[patch] udevd - switch socket path to abstract namespace

[patch] udevd - switch socket path to abstract namespace

[Kay Sievers]

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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)


thanks,
Kay

[-- Attachment #2: 02-abstract-namespace-socket.patch --]
[-- Type: text/plain, Size: 2032 bytes --]

===== Makefile 1.102 vs edited =====
--- 1.102/Makefile	Wed Feb  4 01:56:10 2004
+++ edited/Makefile	Thu Feb  5 01:41:19 2004
@@ -241,7 +241,6 @@
 	@echo \#define UDEV_PERMISSION_FILE	\"$(configdir)\udev.permissions\" >> $@
 	@echo \#define UDEV_BIN		\"$(DESTDIR)$(sbindir)/udev\" >> $@
 	@echo \#define UDEVD_BIN	\"$(DESTDIR)$(sbindir)/udevd\" >> $@
-	@echo \#define UDEVD_SOCK	\"$(udevdir)/\.udevd.sock\" >> $@
 	@echo \#define UDEVD_LOCK	\"$(udevdir)/\.udevd.lock\" >> $@
 
 # config files automatically generated
===== udevd.c 1.11 vs edited =====
--- 1.11/udevd.c	Thu Feb  5 01:40:44 2004
+++ edited/udevd.c	Thu Feb  5 01:42:59 2004
@@ -325,7 +325,6 @@
 		case SIGINT:
 		case SIGTERM:
 			unlink(UDEVD_LOCK);
-			unlink(UDEVD_SOCK);
 			exit(20 + signum);
 			break;
 		default:
@@ -378,9 +377,9 @@
 
 	memset(&saddr, 0x00, sizeof(saddr));
 	saddr.sun_family = AF_LOCAL;
-	strcpy(saddr.sun_path, UDEVD_SOCK);
+	/* use abstract namespace for socket path */
+	strcpy(&saddr.sun_path[1], UDEVD_SOCK_PATH);
 
-	unlink(UDEVD_SOCK);
 	ssock = socket(AF_LOCAL, SOCK_STREAM, 0);
 	if (ssock == -1) {
 		dbg("error getting socket");
@@ -426,6 +425,5 @@
 	}
 exit:
 	close(ssock);
-	unlink(UDEVD_SOCK);
 	exit(1);
 }
===== udevd.h 1.6 vs edited =====
--- 1.6/udevd.h	Mon Feb  2 03:40:48 2004
+++ edited/udevd.h	Thu Feb  5 01:41:33 2004
@@ -27,6 +27,7 @@
 #define UDEV_MAGIC			"udevd_" UDEV_VERSION
 #define EVENT_TIMEOUT_SEC		5
 #define UDEVSEND_CONNECT_RETRY		20 /* x 100 millisec */
+#define UDEVD_SOCK_PATH			"udevd"
 
 struct hotplug_msg {
 	char magic[20];
===== udevsend.c 1.15 vs edited =====
--- 1.15/udevsend.c	Thu Feb  5 01:40:44 2004
+++ edited/udevsend.c	Thu Feb  5 01:41:47 2004
@@ -161,7 +161,8 @@
 
 	memset(&saddr, 0x00, sizeof(saddr));
 	saddr.sun_family = AF_LOCAL;
-	strcpy(saddr.sun_path, UDEVD_SOCK);
+	/* use abstract namespace for socket path */
+	strcpy(&saddr.sun_path[1], UDEVD_SOCK_PATH);
 
 	/* try to connect, if it fails start daemon */
 	retval = connect(sock, (struct sockaddr *) &saddr, sizeof(saddr));

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

[Greg KH]

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¯_UNIX, path="/udev/.udevd.sock"}, 110)
> 
>   strace with abstract namespace:
>     connect(3, {sa_family¯_UNIX, path=@udevd}, 110)

That's nice to know.

Applied, thanks.

greg k-h


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

[Kay Sievers]

[-- Attachment #1: Type: text/plain, Size: 1004 bytes --]

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


[-- Attachment #2: 01-socketpathlen.patch --]
[-- Type: text/plain, Size: 1675 bytes --]

===== 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 {

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

[Greg KH]

On Thu, Feb 05, 2004 at 10:19:00AM +0100, Kay Sievers wrote:
> 
> 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.

Applied, thanks.

greg k-h


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Premiere Conference on Open Tools Development and Integration
See the breadth of Eclipse activity. February 3-5 in Anaheim, CA.
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Linux-hotplug-devel@lists.sourceforge.net
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