tcp/dccp: fix behavior of stale SYN_RECV request sockets

When a TCP/DCCP listener is closed, its pending SYN_RECV request sockets
become stale, meaning 3WHS can not complete.

But current behavior is wrong :
incoming packets finding such stale sockets are dropped.

We need instead to cleanup the request socket and perform another
lookup :
- Incoming ACK will give a RST answer,
- SYN rtx might find another listener if available.
- We expedite cleanup of request sockets and old listener socket.

Fixes: 079096f103fa ("tcp/dccp: install syn_recv requests into ehash table")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index 8e99681..0dcf196 100644 (file)
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -799,15 +799,10 @@ static int dccp_v4_rcv(struct sk_buff *skb)
                                  DCCP_SKB_CB(skb)->dccpd_ack_seq);
        }
 
-       /* Step 2:
-        *      Look up flow ID in table and get corresponding socket */
+lookup:
        sk = __inet_lookup_skb(&dccp_hashinfo, skb,
                               dh->dccph_sport, dh->dccph_dport);
-       /*
-        * Step 2:
-        *      If no socket ...
-        */
-       if (sk == NULL) {
+       if (!sk) {
                dccp_pr_debug("failed to look up flow ID in table and "
                              "get corresponding socket\n");
                goto no_dccp_socket;
@@ -830,8 +825,12 @@ static int dccp_v4_rcv(struct sk_buff *skb)
                struct sock *nsk = NULL;
 
                sk = req->rsk_listener;
-               if (sk->sk_state == DCCP_LISTEN)
+               if (likely(sk->sk_state == DCCP_LISTEN)) {
                        nsk = dccp_check_req(sk, skb, req);
+               } else {
+                       inet_csk_reqsk_queue_drop(sk, req);
+                       goto lookup;
+               }
                if (!nsk) {
                        reqsk_put(req);
                        goto discard_it;

diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c
index aed314f..6883193 100644 (file)
--- a/net/dccp/ipv6.c
+++ b/net/dccp/ipv6.c
@@ -656,16 +656,11 @@ static int dccp_v6_rcv(struct sk_buff *skb)
        else
                DCCP_SKB_CB(skb)->dccpd_ack_seq = dccp_hdr_ack_seq(skb);
 
-       /* Step 2:
-        *      Look up flow ID in table and get corresponding socket */
+lookup:
        sk = __inet6_lookup_skb(&dccp_hashinfo, skb,
                                dh->dccph_sport, dh->dccph_dport,
                                inet6_iif(skb));
-       /*
-        * Step 2:
-        *      If no socket ...
-        */
-       if (sk == NULL) {
+       if (!sk) {
                dccp_pr_debug("failed to look up flow ID in table and "
                              "get corresponding socket\n");
                goto no_dccp_socket;
@@ -688,8 +683,12 @@ static int dccp_v6_rcv(struct sk_buff *skb)
                struct sock *nsk = NULL;
 
                sk = req->rsk_listener;
-               if (sk->sk_state == DCCP_LISTEN)
+               if (likely(sk->sk_state == DCCP_LISTEN)) {
                        nsk = dccp_check_req(sk, skb, req);
+               } else {
+                       inet_csk_reqsk_queue_drop(sk, req);
+                       goto lookup;
+               }
                if (!nsk) {
                        reqsk_put(req);
                        goto discard_it;

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index ddb1983..1ff0923 100644 (file)
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1572,6 +1572,7 @@ int tcp_v4_rcv(struct sk_buff *skb)
        TCP_SKB_CB(skb)->ip_dsfield = ipv4_get_dsfield(iph);
        TCP_SKB_CB(skb)->sacked  = 0;
 
+lookup:
        sk = __inet_lookup_skb(&tcp_hashinfo, skb, th->source, th->dest);
        if (!sk)
                goto no_tcp_socket;
@@ -1587,8 +1588,12 @@ process:
                sk = req->rsk_listener;
                if (tcp_v4_inbound_md5_hash(sk, skb))
                        goto discard_and_relse;
-               if (sk->sk_state == TCP_LISTEN)
+               if (likely(sk->sk_state == TCP_LISTEN)) {
                        nsk = tcp_check_req(sk, skb, req, false);
+               } else {
+                       inet_csk_reqsk_queue_drop(sk, req);
+                       goto lookup;
+               }
                if (!nsk) {
                        reqsk_put(req);
                        goto discard_it;

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 2887c84..7ce1c57 100644 (file)
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1363,6 +1363,7 @@ static int tcp_v6_rcv(struct sk_buff *skb)
        th = tcp_hdr(skb);
        hdr = ipv6_hdr(skb);
 
+lookup:
        sk = __inet6_lookup_skb(&tcp_hashinfo, skb, th->source, th->dest,
                                inet6_iif(skb));
        if (!sk)
@@ -1382,8 +1383,12 @@ process:
                        reqsk_put(req);
                        goto discard_it;
                }
-               if (sk->sk_state == TCP_LISTEN)
+               if (likely(sk->sk_state == TCP_LISTEN)) {
                        nsk = tcp_check_req(sk, skb, req, false);
+               } else {
+                       inet_csk_reqsk_queue_drop(sk, req);
+                       goto lookup;
+               }
                if (!nsk) {
                        reqsk_put(req);
                        goto discard_it;