From mboxrd@z Thu Jan  1 00:00:00 1970
From: Daniel Borkmann <dborkman@redhat.com>
Date: Fri, 03 Jan 2014 15:47:59 +0000
Subject: Re: [lksctp-tools] [1.0.15] Regression test broken due to test_1_to_1_sockopt - SO_SNDBUF
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References: <52C6D85C.2020407@nsn.com>
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To: linux-sctp@vger.kernel.org

On 01/03/2014 04:33 PM, Matija Glavinic Pecotic wrote:
> Hello sctp folks,
>
> sctp regression suite is currently broken due to test_1_to_1_sockopt.
>
> Problem is following:
>
> TEST17 sets SO_SNDBUF to 2048
>
> TEST18 gets SO_SNDBUF, expected is 2x2048, but obtained value is 4480
>
>> test_1_to_1_sockopt.c 17 PASS : setsockopt() SO_SNDBUF - SUCCESS
>> test_1_to_1_sockopt.c 18 PASS : getsockopt() SO_SNDBUF - SUCCESS
>> test_1_to_1_sockopt.c 19 BROK : Comparison failed:Set value and got value differs Set Value@96 Get ValueD80
>
> reason lies is net/core/sock.c
>
>> 	case SO_SNDBUF:
>> 		/* Don't error on this BSD doesn't and if you think
>> 		 * about it this is right. Otherwise apps have to
>> 		 * play 'guess the biggest size' games. RCVBUF/SNDBUF
>> 		 * are treated in BSD as hints
>> 		 */
>> 		val = min_t(u32, val, sysctl_wmem_max);
>> set_sndbuf:
>> 		sk->sk_userlocks |= SOCK_SNDBUF_LOCK;
>> 		sk->sk_sndbuf = max_t(u32, val * 2, SOCK_MIN_SNDBUF);
>
> since SOCK_MIN_SNDBUF is defined as:
>
> include/net/sock.h
>> /* Since sk_{r,w}mem_alloc sums skb->truesize, even a small frame might
>>   * need sizeof(sk_buff) + MTU + padding, unless net driver perform copybreak.
>>   * Note: for send buffers, TCP works better if we can build two skbs at
>>   * minimum.
>>   */
>> #define TCP_SKB_MIN_TRUESIZE	(2048 + SKB_DATA_ALIGN(sizeof(struct sk_buff)))
>>
>> #define SOCK_MIN_SNDBUF		(TCP_SKB_MIN_TRUESIZE * 2)
>> #define SOCK_MIN_RCVBUF		 TCP_SKB_MIN_TRUESIZE
>
> we can observe that value for which we set SO_SNDBUF in TEST17 in test_1_to_1_sockopt.c needs to be increased
>
> Version is visible in subject, 1.0.15, I hope http://sourceforge.net/projects/lksctp/files/ is still valid place to get it.

Already fixed in the current git tree (see lksctp.org) under
b7ad1afc16cb0c5 ("tests: fix test_1_to_1_sockopt sock buff test
case".) Will do a release some time next week.

> Best regards,
>
> Matija
>
> PS: happy new year!
> --
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