Re: [patch] udevd - switch socket path to abstract namespace

[Kay Sievers <kay.sievers@vrfy.org>]

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On Wed, Feb 04, 2004 at 05:37:35PM -0800, Greg KH wrote:
> On Thu, Feb 05, 2004 at 02:07:48AM +0100, Kay Sievers wrote:
> > 
> > As Chris Friesen <chris_friesen@sympatico.ca> suggested, here we switch
> > the unix domains socket path to abstract namespace and get rid of the
> > socket file in the filesystem.
> > 
> > Hey, this was new to me today. So here a few words:
> >   Linux supports a abstract namespace for sockets. We don't need a
> >   physical file on the filesystem but only a unique string magically
> >   starting with the '\0' character.
> > 
> >   strace with real file:
> >     connect(3, {sa_family=AF_UNIX, path="/udev/.udevd.sock"}, 110)
> > 
> >   strace with abstract namespace:
> >     connect(3, {sa_family=AF_UNIX, path=@udevd}, 110)
> 
> That's nice to know.

It seems that the guys are no longer differ about the right size of the
socket address :)

The kernel simply takes all bytes until the specified length as the name,
so the real length should be enough.

thanks,
Kay


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===== udevd.c 1.12 vs edited =====
--- 1.12/udevd.c	Thu Feb  5 02:42:59 2004
+++ edited/udevd.c	Thu Feb  5 09:32:51 2004
@@ -360,6 +360,7 @@
 	int csock;
 	struct sockaddr_un saddr;
 	struct sockaddr_un caddr;
+	socklen_t addrlen;
 	socklen_t clen;
 	pthread_t cli_tid;
 	pthread_t mgr_msg_tid;
@@ -379,6 +380,7 @@
 	saddr.sun_family = AF_LOCAL;
 	/* use abstract namespace for socket path */
 	strcpy(&saddr.sun_path[1], UDEVD_SOCK_PATH);
+	addrlen = offsetof(struct sockaddr_un, sun_path) + strlen(saddr.sun_path+1) + 1;
 
 	ssock = socket(AF_LOCAL, SOCK_STREAM, 0);
 	if (ssock == -1) {
@@ -386,7 +388,7 @@
 		exit(1);
 	}
 
-	retval = bind(ssock, &saddr, sizeof(saddr));
+	retval = bind(ssock, &saddr, addrlen);
 	if (retval < 0) {
 		dbg("bind failed\n");
 		goto exit;
===== udevsend.c 1.16 vs edited =====
--- 1.16/udevsend.c	Thu Feb  5 02:41:47 2004
+++ edited/udevsend.c	Thu Feb  5 09:40:58 2004
@@ -29,6 +29,7 @@
 #include <errno.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <stddef.h>
 #include <string.h>
 #include <unistd.h>
 #include <time.h>
@@ -124,6 +125,7 @@
 	struct timespec tspec;
 	int sock;
 	struct sockaddr_un saddr;
+	socklen_t addrlen;
 
 #ifdef DEBUG
 	init_logging("udevsend");
@@ -163,9 +165,10 @@
 	saddr.sun_family = AF_LOCAL;
 	/* use abstract namespace for socket path */
 	strcpy(&saddr.sun_path[1], UDEVD_SOCK_PATH);
+	addrlen = offsetof(struct sockaddr_un, sun_path) + strlen(saddr.sun_path+1) + 1;
 
 	/* try to connect, if it fails start daemon */
-	retval = connect(sock, (struct sockaddr *) &saddr, sizeof(saddr));
+	retval = connect(sock, (struct sockaddr *) &saddr, addrlen);
 	if (retval != -1) {
 		goto send;
 	} else {