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authorPhil Oester <kernel@linuxace.com>2013-05-31 09:07:04 -0400
committerPablo Neira Ayuso <pablo@netfilter.org>2013-06-11 12:54:30 +0200
commit93587a04d0f2511e108bbc4d87a8b9d28a5c5dd8 (patch)
treedcaf19625096fac37cddcc80a0ff1aff673c2579 /iptables
parent34844da8f53ec80b34ad094f2fca2519a7079ec2 (diff)
ip[6]tables: Add locking to prevent concurrent instances
There have been numerous complaints and bug reports over the years when admins attempt to run more than one instance of iptables simultaneously. Currently open bug reports which are related: 325: Parallel execution of the iptables is impossible 758: Retry iptables command on transient failure 764: Doing -Z twice in parallel breaks counters 822: iptables shows negative or other bad packet/byte counts As Patrick notes in 325: "Since this has been a problem people keep running into, I'd suggest to simply add some locking to iptables to catch the most common case." I started looking into alternatives to add locking, and of course the most common/obvious solution is to use a pidfile. But this has various downsides, such as if the application is terminated abnormally and the pidfile isn't cleaned up. And this also requires a writable filesystem. Using a UNIX domain socket file (e.g. in /var/run) has similar issues. Starting in 2.2, Linux added support for abstract sockets. These sockets require no filesystem, and automatically disappear once the application terminates. This is the locking solution I chose to implement in ip[6]tables. As an added bonus, since each network namespace has its own socket pool, an ip[6]tables instance running in one namespace will not lock out an ip[6]tables instance running in another namespace. A filesystem approach would have to recognize and handle multiple network namespaces. Signed-off-by: Phil Oester <kernel@linuxace.com> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Diffstat (limited to 'iptables')
-rw-r--r--iptables/ip6tables.8.in7
-rw-r--r--iptables/ip6tables.c17
-rw-r--r--iptables/iptables.8.in7
-rw-r--r--iptables/iptables.c17
-rw-r--r--iptables/xshared.c33
-rw-r--r--iptables/xshared.h2
6 files changed, 81 insertions, 2 deletions
diff --git a/iptables/ip6tables.8.in b/iptables/ip6tables.8.in
index 05e0d0f7..5b2a7d76 100644
--- a/iptables/ip6tables.8.in
+++ b/iptables/ip6tables.8.in
@@ -363,6 +363,13 @@ For appending, insertion, deletion and replacement, this causes
detailed information on the rule or rules to be printed. \fB\-v\fP may be
specified multiple times to possibly emit more detailed debug statements.
.TP
+\fB\-w\fP, \fB\-\-wait\fP
+Wait for the xtables lock.
+To prevent multiple instances of the program from running concurrently,
+an attempt will be made to obtain an exclusive lock at launch. By default,
+the program will exit if the lock cannot be obtained. This option will
+make the program wait until the exclusive lock can be obtained.
+.TP
\fB\-n\fP, \fB\-\-numeric\fP
Numeric output.
IP addresses and port numbers will be printed in numeric format.
diff --git a/iptables/ip6tables.c b/iptables/ip6tables.c
index c8d34e2d..eededee1 100644
--- a/iptables/ip6tables.c
+++ b/iptables/ip6tables.c
@@ -102,6 +102,7 @@ static struct option original_opts[] = {
{.name = "numeric", .has_arg = 0, .val = 'n'},
{.name = "out-interface", .has_arg = 1, .val = 'o'},
{.name = "verbose", .has_arg = 0, .val = 'v'},
+ {.name = "wait", .has_arg = 0, .val = 'w'},
{.name = "exact", .has_arg = 0, .val = 'x'},
{.name = "version", .has_arg = 0, .val = 'V'},
{.name = "help", .has_arg = 2, .val = 'h'},
@@ -257,6 +258,7 @@ exit_printhelp(const struct xtables_rule_match *matches)
" network interface name ([+] for wildcard)\n"
" --table -t table table to manipulate (default: `filter')\n"
" --verbose -v verbose mode\n"
+" --wait -w wait for the xtables lock\n"
" --line-numbers print line numbers when listing\n"
" --exact -x expand numbers (display exact values)\n"
/*"[!] --fragment -f match second or further fragments only\n"*/
@@ -1293,6 +1295,7 @@ int do_command6(int argc, char *argv[], char **table, struct xtc_handle **handle
struct in6_addr *smasks = NULL, *dmasks = NULL;
int verbose = 0;
+ bool wait = false;
const char *chain = NULL;
const char *shostnetworkmask = NULL, *dhostnetworkmask = NULL;
const char *policy = NULL, *newname = NULL;
@@ -1328,7 +1331,7 @@ int do_command6(int argc, char *argv[], char **table, struct xtc_handle **handle
opts = xt_params->orig_opts;
while ((cs.c = getopt_long(argc, argv,
- "-:A:C:D:R:I:L::S::M:F::Z::N:X::E:P:Vh::o:p:s:d:j:i:bvnt:m:xc:g:46",
+ "-:A:C:D:R:I:L::S::M:F::Z::N:X::E:P:Vh::o:p:s:d:j:i:bvwnt:m:xc:g:46",
opts, NULL)) != -1) {
switch (cs.c) {
/*
@@ -1573,6 +1576,10 @@ int do_command6(int argc, char *argv[], char **table, struct xtc_handle **handle
verbose++;
break;
+ case 'w':
+ wait = true;
+ break;
+
case 'm':
command_match(&cs);
break;
@@ -1724,6 +1731,14 @@ int do_command6(int argc, char *argv[], char **table, struct xtc_handle **handle
"chain name `%s' too long (must be under %u chars)",
chain, XT_EXTENSION_MAXNAMELEN);
+ /* Attempt to acquire the xtables lock */
+ if (!xtables_lock(wait)) {
+ fprintf(stderr, "Another app is currently holding the xtables lock. "
+ "Perhaps you want to use the -w option?\n");
+ xtables_free_opts(1);
+ exit(RESOURCE_PROBLEM);
+ }
+
/* only allocate handle if we weren't called with a handle */
if (!*handle)
*handle = ip6tc_init(*table);
diff --git a/iptables/iptables.8.in b/iptables/iptables.8.in
index 0fba603d..6f310039 100644
--- a/iptables/iptables.8.in
+++ b/iptables/iptables.8.in
@@ -351,6 +351,13 @@ For appending, insertion, deletion and replacement, this causes
detailed information on the rule or rules to be printed. \fB\-v\fP may be
specified multiple times to possibly emit more detailed debug statements.
.TP
+\fB\-w\fP, \fB\-\-wait\fP
+Wait for the xtables lock.
+To prevent multiple instances of the program from running concurrently,
+an attempt will be made to obtain an exclusive lock at launch. By default,
+the program will exit if the lock cannot be obtained. This option will
+make the program wait until the exclusive lock can be obtained.
+.TP
\fB\-n\fP, \fB\-\-numeric\fP
Numeric output.
IP addresses and port numbers will be printed in numeric format.
diff --git a/iptables/iptables.c b/iptables/iptables.c
index 79fa37b1..f857bebc 100644
--- a/iptables/iptables.c
+++ b/iptables/iptables.c
@@ -99,6 +99,7 @@ static struct option original_opts[] = {
{.name = "numeric", .has_arg = 0, .val = 'n'},
{.name = "out-interface", .has_arg = 1, .val = 'o'},
{.name = "verbose", .has_arg = 0, .val = 'v'},
+ {.name = "wait", .has_arg = 0, .val = 'w'},
{.name = "exact", .has_arg = 0, .val = 'x'},
{.name = "fragments", .has_arg = 0, .val = 'f'},
{.name = "version", .has_arg = 0, .val = 'V'},
@@ -251,6 +252,7 @@ exit_printhelp(const struct xtables_rule_match *matches)
" network interface name ([+] for wildcard)\n"
" --table -t table table to manipulate (default: `filter')\n"
" --verbose -v verbose mode\n"
+" --wait -w wait for the xtables lock\n"
" --line-numbers print line numbers when listing\n"
" --exact -x expand numbers (display exact values)\n"
"[!] --fragment -f match second or further fragments only\n"
@@ -1289,6 +1291,7 @@ int do_command4(int argc, char *argv[], char **table, struct xtc_handle **handle
struct in_addr *daddrs = NULL, *dmasks = NULL;
int verbose = 0;
+ bool wait = false;
const char *chain = NULL;
const char *shostnetworkmask = NULL, *dhostnetworkmask = NULL;
const char *policy = NULL, *newname = NULL;
@@ -1324,7 +1327,7 @@ int do_command4(int argc, char *argv[], char **table, struct xtc_handle **handle
opts = xt_params->orig_opts;
while ((cs.c = getopt_long(argc, argv,
- "-:A:C:D:R:I:L::S::M:F::Z::N:X::E:P:Vh::o:p:s:d:j:i:fbvnt:m:xc:g:46",
+ "-:A:C:D:R:I:L::S::M:F::Z::N:X::E:P:Vh::o:p:s:d:j:i:fbvwnt:m:xc:g:46",
opts, NULL)) != -1) {
switch (cs.c) {
/*
@@ -1567,6 +1570,10 @@ int do_command4(int argc, char *argv[], char **table, struct xtc_handle **handle
verbose++;
break;
+ case 'w':
+ wait = true;
+ break;
+
case 'm':
command_match(&cs);
break;
@@ -1721,6 +1728,14 @@ int do_command4(int argc, char *argv[], char **table, struct xtc_handle **handle
"chain name `%s' too long (must be under %u chars)",
chain, XT_EXTENSION_MAXNAMELEN);
+ /* Attempt to acquire the xtables lock */
+ if (!xtables_lock(wait)) {
+ fprintf(stderr, "Another app is currently holding the xtables lock. "
+ "Perhaps you want to use the -w option?\n");
+ xtables_free_opts(1);
+ exit(RESOURCE_PROBLEM);
+ }
+
/* only allocate handle if we weren't called with a handle */
if (!*handle)
*handle = iptc_init(*table);
diff --git a/iptables/xshared.c b/iptables/xshared.c
index e61c28c8..6c9992ed 100644
--- a/iptables/xshared.c
+++ b/iptables/xshared.c
@@ -6,9 +6,15 @@
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <unistd.h>
#include <xtables.h>
#include "xshared.h"
+#define XT_SOCKET_NAME "xtables"
+#define XT_SOCKET_LEN 8
+
/*
* Print out any special helps. A user might like to be able to add a --help
* to the commandline, and see expected results. So we call help for all
@@ -236,3 +242,30 @@ void xs_init_match(struct xtables_match *match)
if (match->init != NULL)
match->init(match->m);
}
+
+bool xtables_lock(bool wait)
+{
+ int i = 0, ret, xt_socket;
+ struct sockaddr_un xt_addr;
+
+ memset(&xt_addr, 0, sizeof(xt_addr));
+ xt_addr.sun_family = AF_UNIX;
+ strcpy(xt_addr.sun_path+1, XT_SOCKET_NAME);
+ xt_socket = socket(AF_UNIX, SOCK_STREAM, 0);
+ /* If we can't even create a socket, fall back to prior (lockless) behavior */
+ if (xt_socket < 0)
+ return true;
+
+ while (1) {
+ ret = bind(xt_socket, (struct sockaddr*)&xt_addr,
+ offsetof(struct sockaddr_un, sun_path)+XT_SOCKET_LEN);
+ if (ret == 0)
+ return true;
+ else if (wait == false)
+ return false;
+ if (++i % 2 == 0)
+ fprintf(stderr, "Another app is currently holding the xtables lock; "
+ "waiting for it to exit...\n");
+ sleep(1);
+ }
+}
diff --git a/iptables/xshared.h b/iptables/xshared.h
index b804aafe..1e2b9b8e 100644
--- a/iptables/xshared.h
+++ b/iptables/xshared.h
@@ -2,6 +2,7 @@
#define IPTABLES_XSHARED_H 1
#include <limits.h>
+#include <stdbool.h>
#include <stdint.h>
#include <netinet/in.h>
#include <net/if.h>
@@ -83,6 +84,7 @@ extern struct xtables_match *load_proto(struct iptables_command_state *);
extern int subcmd_main(int, char **, const struct subcommand *);
extern void xs_init_target(struct xtables_target *);
extern void xs_init_match(struct xtables_match *);
+extern bool xtables_lock(bool wait);
extern const struct xtables_afinfo *afinfo;