[PATCH] sendmmsg.2: Updated fixme, added example

[PATCH] sendmmsg.2: Updated fixme, added example

[Elie De Brauwer]

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.

gr
E. 

---
 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

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[PATCH] recvmmsg.2: Updated fixme, added example

[Elie De Brauwer]

Hi all,

Same patch as before but I spotted a typo I made applicatoin -> application.

my 2 cents
E.

---
 man2/recvmmsg.2 |   94 +++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 92 insertions(+), 2 deletions(-)

diff --git a/man2/recvmmsg.2 b/man2/recvmmsg.2
index a7b00d4..3252be7 100644
--- a/man2/recvmmsg.2
+++ b/man2/recvmmsg.2
@@ -21,8 +21,6 @@
 .\" Formatted or processed versions of this manual, if unaccompanied by
 .\" the source, must acknowledge the copyright and authors of this work.
 .\"
-.\" FIXME: This page could be improved with an example program.
-.\"
 .TH RECVMMSG 2 2012-05-02 "Linux" "Linux Programmer's Manual"
 .SH NAME
 recvmmsg \- receive multiple messages on a socket
@@ -165,6 +163,98 @@ Support in glibc was added in version 2.12.
 .SH CONFORMING TO
 .BR recvmmsg ()
 is Linux-specific.
+.SH EXAMPLE
+.PP
+The following program uses 
+.BR recvmmsg () 
+to receive multiple messages on a socket and stores
+them in multiple buffers. The call returns of all buffers
+are filled or if the timeout specified is expired.
+
+The following 
+.BR bash (1)
+snippet periodically generates UDP datagrams containing a 
+a random number:
+.in +4n
+.nf
+.RB "$" " while true; do echo $RANDOM > /dev/udp/127.0.0.1/1234; sleep 0.25; done"
+.fi
+.in
+
+These datagrams are read by the example application which 
+can give the following output:
+.in +4n
+.nf
+.RB "$" " ./a.out"
+5 messages received
+1 11782
+2 11345
+3 304
+4 13514
+5 28421
+.fi
+.in
+.SS Program source
+\&
+.nf
+#define _GNU_SOURCE
+#include <netinet/ip.h> 
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+
+int 
+main()
+{
+#define VLEN 10
+#define BUFSIZE 200 
+#define TIMEOUT 1
+    int sockfd, retval, i;
+    struct sockaddr_in sa;
+    struct mmsghdr msgs[VLEN];
+    struct iovec iovecs[VLEN];
+    char bufs[VLEN][BUFSIZE+1];
+    struct timespec timeout;
+
+    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 (bind(sockfd, (struct sockaddr *) &sa, sizeof(sa))) {
+        perror("bind()");
+        exit(EXIT_FAILURE);
+    }
+
+    memset(msgs, 0, sizeof(msgs));
+    for (i = 0; i < VLEN; i++) {
+        iovecs[i].iov_base         = bufs[i];
+        iovecs[i].iov_len          = BUFSIZE;
+        msgs[i].msg_hdr.msg_iov    = &iovecs[i];
+        msgs[i].msg_hdr.msg_iovlen = 1;
+    }
+
+    timeout.tv_sec = TIMEOUT;
+    timeout.tv_nsec = 0;
+
+    retval = recvmmsg(sockfd, msgs, VLEN, 0, &timeout);
+    if (retval == -1)
+        perror("recvmmsg()");
+    else {
+        printf("%d messages received\n", retval);
+        for (i = 0; i < retval; i++) {
+            bufs[i][msgs[i].msg_len] = 0;
+            printf("%d %s", i+1, bufs[i]);
+        }
+    }
+    exit(EXIT_SUCCESS);
+}
+.fi 
 .SH SEE ALSO
 .BR clock_gettime (2),
 .BR recvmsg (2),
-- 
1.7.10.4

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Re: [PATCH] recvmmsg.2: Updated fixme, added example

[Michael Kerrisk (man-pages)]

Hello Elie,

Can you please resubmit with fixes as below.

On Wed, Dec 19, 2012 at 10:28 PM, Elie De Brauwer
<eliedebrauwer-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> Hi all,
>
> Same patch as before but I spotted a typo I made applicatoin -> application.
>
> my 2 cents
> E.
>
> ---
>  man2/recvmmsg.2 |   94 +++++++++++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 92 insertions(+), 2 deletions(-)
>
> diff --git a/man2/recvmmsg.2 b/man2/recvmmsg.2
> index a7b00d4..3252be7 100644
> --- a/man2/recvmmsg.2
> +++ b/man2/recvmmsg.2
> @@ -21,8 +21,6 @@
>  .\" Formatted or processed versions of this manual, if unaccompanied by
>  .\" the source, must acknowledge the copyright and authors of this work.
>  .\"
> -.\" FIXME: This page could be improved with an example program.
> -.\"
>  .TH RECVMMSG 2 2012-05-02 "Linux" "Linux Programmer's Manual"
>  .SH NAME
>  recvmmsg \- receive multiple messages on a socket
> @@ -165,6 +163,98 @@ Support in glibc was added in version 2.12.
>  .SH CONFORMING TO
>  .BR recvmmsg ()
>  is Linux-specific.
> +.SH EXAMPLE
> +.PP
> +The following program uses
> +.BR recvmmsg ()
> +to receive multiple messages on a socket and stores
> +them in multiple buffers. The call returns of all buffers

Start new sentences on new source lines.

> +are filled or if the timeout specified is expired.
> +
> +The following
> +.BR bash (1)

change to "The following shell snippet..." (We don't really care that it's bash)

> +snippet periodically generates UDP datagrams containing a
> +a random number:
> +.in +4n
> +.nf
> +.RB "$" " while true; do echo $RANDOM > /dev/udp/127.0.0.1/1234; sleep 0.25; done"
> +.fi
> +.in
> +
> +These datagrams are read by the example application which
> +can give the following output:
> +.in +4n
> +.nf
> +.RB "$" " ./a.out"
> +5 messages received
> +1 11782
> +2 11345
> +3 304
> +4 13514
> +5 28421
> +.fi
> +.in
> +.SS Program source
> +\&
> +.nf
> +#define _GNU_SOURCE
> +#include <netinet/ip.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <sys/socket.h>
> +
> +int
> +main()
> +{
> +#define VLEN 10
> +#define BUFSIZE 200
> +#define TIMEOUT 1
> +    int sockfd, retval, i;
> +    struct sockaddr_in sa;
> +    struct mmsghdr msgs[VLEN];
> +    struct iovec iovecs[VLEN];
> +    char bufs[VLEN][BUFSIZE+1];
> +    struct timespec timeout;
> +
> +    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 (bind(sockfd, (struct sockaddr *) &sa, sizeof(sa))) {

Add "== \-1" here please.

> +        perror("bind()");
> +        exit(EXIT_FAILURE);
> +    }
> +
> +    memset(msgs, 0, sizeof(msgs));
> +    for (i = 0; i < VLEN; i++) {
> +        iovecs[i].iov_base         = bufs[i];
> +        iovecs[i].iov_len          = BUFSIZE;
> +        msgs[i].msg_hdr.msg_iov    = &iovecs[i];
> +        msgs[i].msg_hdr.msg_iovlen = 1;
> +    }
> +
> +    timeout.tv_sec = TIMEOUT;
> +    timeout.tv_nsec = 0;
> +
> +    retval = recvmmsg(sockfd, msgs, VLEN, 0, &timeout);
> +    if (retval == -1)
> +        perror("recvmmsg()");
> +    else {

Make the preceding (and note the addition of the backslash).

if (retval == \-1)
    perror()
    exit(EXIT_FAILURE);
}

And then the following part does not need to sit in an 'else' branch.

> +        printf("%d messages received\n", retval);

\n should be \\n

> +        for (i = 0; i < retval; i++) {
> +            bufs[i][msgs[i].msg_len] = 0;
> +            printf("%d %s", i+1, bufs[i]);
> +        }
> +    }
> +    exit(EXIT_SUCCESS);
> +}
> +.fi
>  .SH SEE ALSO
>  .BR clock_gettime (2),
>  .BR recvmsg (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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[PATCH] recvmmsg.2 Updated fixme, added example

[Elie De Brauwer]

Hi all,

Please find below a patch with the comments in below (including two 
other typo's I seem to have missed yesterday). 

Thanks for the comments.

E.


---
 man2/recvmmsg.2 |   94 +++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 92 insertions(+), 2 deletions(-)

diff --git a/man2/recvmmsg.2 b/man2/recvmmsg.2
index a7b00d4..0c6db49 100644
--- a/man2/recvmmsg.2
+++ b/man2/recvmmsg.2
@@ -21,8 +21,6 @@
 .\" Formatted or processed versions of this manual, if unaccompanied by
 .\" the source, must acknowledge the copyright and authors of this work.
 .\"
-.\" FIXME: This page could be improved with an example program.
-.\"
 .TH RECVMMSG 2 2012-05-02 "Linux" "Linux Programmer's Manual"
 .SH NAME
 recvmmsg \- receive multiple messages on a socket
@@ -165,6 +163,98 @@ Support in glibc was added in version 2.12.
 .SH CONFORMING TO
 .BR recvmmsg ()
 is Linux-specific.
+.SH EXAMPLE
+.PP
+The following program uses 
+.BR recvmmsg () 
+to receive multiple messages on a socket and stores
+them in multiple buffers. 
+The call returns if all buffers are filled or if the 
+timeout specified is expired.
+
+The following snippet periodically generates UDP datagrams 
+containing a random number:
+.in +4n
+.nf
+.RB "$" " while true; do echo $RANDOM > /dev/udp/127.0.0.1/1234; sleep 0.25; done"
+.fi
+.in
+
+These datagrams are read by the example application which 
+can give the following output:
+.in +4n
+.nf
+.RB "$" " ./a.out"
+5 messages received
+1 11782
+2 11345
+3 304
+4 13514
+5 28421
+.fi
+.in
+.SS Program source
+\&
+.nf
+#define _GNU_SOURCE
+#include <netinet/ip.h> 
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+
+int 
+main()
+{
+#define VLEN 10
+#define BUFSIZE 200 
+#define TIMEOUT 1
+    int sockfd, retval, i;
+    struct sockaddr_in sa;
+    struct mmsghdr msgs[VLEN];
+    struct iovec iovecs[VLEN];
+    char bufs[VLEN][BUFSIZE+1];
+    struct timespec timeout;
+
+    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 (bind(sockfd, (struct sockaddr *) &sa, sizeof(sa)) == \-1) {
+        perror("bind()");
+        exit(EXIT_FAILURE);
+    }
+
+    memset(msgs, 0, sizeof(msgs));
+    for (i = 0; i < VLEN; i++) {
+        iovecs[i].iov_base         = bufs[i];
+        iovecs[i].iov_len          = BUFSIZE;
+        msgs[i].msg_hdr.msg_iov    = &iovecs[i];
+        msgs[i].msg_hdr.msg_iovlen = 1;
+    }
+
+    timeout.tv_sec = TIMEOUT;
+    timeout.tv_nsec = 0;
+
+    retval = recvmmsg(sockfd, msgs, VLEN, 0, &timeout);
+    if (retval == \-1) {
+        perror("recvmmsg()");
+        exit(EXIT_FAILURE);
+    }
+
+    printf("%d messages received\\n", retval);
+    for (i = 0; i < retval; i++) {
+        bufs[i][msgs[i].msg_len] = 0;
+        printf("%d %s", i+1, bufs[i]);
+    }
+    exit(EXIT_SUCCESS);
+}
+.fi 
 .SH SEE ALSO
 .BR clock_gettime (2),
 .BR recvmsg (2),
-- 
1.7.10.4

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Re: [PATCH] recvmmsg.2 Updated fixme, added example

[Michael Kerrisk (man-pages)]

Hello Elie,

On Thu, Dec 20, 2012 at 7:47 PM, Elie De Brauwer
<eliedebrauwer-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> Hi all,
>
> Please find below a patch with the comments in below (including two
> other typo's I seem to have missed yesterday).
>
> Thanks for the comments.

Thanks for the update. I've applied this for 3.46.

Cheers,

Michael


> ---
>  man2/recvmmsg.2 |   94 +++++++++++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 92 insertions(+), 2 deletions(-)
>
> diff --git a/man2/recvmmsg.2 b/man2/recvmmsg.2
> index a7b00d4..0c6db49 100644
> --- a/man2/recvmmsg.2
> +++ b/man2/recvmmsg.2
> @@ -21,8 +21,6 @@
>  .\" Formatted or processed versions of this manual, if unaccompanied by
>  .\" the source, must acknowledge the copyright and authors of this work.
>  .\"
> -.\" FIXME: This page could be improved with an example program.
> -.\"
>  .TH RECVMMSG 2 2012-05-02 "Linux" "Linux Programmer's Manual"
>  .SH NAME
>  recvmmsg \- receive multiple messages on a socket
> @@ -165,6 +163,98 @@ Support in glibc was added in version 2.12.
>  .SH CONFORMING TO
>  .BR recvmmsg ()
>  is Linux-specific.
> +.SH EXAMPLE
> +.PP
> +The following program uses
> +.BR recvmmsg ()
> +to receive multiple messages on a socket and stores
> +them in multiple buffers.
> +The call returns if all buffers are filled or if the
> +timeout specified is expired.
> +
> +The following snippet periodically generates UDP datagrams
> +containing a random number:
> +.in +4n
> +.nf
> +.RB "$" " while true; do echo $RANDOM > /dev/udp/127.0.0.1/1234; sleep 0.25; done"
> +.fi
> +.in
> +
> +These datagrams are read by the example application which
> +can give the following output:
> +.in +4n
> +.nf
> +.RB "$" " ./a.out"
> +5 messages received
> +1 11782
> +2 11345
> +3 304
> +4 13514
> +5 28421
> +.fi
> +.in
> +.SS Program source
> +\&
> +.nf
> +#define _GNU_SOURCE
> +#include <netinet/ip.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <sys/socket.h>
> +
> +int
> +main()
> +{
> +#define VLEN 10
> +#define BUFSIZE 200
> +#define TIMEOUT 1
> +    int sockfd, retval, i;
> +    struct sockaddr_in sa;
> +    struct mmsghdr msgs[VLEN];
> +    struct iovec iovecs[VLEN];
> +    char bufs[VLEN][BUFSIZE+1];
> +    struct timespec timeout;
> +
> +    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 (bind(sockfd, (struct sockaddr *) &sa, sizeof(sa)) == \-1) {
> +        perror("bind()");
> +        exit(EXIT_FAILURE);
> +    }
> +
> +    memset(msgs, 0, sizeof(msgs));
> +    for (i = 0; i < VLEN; i++) {
> +        iovecs[i].iov_base         = bufs[i];
> +        iovecs[i].iov_len          = BUFSIZE;
> +        msgs[i].msg_hdr.msg_iov    = &iovecs[i];
> +        msgs[i].msg_hdr.msg_iovlen = 1;
> +    }
> +
> +    timeout.tv_sec = TIMEOUT;
> +    timeout.tv_nsec = 0;
> +
> +    retval = recvmmsg(sockfd, msgs, VLEN, 0, &timeout);
> +    if (retval == \-1) {
> +        perror("recvmmsg()");
> +        exit(EXIT_FAILURE);
> +    }
> +
> +    printf("%d messages received\\n", retval);
> +    for (i = 0; i < retval; i++) {
> +        bufs[i][msgs[i].msg_len] = 0;
> +        printf("%d %s", i+1, bufs[i]);
> +    }
> +    exit(EXIT_SUCCESS);
> +}
> +.fi
>  .SH SEE ALSO
>  .BR clock_gettime (2),
>  .BR recvmsg (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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