Hello Elie,
On Sat, Dec 15, 2012 at 6:44 PM, Elie De Brauwer
<eliedebrauwer@xxxxxxxxx> wrote:
> Hello all,
>
> Updated my patch with the comment from Michael (thanks for the feedback btw).
> I however did not include the shell session using netcat for the simple
> reason that the output of netcat does not illustrate that the call functions
> correctly. The output of netcat would be the same no matter how much
> UDP datagrams were created in the transmission, the only reason why I showed
> it in my previous e-mail was to avoid the generation of icmp port
> unreachable which would break my tcpdump capture. This latter one is what I
> really wanted to show, but i think that one's a bit too far fetched to be
> held in a manpage.
Fair enough.
I've applied this patch for 3.45.
Cheers,
Michael
> ---
> man2/sendmmsg.2 | 70 +++++++++++++++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 68 insertions(+), 2 deletions(-)
>
> diff --git a/man2/sendmmsg.2 b/man2/sendmmsg.2
> index 12ad3ff..b426b4d 100644
> --- a/man2/sendmmsg.2
> +++ b/man2/sendmmsg.2
> @@ -23,8 +23,6 @@
> .\" Formatted or processed versions of this manual, if unaccompanied by
> .\" the source, must acknowledge the copyright and authors of this work.
> .\"
> -.\" FIXME Adding an example program would improve this page
> -.\"
> .TH SENDMMSG 2 2012-02-27 "Linux" "Linux Programmer's Manual"
> .SH NAME
> sendmmsg \- send multiple messages on a socket
> @@ -165,6 +163,74 @@ is capped to
> .\" For error handling an application using sendmmsg needs to retry at
> .\" the first unsent message, so capping is simpler and requires less
> .\" application logic than returning EINVAL.
> +.SH EXAMPLE
> +The example below uses
> +.BR sendmmsg ()
> +to send
> +.I onetwo
> +and
> +.I three
> +in two distinct UDP datagrams using one system call. The contents
> +of the first datagram originates from a pair of buffers.
> +
> +.nf
> +#define _GNU_SOURCE
> +#include <netinet/ip.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <sys/types.h>
> +#include <sys/socket.h>
> +
> +int
> +main()
> +{
> + int sockfd;
> + struct sockaddr_in sa;
> + struct mmsghdr msg[2];
> + struct iovec msg1[2], msg2;
> + int retval;
> +
> + sockfd = socket(AF_INET, SOCK_DGRAM, 0);
> + if (sockfd == \-1) {
> + perror("socket()");
> + exit(EXIT_FAILURE);
> + }
> +
> + sa.sin_family = AF_INET;
> + sa.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
> + sa.sin_port = htons(1234);
> + if (connect(sockfd, (struct sockaddr *) &sa, sizeof(sa))) {
> + perror("connect()");
> + exit(EXIT_FAILURE);
> + }
> +
> + memset(msg1, 0, sizeof(msg1));
> + msg1[0].iov_base = "one";
> + msg1[0].iov_len = 3;
> + msg1[1].iov_base = "two";
> + msg1[1].iov_len = 3;
> +
> + memset(&msg2, 0, sizeof(msg2));
> + msg2.iov_base = "three";
> + msg2.iov_len = 5;
> +
> + memset(msg, 0, sizeof(msg));
> + msg[0].msg_hdr.msg_iov = msg1;
> + msg[0].msg_hdr.msg_iovlen = 2;
> +
> + msg[1].msg_hdr.msg_iov = &msg2;
> + msg[1].msg_hdr.msg_iovlen = 1;
> +
> + retval = sendmmsg(sockfd, msg, 2, 0);
> + if (retval == -1)
> + perror("sendmmsg()");
> + else
> + printf("%d messages sent\\n", retval);
> +
> + exit(0);
> +}
> +.fi
> .SH SEE ALSO
> .BR recvmmsg (2),
> .BR sendmsg (2),
> --
> 1.7.10.4
>
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Author of "The Linux Programming Interface"; http://man7.org/tlpi/
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