Patch "tcp: restore fastopen with no data in SYN packet" has been added to the 4.3-stable tree

This is a note to let you know that I've just added the patch titled

tcp: restore fastopen with no data in SYN packet

to the 4.3-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
tcp-restore-fastopen-with-no-data-in-syn-packet.patch
and it can be found in the queue-4.3 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Eric Dumazet <[email protected]>
Date: Wed, 16 Dec 2015 13:53:10 -0800
Subject: tcp: restore fastopen with no data in SYN packet

From: Eric Dumazet <[email protected]>

[ Upstream commit 07e100f984975cb0417a7d5e626d0409efbad478 ]

Yuchung tracked a regression caused by commit 57be5bdad759 ("ip: convert tcp_sendmsg() to iov_iter primitives") for TCP Fast Open.

Some Fast Open users do not actually add any data in the SYN packet.

---
 net/ipv4/tcp_output.c |   23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

@@ -3147,7 +3147,7 @@ static int tcp_send_syn_data(struct sock
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct tcp_fastopen_request *fo = tp->fastopen_req;
-	int syn_loss = 0, space, err = 0, copied;
+	int syn_loss = 0, space, err = 0;
 	unsigned long last_syn_loss = 0;
 	struct sk_buff *syn_data;
 

@@ -3185,17 +3185,18 @@ static int tcp_send_syn_data(struct sock
 		goto fallback;
 	syn_data->ip_summed = CHECKSUM_PARTIAL;
 	memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));
-	copied = copy_from_iter(skb_put(syn_data, space), space,
-				&fo->data->msg_iter);
-	if (unlikely(!copied)) {
-		kfree_skb(syn_data);
-		goto fallback;
-	}
-	if (copied != space) {
-		skb_trim(syn_data, copied);
-		space = copied;
+	if (space) {
+		int copied = copy_from_iter(skb_put(syn_data, space), space,
+					    &fo->data->msg_iter);
+		if (unlikely(!copied)) {
+			kfree_skb(syn_data);
+			goto fallback;
+		}
+		if (copied != space) {
+			skb_trim(syn_data, copied);
+			space = copied;
+		}
 	}
-
 	/* No more data pending in inet_wait_for_connect() */
 	if (space == fo->size)
 		fo->data = NULL;

Patches currently in stable-queue which might be from [email protected] are

queue-4.3/inet-tcp-fix-inetpeer_set_addr_v4.patch queue-4.3/ipv6-sctp-clone-options-to-avoid-use-after-free.patch queue-4.3/tcp-restore-fastopen-with-no-data-in-syn-packet.patch queue-4.3/net_sched-make-qdisc_tree_decrease_qlen-work-for-non-mq.patch queue-4.3/net-fix-ip-early-demux-races.patch