[PATCH 1/1] tcp: Honor the eor bit in tcp_mtu

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* [PATCH 1/1] tcp: Honor the eor bit in tcp_mtu_probe
@ 2018-02-05 15:11 Ilya Lesokhin
  2018-02-05 15:52 ` Eric Dumazet
  2018-02-06 21:29 ` kbuild test robot
  0 siblings, 2 replies; 4+ messages in thread
From: Ilya Lesokhin @ 2018-02-05 15:11 UTC (permalink / raw)
  To: netdev, kafai; +Cc: borisp, Ilya Lesokhin

Avoid SKB coalescing if eor bit is set in one of the relevant
SKBs.

Fixes: c134ecb87817 ("tcp: Make use of MSG_EOR in tcp_sendmsg")
Signed-off-by: Ilya Lesokhin <ilyal@mellanox.com>
---
 net/ipv4/tcp_output.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index e9f985e42405..c8cc679f1779 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2099,6 +2099,17 @@ static int tcp_mtu_probe(struct sock *sk)
 			return 0;
 	}
 
+	len = probe_size;
+	tcp_for_write_queue_from_safe(skb, next, sk) {
+		if (len <= skb->len)
+			break;
+
+		if (unlikely(TCP_SKB_CB(skb)->eor))
+			return -1;
+
+		len -= skb->len;
+	}
+
 	/* We're allowed to probe.  Build it now. */
 	nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC, false);
 	if (!nskb)
-- 
2.15.0.317.g14c63a9

^ permalink raw reply related	[flat|nested] 4+ messages in thread

* Re: [PATCH 1/1] tcp: Honor the eor bit in tcp_mtu_probe
  2018-02-05 15:11 [PATCH 1/1] tcp: Honor the eor bit in tcp_mtu_probe Ilya Lesokhin
@ 2018-02-05 15:52 ` Eric Dumazet
  2018-02-05 17:10   ` Eric Dumazet
  2018-02-06 21:29 ` kbuild test robot
  1 sibling, 1 reply; 4+ messages in thread
From: Eric Dumazet @ 2018-02-05 15:52 UTC (permalink / raw)
  To: Ilya Lesokhin, netdev, kafai; +Cc: borisp

On Mon, 2018-02-05 at 17:11 +0200, Ilya Lesokhin wrote:
> Avoid SKB coalescing if eor bit is set in one of the relevant
> SKBs.
> 
> Fixes: c134ecb87817 ("tcp: Make use of MSG_EOR in tcp_sendmsg")
> Signed-off-by: Ilya Lesokhin <ilyal@mellanox.com>
> ---

Reviewed-by: Eric Dumazet <edumazet@google.com>

Thanks.

^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH 1/1] tcp: Honor the eor bit in tcp_mtu_probe
  2018-02-05 15:52 ` Eric Dumazet
@ 2018-02-05 17:10   ` Eric Dumazet
  0 siblings, 0 replies; 4+ messages in thread
From: Eric Dumazet @ 2018-02-05 17:10 UTC (permalink / raw)
  To: Ilya Lesokhin, netdev, kafai; +Cc: borisp

On Mon, 2018-02-05 at 07:52 -0800, Eric Dumazet wrote:
> On Mon, 2018-02-05 at 17:11 +0200, Ilya Lesokhin wrote:
> > Avoid SKB coalescing if eor bit is set in one of the relevant
> > SKBs.
> > 
> > Fixes: c134ecb87817 ("tcp: Make use of MSG_EOR in tcp_sendmsg")
> > Signed-off-by: Ilya Lesokhin <ilyal@mellanox.com>
> > ---
> 
> Reviewed-by: Eric Dumazet <edumazet@google.com>
> 
> Thanks.


I am taking this approval back.

You missed an eor propagation if it is in the last skb that is copied
to the new skb.

Something like this added to your patch :

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index e9f985e42405a38fc95980da5debb7ac8b51fbb5..87c2ff458f7528ee3cd3e5e1154375a906c1bc67 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2134,6 +2134,7 @@ static int tcp_mtu_probe(struct sock *sk)
 			/* We've eaten all the data from this skb.
 			 * Throw it away. */
 			TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags;
+			TCP_SKB_CB(nskb)->eor = TCP_SKB_CB(skb)->eor;
 			tcp_unlink_write_queue(skb, sk);
 			sk_wmem_free_skb(sk, skb);
 		} else {

^ permalink raw reply related	[flat|nested] 4+ messages in thread

* Re: [PATCH 1/1] tcp: Honor the eor bit in tcp_mtu_probe
  2018-02-05 15:11 [PATCH 1/1] tcp: Honor the eor bit in tcp_mtu_probe Ilya Lesokhin
  2018-02-05 15:52 ` Eric Dumazet
@ 2018-02-06 21:29 ` kbuild test robot
  1 sibling, 0 replies; 4+ messages in thread
From: kbuild test robot @ 2018-02-06 21:29 UTC (permalink / raw)
  To: Ilya Lesokhin; +Cc: kbuild-all, netdev, kafai, borisp, Ilya Lesokhin

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Hi Ilya,

I love your patch! Perhaps something to improve:

[auto build test WARNING on net/master]
[also build test WARNING on v4.15 next-20180206]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Ilya-Lesokhin/tcp-Honor-the-eor-bit-in-tcp_mtu_probe/20180207-045040
config: i386-randconfig-x007-201805 (attached as .config)
compiler: gcc-7 (Debian 7.2.0-12) 7.2.1 20171025
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

Note: it may well be a FALSE warning. FWIW you are at least aware of it now.
http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings

All warnings (new ones prefixed by >>):

   In file included from include/linux/tcp.h:21:0,
                    from include/net/tcp.h:24,
                    from net//ipv4/tcp_output.c:39:
   net//ipv4/tcp_output.c: In function 'tcp_write_xmit':
>> include/linux/skbuff.h:3196:12: warning: 'skb' may be used uninitialized in this function [-Wmaybe-uninitialized]
      for (tmp = skb->next;      \
               ^
   net//ipv4/tcp_output.c:2043:18: note: 'skb' was declared here
     struct sk_buff *skb, *nskb, *next;
                     ^~~
--
   In file included from include/linux/tcp.h:21:0,
                    from include/net/tcp.h:24,
                    from net/ipv4/tcp_output.c:39:
   net/ipv4/tcp_output.c: In function 'tcp_write_xmit':
>> include/linux/skbuff.h:3196:12: warning: 'skb' may be used uninitialized in this function [-Wmaybe-uninitialized]
      for (tmp = skb->next;      \
               ^
   net/ipv4/tcp_output.c:2043:18: note: 'skb' was declared here
     struct sk_buff *skb, *nskb, *next;
                     ^~~

vim +/skb +3196 include/linux/skbuff.h

18a4c0eab Eric Dumazet    2017-10-05  3168  
^1da177e4 Linus Torvalds  2005-04-16  3169  #define skb_queue_walk(queue, skb) \
^1da177e4 Linus Torvalds  2005-04-16  3170  		for (skb = (queue)->next;					\
a1e4891fd Linus Torvalds  2011-05-22  3171  		     skb != (struct sk_buff *)(queue);				\
^1da177e4 Linus Torvalds  2005-04-16  3172  		     skb = skb->next)
^1da177e4 Linus Torvalds  2005-04-16  3173  
46f8914e5 James Chapman   2007-04-30  3174  #define skb_queue_walk_safe(queue, skb, tmp)					\
46f8914e5 James Chapman   2007-04-30  3175  		for (skb = (queue)->next, tmp = skb->next;			\
46f8914e5 James Chapman   2007-04-30  3176  		     skb != (struct sk_buff *)(queue);				\
46f8914e5 James Chapman   2007-04-30  3177  		     skb = tmp, tmp = skb->next)
46f8914e5 James Chapman   2007-04-30  3178  
1164f52a2 David S. Miller 2008-09-23  3179  #define skb_queue_walk_from(queue, skb)						\
a1e4891fd Linus Torvalds  2011-05-22  3180  		for (; skb != (struct sk_buff *)(queue);			\
1164f52a2 David S. Miller 2008-09-23  3181  		     skb = skb->next)
1164f52a2 David S. Miller 2008-09-23  3182  
18a4c0eab Eric Dumazet    2017-10-05  3183  #define skb_rbtree_walk(skb, root)						\
18a4c0eab Eric Dumazet    2017-10-05  3184  		for (skb = skb_rb_first(root); skb != NULL;			\
18a4c0eab Eric Dumazet    2017-10-05  3185  		     skb = skb_rb_next(skb))
18a4c0eab Eric Dumazet    2017-10-05  3186  
18a4c0eab Eric Dumazet    2017-10-05  3187  #define skb_rbtree_walk_from(skb)						\
18a4c0eab Eric Dumazet    2017-10-05  3188  		for (; skb != NULL;						\
18a4c0eab Eric Dumazet    2017-10-05  3189  		     skb = skb_rb_next(skb))
18a4c0eab Eric Dumazet    2017-10-05  3190  
18a4c0eab Eric Dumazet    2017-10-05  3191  #define skb_rbtree_walk_from_safe(skb, tmp)					\
18a4c0eab Eric Dumazet    2017-10-05  3192  		for (; tmp = skb ? skb_rb_next(skb) : NULL, (skb != NULL);	\
18a4c0eab Eric Dumazet    2017-10-05  3193  		     skb = tmp)
18a4c0eab Eric Dumazet    2017-10-05  3194  
1164f52a2 David S. Miller 2008-09-23  3195  #define skb_queue_walk_from_safe(queue, skb, tmp)				\
1164f52a2 David S. Miller 2008-09-23 @3196  		for (tmp = skb->next;						\
1164f52a2 David S. Miller 2008-09-23  3197  		     skb != (struct sk_buff *)(queue);				\
1164f52a2 David S. Miller 2008-09-23  3198  		     skb = tmp, tmp = skb->next)
1164f52a2 David S. Miller 2008-09-23  3199  

:::::: The code at line 3196 was first introduced by commit
:::::: 1164f52a244204830c7625b3c22812781996d7b4 net: Add skb_queue_walk_from() and skb_queue_walk_from_safe().

:::::: TO: David S. Miller <davem@davemloft.net>
:::::: CC: David S. Miller <davem@davemloft.net>

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

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2018-02-05 15:11 [PATCH 1/1] tcp: Honor the eor bit in tcp_mtu_probe Ilya Lesokhin
2018-02-05 15:52 ` Eric Dumazet
2018-02-05 17:10   ` Eric Dumazet
2018-02-06 21:29 ` kbuild test robot

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