Hi Tycho, On 11/28/22 21:58, Tycho Andersen wrote:
Our group recently had some confusion around this. Although f327722042df
("socket.7: Explain effect of SO_SNDTIMEO for connect()") adds a mention of
connect(2), the wording around "Timeouts only have effect for system
calls that perform socket I/O" is slightly confusing: is connect(2) I/O?.
I believe it is, because of the following table used in the same page:
┌──────────────────────────────────────────────────────────────────────┐
│ I/O events │
├───────────┬───────────┬──────────────────────────────────────────────┤
│Event │ Poll flag │ Occurrence │
├───────────┼───────────┼──────────────────────────────────────────────┤
│Read │ POLLIN │ New data arrived. │
├───────────┼───────────┼──────────────────────────────────────────────┤
│Read │ POLLIN │ A connection setup has been completed (for │
│ │ │ connection‐oriented sockets) │
├───────────┼───────────┼──────────────────────────────────────────────┤
│Read │ POLLHUP │ A disconnection request has been initiated │
│ │ │ by the other end. │
├───────────┼───────────┼──────────────────────────────────────────────┤
│Read │ POLLHUP │ A connection is broken (only for connection‐ │
│ │ │ oriented protocols). When the socket is │
│ │ │ written SIGPIPE is also sent. │
├───────────┼───────────┼──────────────────────────────────────────────┤
│Write │ POLLOUT │ Socket has enough send buffer space for │
│ │ │ writing new data. │
├───────────┼───────────┼──────────────────────────────────────────────┤
│Read/Write │ POLLIN | │ An outgoing connect(2) finished. │
│ │ POLLOUT │ │
├───────────┼───────────┼──────────────────────────────────────────────┤
│Read/Write │ POLLERR │ An asynchronous error occurred. │
├───────────┼───────────┼──────────────────────────────────────────────┤
│Read/Write │ POLLHUP │ The other end has shut down one direction. │
├───────────┼───────────┼──────────────────────────────────────────────┤
│Exception │ POLLPRI │ Urgent data arrived. SIGURG is sent then. │
└───────────┴───────────┴──────────────────────────────────────────────┘
But I agree with you that it's unclear.
Let's just add connect(2) to the list of things that time out explicitly to avoid any confusion.
So, yes, I like your patch. So, patch applied.
Test program for grins: #include <stdio.h> #include <sys/socket.h> #include <netinet/ip.h> #include <arpa/inet.h>
BTW, I'm curious, how did you get the headers in the commit message? I always have a space before the # to avoid git doing harmful stuff.
Cheers, AlexP.S.: I don't know if you could please review some patches about which you may be more familiar than I am. The are somewhat related to this. They are here:
<https://lore.kernel.org/linux-man/20221122153027.10943-1-henri.van.de.water@xxxxxxxxx/T/#t> <https://lore.kernel.org/linux-man/2d4d8b7b-5890-cd9f-061d-6d259d8ed6ee@xxxxxxxxx/T/#t>
int main(void)
{
struct sockaddr_in servaddr = {
/* tycho.pizza */
.sin_addr.s_addr = inet_addr("192.241.255.151"),
.sin_port = htons(443),
.sin_family = AF_INET,
};
int fd;
struct timeval timeout = {
.tv_sec = 0,
.tv_usec = 100,
};
fd = socket(AF_INET, SOCK_STREAM, 0);
if (fd < 0) {
perror("socket");
return 1;
}
if (setsockopt(fd, SOL_SOCKET, SO_SNDTIMEO, &timeout, sizeof(timeout)) < 0) {
perror("setsockopt");
return 1;
}
if (connect(fd, (struct sockaddr *)&servaddr, sizeof(servaddr)) < 0) {
perror("connect");
return 1;
}
printf("connect successful\n");
return 0;
}
$ ./so_sndtimeo
connect: Operation now in progress
Signed-off-by: Tycho Andersen <tycho@tycho.pizza>
---
man7/socket.7 | 1 +
1 file changed, 1 insertion(+)
diff --git a/man7/socket.7 b/man7/socket.7
index 2b191c783..c3c13cda6 100644
--- a/man7/socket.7
+++ b/man7/socket.7
@@ -838,6 +838,7 @@ just as if the socket was specified to be nonblocking.
If the timeout is set to zero (the default),
then the operation will never timeout.
Timeouts only have effect for system calls that perform socket I/O (e.g.,
+.BR connect (2),
.BR read (2),
.BR recvmsg (2),
.BR send (2),
base-commit: 60eb580d1e836977d57355b6519f32e37bdc3392
-- <http://www.alejandro-colomar.es/>
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