David S. Miller writes:
> From: Mateus Cordeiro Inssa <mateus@ifnet.com.br>
> Date: Mon, 31 Jan 2000 09:13:57 -0200 (BRDT)
>
> Of course the application check for errors, but the error always
> occur in the first recvfrom. The application doesn't change any
> socket property, so I assume it is on blocking mode.
>
> The sequence is: socket, bind, select,recvfrom. No one uses any
> extra param.
>
> Right, and if recvfrom returns an error, the sockaddr structure
> holds garbage. It's contents cannot be relied upon, and what
> I get from your report is that the sockaddr passed to recvfrom
> is the same one which gets passed to sendto/sendmsg. That is
> wrong, and is what causes the problem. The application in question
> needs to be fixed if this is the case.
Just to clarify: I'm not the original poster. Yes, the talkd must be
fixed, my application not (because it checks if the error occurs).
Look:
socket(PF_INET, SOCK_STREAM, IPPROTO_IP) = 4
bind(4, {sin_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("0.0.0.0")}, 16) = 0
listen(4, 20) = 0
socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) = 5
bind(5, {sin_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr("0.0.0.0")}, 16) = 0
select(12, [4 5], NULL, NULL, NULL) = 1 (in [5])
recvfrom(5, "\323x\1\0\0\1\0\0\0\0\0\0\3ola\4"..., 512, 0, {sa_family=0, sa_data="\0\0\0\0\0\0\0\0\0\0\0\0\0\0"}, [16]) = 29
| 00000 d3 78 01 00 00 01 00 00 00 00 00 00 03 6f 6c 61 .x...... .....ola |
| 00010 04 68 6f 6d 65 02 62 72 00 00 01 00 01 .home.br ..... |
# Oh, why do I have the packet, the lenght is right (errno is not set)
and the sockaddr is completely wrong ?
# And, in the second turn...
select(12, [4 5], NULL, NULL, NULL) = 1 (in [5])
recvfrom(5, "\323x\1\0\0\1\0\0\0\0\0\0\3ola\4"..., 512, 0, {sin_family=AF_INET, sin_port=htons(1026), sin_addr=inet_addr("10.0.0.13")}, [16]) = 29
| 00000 d3 78 01 00 00 01 00 00 00 00 00 00 03 6f 6c 61 .x...... .....ola |
| 00010 04 68 6f 6d 65 02 62 72 00 00 01 00 01 .home.br ..... |
Why the first (only the first) pass in this loop gives the error ?
[]'s
Mateus Cordeiro Inssa
---------------------
Linux User: 76186 Kernel: 2.3.40
ICQ (Licq): 15243895
---------------------
mateus@ifnet.com.br
mateus@cwb.fnn.net
Mon Jan 31 11:57:16 BRDT 2000
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