udevd - switch socket path to abstract namespace

PATCH Applied Kay Sievers 2 participants 4 messages Feb 5, 2004 – Feb 6, 2004 Kbuild

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Kay Sievers

author

2004-02-05 01:07 UTC #0 lore raw

PATCH 1/1 udevd - switch socket path to abstract namespace

As Chris Friesen <[email protected]> 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

===== Makefile 1.102 vs edited =====

Makefile +0 -1

@@ -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 =====

udevd.c +2 -4

@@ -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 =====

udevd.h +1 -0

@@ -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 =====

udevsend.c +2 -1

@@ -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));

Greg KH

Applied

2004-02-05 01:37 UTC #1 lore raw

Quoted 10 lines · Kay Sievers

As Chris Friesen <[email protected]> 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.

Quoted 5 lines

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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Kay Sievers

author

2004-02-05 09:19 UTC #2 lore raw

In reply to Kay Sievers

Quoted 11 lines · Greg KH

Quoted 10 lines · Kay Sievers
As Chris Friesen <[email protected]> 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.

Quoted 7 lines

Quoted 5 lines
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

===== udevd.c 1.12 vs edited =====

udevd.c +3 -1

@@ -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 =====

udevsend.c +4 -1

@@ -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 {

Greg KH

Applied

2004-02-06 00:11 UTC #3 lore raw

In reply to Kay Sievers

Quoted 6 lines · Kay Sievers

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