Re: [LTP] recvfrom01: fix test for invalid message flags

[Jan Stancek <jstancek@redhat.com>]

----- Original Message -----
> From: "Chuck Ebbert" <cebbert.lkml@gmail.com>
> To: ltp-list@lists.sourceforge.net
> Sent: Thursday, 2 October, 2014 12:10:32 AM
> Subject: [LTP] recvfrom01: fix test for invalid message flags
> 


> Note that this introduces a failure on kernels before 3.17, which has
> a bug fix for MSG_ERRQUEUE flag handling. This failure is a legitimate
> bug on these older kernels. (They should not be returning success with
> no data available.)

I hit a failure in this testcase while trying latest LTP before release.
Are you sure this is a bug?

Looking at commit history and man-pages, this looks more like new feature to me,
flag that has not been supported before and now it is.

"MSG_ERRQUEUE is illegal on SOCK_STREAM sockets." [1]
"TCP timestamping introduced MSG_ERRQUEUE handling for TCP sockets." [2][3]

Until commit [3], tcp_recvmsg() has ignored this flag and it was also documented
that way. So, I don't see why TFAIL is valid result on <3.17 for MSG_ERRQUEUE test:

 socket(PF_INET, SOCK_STREAM, IPPROTO_IP) = 3
 connect(3, {sa_family=AF_INET, sin_port=htons(59273), sin_addr=inet_addr("0.0.0.0")}, 16) = 0
 select(4, [3], NULL, NULL, {2, 0})      = 1 (in [3], left {1, 999998})
 recvfrom(3, "hoser\n", 1024, MSG_ERRQUEUE, NULL, NULL) = 6

Regards,
Jan

[1] https://lkml.org/lkml/2006/9/18/182
[2] f4713a3dfad045d46afcb9c2a7d0bba288920ed4
[3] 4ed2d765dfaccff5ebdac68e2064b59125033a3b

> 
> [1] http://marc.info/?t=141148149900006&r=1&w=2
> 
> ---
> 
> Additional test cases for invalid flags could be added after these two.
> And the recv01 and recvmsg01 tests need still need to be fixed, assuming
> this is the right solution.
> 
> --- a/testcases/kernel/syscalls/recvfrom/recvfrom01.c
> +++ b/testcases/kernel/syscalls/recvfrom/recvfrom01.c
> @@ -115,9 +115,14 @@
>  		    -1, EFAULT, setup1, cleanup1, "invalid recv buffer"},
>  /* 6 */
>  	{
> -	PF_INET, SOCK_STREAM, 0, (void *)buf, sizeof(buf), -1,
> +	PF_INET, SOCK_STREAM, 0, (void *)buf, sizeof(buf), MSG_OOB,
>  		    (struct sockaddr *)&from, &fromlen,
> -		    -1, EINVAL, setup1, cleanup1, "invalid flags set"},};
> +		    -1, EINVAL, setup1, cleanup1, "invalid MSG_OOB flag set"},
> +/* 7 */
> +	{
> +	PF_INET, SOCK_STREAM, 0, (void *)buf, sizeof(buf), MSG_ERRQUEUE,
> +		    (struct sockaddr *)&from, &fromlen,
> +		    -1, EAGAIN, setup1, cleanup1, "invalid MSG_ERRQUEUE flag set"},};
>  
>  int TST_TOTAL = sizeof(tdat) / sizeof(tdat[0]);
>  
> 
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