[PATCH] tcp: fix regression in urgent data handling

From: Eric Dumazet <edumazet@google.com>

Stephan Springl found that commit 1402d366019fed "tcp: introduce
tcp_try_coalesce" introduced a regression for rlogin

It turns out problem comes from TCP urgent data handling and
a change in behavior in input path.

rlogin sends two one-byte packets with URG ptr set, and when next data
frame is coalesced, we lack sk_data_ready() calls to wakeup consumer.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Stephan Springl <redacted>
Cc: Alexander Duyck <redacted>
---
 net/ipv4/tcp_input.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 6e38c6c..d377f48 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c

@@ -4661,7 +4661,7 @@ queue_and_out:
 
 		if (eaten > 0)
 			kfree_skb_partial(skb, fragstolen);
-		else if (!sock_flag(sk, SOCK_DEAD))
+		if (!sock_flag(sk, SOCK_DEAD))
 			sk->sk_data_ready(sk, 0);
 		return;
 	}

@@ -5556,8 +5556,7 @@ no_ack:
 #endif
 			if (eaten)
 				kfree_skb_partial(skb, fragstolen);
-			else
-				sk->sk_data_ready(sk, 0);
+			sk->sk_data_ready(sk, 0);
 			return 0;
 		}
 	}

From: Eric Dumazet <edumazet@google.com>

Stephan Springl found that commit 1402d366019fed "tcp: introduce
tcp_try_coalesce" introduced a regression for rlogin

It turns out problem comes from TCP urgent data handling and
a change in behavior in input path.

rlogin sends two one-byte packets with URG ptr set, and when next data
frame is coalesced, we lack sk_data_ready() calls to wakeup consumer.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Stephan Springl <redacted>
Cc: Alexander Duyck <redacted>
---
v2: Changed Stephan Springl email address in changelog/CC

 net/ipv4/tcp_input.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 6e38c6c..d377f48 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c

@@ -4661,7 +4661,7 @@ queue_and_out:
 
 		if (eaten > 0)
 			kfree_skb_partial(skb, fragstolen);
-		else if (!sock_flag(sk, SOCK_DEAD))
+		if (!sock_flag(sk, SOCK_DEAD))
 			sk->sk_data_ready(sk, 0);
 		return;
 	}

@@ -5556,8 +5556,7 @@ no_ack:
 #endif
 			if (eaten)
 				kfree_skb_partial(skb, fragstolen);
-			else
-				sk->sk_data_ready(sk, 0);
+			sk->sk_data_ready(sk, 0);
 			return 0;
 		}
 	}

Works here on top of 3.5.4, so

Tested-by: Stephan Springl <redacted>

On Tue, 18 Sep 2012, Eric Dumazet wrote:

Freundliche Grüße

BFW Werner Völk GmbH
ppa. Stephan Springl
-- 
Stephan Springl                           BFW Werner Völk GmbH
Tel.:  +49 89 82917-452                   Energiemesstechnik & Service
Fax:   +49 89 82917-599                   Pasinger Str. 20 - 22
Mail:  springl@bfw-online.de              D-82166 Gräfelfing
Web:   http://www.novamess.de             Geschäftsführer: Georg F. Völk
                                           HRB 44779 Amtsgericht München
                                           USt.-ID: DE129301566

From: Eric Dumazet <redacted>
Date: Tue, 18 Sep 2012 00:51:39 +0200

From: Eric Dumazet <edumazet@google.com>

Stephan Springl found that commit 1402d366019fed "tcp: introduce
tcp_try_coalesce" introduced a regression for rlogin

It turns out problem comes from TCP urgent data handling and
a change in behavior in input path.

rlogin sends two one-byte packets with URG ptr set, and when next data
frame is coalesced, we lack sk_data_ready() calls to wakeup consumer.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Stephan Springl <redacted>
Cc: Alexander Duyck <redacted>

Applied, thanks Eric.