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tcp/dccp: fix behavior of stale SYN_RECV request sockets

Browse source 
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: 079096f103 ("tcp/dccp: install syn_recv requests into ehash table")
Signed-off-by: Eric Dumazet <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
This commit is contained in:
Eric Dumazet 2015-10-13 17:12:54 -07:00 • committed by David S. Miller
commit 4bdc3d6614
4 changed files with 26 additions and 18 deletions
Download patch file Download diff file Expand all files Collapse all files

15
net/dccp/ipv4.c
View file

@ -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;

15
net/dccp/ipv6.c
View file

@ -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;