Hello Elie,
Thanks for this patch. See comments below.
On Fri, Dec 14, 2012 at 8:06 PM, Elie De Brauwer
<eliedebrauwer@xxxxxxxxx> wrote:
> Hello all,
>
> A patch which updates a fixme which extends man 2 sendmmsg with an example.
>
> The example uses sendmmsg to sends out a string "onetwo" on a first
> datagram,
> where both halves originate from distinct buffers and a second datagram
> contains "three", coming from a single buffer.
>
> Tested with netcat listening:
> root@ubuntu:~# nc -l -u -p 1234
> onetwothree
Could you work something like the above into the patch, as a shell
session that demonstrates the use of the program.
> And tcpdump peeking:
> root@ubuntu:~# tcpdump -c 2 -s 0 -X -ni lo tcpdump: verbose output
> suppressed, use -v or -vv for full protocol decode
> listening on lo, link-type EN10MB (Ethernet), capture size 65535 bytes
> 18:45:16.632134 IP 127.0.0.1.34715 > 127.0.0.1.1234: UDP, length 6
> 0x0000: 4500 0022 c21c 4000 4011 7aac 7f00 0001 E.."..@.@.z.....
> 0x0010: 7f00 0001 879b 04d2 000e fe21 6f6e 6574 ...........!onet
> 0x0020: 776f wo
> 18:45:16.633267 IP 127.0.0.1.34715 > 127.0.0.1.1234: UDP, length 5
> 0x0000: 4500 0021 c21d 4000 4011 7aac 7f00 0001 E..!..@.@.z.....
> 0x0010: 7f00 0001 879b 04d2 000d fe20 7468 7265 ............thre
> 0x0020: 65 e
> 2 packets captured
> 4 packets received by filter
> 0 packets dropped by kernel
>
> my 2 cents
> E.
> ---
> man2/sendmmsg.2 | 69
> +++++++++++++++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 67 insertions(+), 2 deletions(-)
>
> diff --git a/man2/sendmmsg.2 b/man2/sendmmsg.2
> index 12ad3ff..5027619 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 +163,73 @@ 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. Where the contents
s/Where the/The/
> +of the first datagram originates from multiple buffers.
s/multiple/a pair of/
> +
> +.nf
> +#define _GNU_SOURCE
> +#include <netinet/ip.h> +#include <stdio.h>
Broken line above.
> +#include <stdlib.h>
> +#include <string.h>
> +#include <sys/types.h>
> +#include <sys/socket.h>
> +
> +int main()
int
main()
[K&R style please.]
> +{
> + 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) {
All instances of '-' in code should be '\-'
> + 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))) {
if (connect(sockfd, (struct sockaddr *) &sa, sizeof(sa)) == \-1) {
(Space before '&' please.)
> + 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);
Make the \n into \\n
> +
> + exit(0);
> +}
> +.fi
> .SH SEE ALSO
> .BR recvmmsg (2),
> .BR sendmsg (2),
Thanks,
Michael
--
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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