp_listendrop(sk);
         return 0;
 }
 EXPORT_SYMBOL(tcp_v4_conn_request);
@@ -1348,7 +1348,7 @@ exit_overflow:
 exit_nonewsk:
         dst_release(dst);
 exit:
-        NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENDROPS);
+        tcp_listendrop(sk);
         return NULL;
 put_and_exit:
         inet_csk_prepare_forced_close(newsk);