iptables-restore: support acquiring the lock.
Currently, ip[6]tables-restore does not perform any locking, so it
is not safe to use concurrently with ip[6]tables.
This patch makes ip[6]tables-restore wait for the lock if -w
was specified. Arguments to -w and -W are supported in the same
was as they are in ip[6]tables.
The lock is not acquired on startup. Instead, it is acquired when
a new table handle is created (on encountering '*') and released
when the table is committed (COMMIT). This makes it possible to
keep long-running iptables-restore processes in the background
(for example, reading commands from a pipe opened by a system
management daemon) and simultaneously run iptables commands.
If -w is not specified, then the command proceeds without taking
the lock.
Tested as follows:
1. Run iptables-restore -w, and check that iptables commands work
with or without -w.
2. Type "*filter" into the iptables-restore input. Verify that
a) ip[6]tables commands without -w fail with "another app is
currently holding the xtables lock...".
b) ip[6]tables commands with "-w 2" fail after 2 seconds.
c) ip[6]tables commands with "-w" hang until "COMMIT" is
typed into the iptables-restore window.
3. With the lock held by an ip6tables-restore process:
strace -e flock /tmp/iptables/sbin/iptables-restore -w 1 -W 100000
shows 11 calls to flock and fails.
4. Run an iptables-restore with -w and one without -w, and check:
a) Type "*filter" in the first and then the second, and the
second exits with an error.
b) Type "*filter" in the second and "*filter" "-S" "COMMIT"
into the first. The rules are listed only when the first
copy sees "COMMIT".
Signed-off-by: Narayan Kamath <narayan@google.com>
Signed-off-by: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
(cherry picked from commit 999eaa241212d3952ddff39a99d0d55a74e3639e)
Bug: 36108349
Test: see top of change stack.
Change-Id: I2a51fab1c169763db00124641459dde2ed6c4c97
diff --git a/iptables/ip6tables-restore.c b/iptables/ip6tables-restore.c
index 632525b..7d40590 100644
--- a/iptables/ip6tables-restore.c
+++ b/iptables/ip6tables-restore.c
@@ -15,6 +15,7 @@
#include <stdio.h>
#include <stdlib.h>
#include "ip6tables.h"
+#include "xshared.h"
#include "xtables.h"
#include "libiptc/libip6tc.h"
#include "ip6tables-multi.h"
@@ -25,17 +26,23 @@
#define DEBUGP(x, args...)
#endif
-static int counters = 0, verbose = 0, noflush = 0;
+static int counters = 0, verbose = 0, noflush = 0, wait = 0;
+
+static struct timeval wait_interval = {
+ .tv_sec = 1,
+};
/* Keeping track of external matches and targets. */
static const struct option options[] = {
- {.name = "counters", .has_arg = false, .val = 'c'},
- {.name = "verbose", .has_arg = false, .val = 'v'},
- {.name = "test", .has_arg = false, .val = 't'},
- {.name = "help", .has_arg = false, .val = 'h'},
- {.name = "noflush", .has_arg = false, .val = 'n'},
- {.name = "modprobe", .has_arg = true, .val = 'M'},
- {.name = "table", .has_arg = true, .val = 'T'},
+ {.name = "counters", .has_arg = 0, .val = 'c'},
+ {.name = "verbose", .has_arg = 0, .val = 'v'},
+ {.name = "test", .has_arg = 0, .val = 't'},
+ {.name = "help", .has_arg = 0, .val = 'h'},
+ {.name = "noflush", .has_arg = 0, .val = 'n'},
+ {.name = "modprobe", .has_arg = 1, .val = 'M'},
+ {.name = "table", .has_arg = 1, .val = 'T'},
+ {.name = "wait", .has_arg = 2, .val = 'w'},
+ {.name = "wait-interval", .has_arg = 2, .val = 'W'},
{NULL},
};
@@ -43,14 +50,16 @@
static void print_usage(const char *name, const char *version)
{
- fprintf(stderr, "Usage: %s [-c] [-v] [-t] [-h] [-n] [-T table] [-M command]\n"
+ fprintf(stderr, "Usage: %s [-c] [-v] [-t] [-h] [-n] [-w secs] [-W usecs] [-T table] [-M command]\n"
" [ --counters ]\n"
" [ --verbose ]\n"
" [ --test ]\n"
" [ --help ]\n"
" [ --noflush ]\n"
+ " [ --wait=<seconds>\n"
+ " [ --wait-interval=<usecs>\n"
" [ --table=<TABLE> ]\n"
- " [ --modprobe=<command> ]\n", name);
+ " [ --modprobe=<command> ]\n", name);
exit(1);
}
@@ -181,7 +190,7 @@
{
struct xtc_handle *handle = NULL;
char buffer[10240];
- int c;
+ int c, lock;
char curtable[XT_TABLE_MAXNAMELEN + 1];
FILE *in;
int in_table = 0, testing = 0;
@@ -189,6 +198,7 @@
const struct xtc_ops *ops = &ip6tc_ops;
line = 0;
+ lock = XT_LOCK_NOT_ACQUIRED;
ip6tables_globals.program_name = "ip6tables-restore";
c = xtables_init_all(&ip6tables_globals, NFPROTO_IPV6);
@@ -203,7 +213,7 @@
init_extensions6();
#endif
- while ((c = getopt_long(argc, argv, "bcvthnM:T:", options, NULL)) != -1) {
+ while ((c = getopt_long(argc, argv, "bcvthnwWM:T:", options, NULL)) != -1) {
switch (c) {
case 'b':
fprintf(stderr, "-b/--binary option is not implemented\n");
@@ -224,6 +234,12 @@
case 'n':
noflush = 1;
break;
+ case 'w':
+ wait = parse_wait_time(argc, argv);
+ break;
+ case 'W':
+ parse_wait_interval(argc, argv, &wait_interval);
+ break;
case 'M':
xtables_modprobe_program = optarg;
break;
@@ -270,8 +286,23 @@
DEBUGP("Not calling commit, testing\n");
ret = 1;
}
+
+ /* Done with the current table, release the lock. */
+ if (lock >= 0) {
+ xtables_unlock(lock);
+ lock = XT_LOCK_NOT_ACQUIRED;
+ }
+
in_table = 0;
} else if ((buffer[0] == '*') && (!in_table)) {
+ /* Acquire a lock before we create a new table handle */
+ lock = xtables_lock(wait, &wait_interval);
+ if (lock == XT_LOCK_BUSY) {
+ fprintf(stderr, "Another app is currently holding the xtables lock. "
+ "Perhaps you want to use the -w option?\n");
+ exit(RESOURCE_PROBLEM);
+ }
+
/* New table */
char *table;
diff --git a/iptables/ip6tables.c b/iptables/ip6tables.c
index 4d77721..579d347 100644
--- a/iptables/ip6tables.c
+++ b/iptables/ip6tables.c
@@ -1779,7 +1779,7 @@
generic_opt_check(command, cs.options);
/* Attempt to acquire the xtables lock */
- if (!restore && !xtables_lock(wait, &wait_interval)) {
+ if (!restore && xtables_lock(wait, &wait_interval) == XT_LOCK_BUSY) {
fprintf(stderr, "Another app is currently holding the xtables lock. ");
if (wait == 0)
fprintf(stderr, "Perhaps you want to use the -w option?\n");
diff --git a/iptables/iptables-restore.c b/iptables/iptables-restore.c
index 12f9e24..113045d 100644
--- a/iptables/iptables-restore.c
+++ b/iptables/iptables-restore.c
@@ -12,6 +12,7 @@
#include <stdio.h>
#include <stdlib.h>
#include "iptables.h"
+#include "xshared.h"
#include "xtables.h"
#include "libiptc/libiptc.h"
#include "iptables-multi.h"
@@ -22,17 +23,23 @@
#define DEBUGP(x, args...)
#endif
-static int counters = 0, verbose = 0, noflush = 0;
+static int counters = 0, verbose = 0, noflush = 0, wait = 0;
+
+static struct timeval wait_interval = {
+ .tv_sec = 1,
+};
/* Keeping track of external matches and targets. */
static const struct option options[] = {
- {.name = "counters", .has_arg = false, .val = 'c'},
- {.name = "verbose", .has_arg = false, .val = 'v'},
- {.name = "test", .has_arg = false, .val = 't'},
- {.name = "help", .has_arg = false, .val = 'h'},
- {.name = "noflush", .has_arg = false, .val = 'n'},
- {.name = "modprobe", .has_arg = true, .val = 'M'},
- {.name = "table", .has_arg = true, .val = 'T'},
+ {.name = "counters", .has_arg = 0, .val = 'c'},
+ {.name = "verbose", .has_arg = 0, .val = 'v'},
+ {.name = "test", .has_arg = 0, .val = 't'},
+ {.name = "help", .has_arg = 0, .val = 'h'},
+ {.name = "noflush", .has_arg = 0, .val = 'n'},
+ {.name = "modprobe", .has_arg = 1, .val = 'M'},
+ {.name = "table", .has_arg = 1, .val = 'T'},
+ {.name = "wait", .has_arg = 2, .val = 'w'},
+ {.name = "wait-interval", .has_arg = 2, .val = 'W'},
{NULL},
};
@@ -42,14 +49,16 @@
static void print_usage(const char *name, const char *version)
{
- fprintf(stderr, "Usage: %s [-c] [-v] [-t] [-h] [-n] [-T table] [-M command]\n"
+ fprintf(stderr, "Usage: %s [-c] [-v] [-t] [-h] [-n] [-w secs] [-W usecs] [-T table] [-M command]\n"
" [ --counters ]\n"
" [ --verbose ]\n"
" [ --test ]\n"
" [ --help ]\n"
" [ --noflush ]\n"
+ " [ --wait=<seconds>\n"
+ " [ --wait-interval=<usecs>\n"
" [ --table=<TABLE> ]\n"
- " [ --modprobe=<command> ]\n", name);
+ " [ --modprobe=<command> ]\n", name);
exit(1);
}
@@ -180,7 +189,7 @@
{
struct xtc_handle *handle = NULL;
char buffer[10240];
- int c;
+ int c, lock;
char curtable[XT_TABLE_MAXNAMELEN + 1];
FILE *in;
int in_table = 0, testing = 0;
@@ -188,6 +197,7 @@
const struct xtc_ops *ops = &iptc_ops;
line = 0;
+ lock = XT_LOCK_NOT_ACQUIRED;
iptables_globals.program_name = "iptables-restore";
c = xtables_init_all(&iptables_globals, NFPROTO_IPV4);
@@ -202,7 +212,7 @@
init_extensions4();
#endif
- while ((c = getopt_long(argc, argv, "bcvthnM:T:", options, NULL)) != -1) {
+ while ((c = getopt_long(argc, argv, "bcvthnwWM:T:", options, NULL)) != -1) {
switch (c) {
case 'b':
fprintf(stderr, "-b/--binary option is not implemented\n");
@@ -223,6 +233,12 @@
case 'n':
noflush = 1;
break;
+ case 'w':
+ wait = parse_wait_time(argc, argv);
+ break;
+ case 'W':
+ parse_wait_interval(argc, argv, &wait_interval);
+ break;
case 'M':
xtables_modprobe_program = optarg;
break;
@@ -269,8 +285,23 @@
DEBUGP("Not calling commit, testing\n");
ret = 1;
}
+
+ /* Done with the current table, release the lock. */
+ if (lock >= 0) {
+ xtables_unlock(lock);
+ lock = XT_LOCK_NOT_ACQUIRED;
+ }
+
in_table = 0;
} else if ((buffer[0] == '*') && (!in_table)) {
+ /* Acquire a lock before we create a new table handle */
+ lock = xtables_lock(wait, &wait_interval);
+ if (lock == XT_LOCK_BUSY) {
+ fprintf(stderr, "Another app is currently holding the xtables lock. "
+ "Perhaps you want to use the -w option?\n");
+ exit(RESOURCE_PROBLEM);
+ }
+
/* New table */
char *table;
diff --git a/iptables/iptables.c b/iptables/iptables.c
index 04be5ab..62731c5 100644
--- a/iptables/iptables.c
+++ b/iptables/iptables.c
@@ -1766,7 +1766,7 @@
generic_opt_check(command, cs.options);
/* Attempt to acquire the xtables lock */
- if (!restore && !xtables_lock(wait, &wait_interval)) {
+ if (!restore && xtables_lock(wait, &wait_interval) == XT_LOCK_BUSY) {
fprintf(stderr, "Another app is currently holding the xtables lock. ");
if (wait == 0)
fprintf(stderr, "Perhaps you want to use the -w option?\n");
diff --git a/iptables/xshared.c b/iptables/xshared.c
index 06147d1..3fbe3b1 100644
--- a/iptables/xshared.c
+++ b/iptables/xshared.c
@@ -246,7 +246,7 @@
match->init(match->m);
}
-bool xtables_lock(int wait, struct timeval *wait_interval)
+int xtables_lock(int wait, struct timeval *wait_interval)
{
struct timeval time_left, wait_time;
int fd, i = 0;
@@ -256,22 +256,22 @@
fd = open(XT_LOCK_NAME, O_CREAT, 0600);
if (fd < 0)
- return true;
+ return XT_LOCK_UNSUPPORTED;
if (wait == -1) {
if (flock(fd, LOCK_EX) == 0)
- return true;
+ return fd;
fprintf(stderr, "Can't lock %s: %s\n", XT_LOCK_NAME,
strerror(errno));
- return false;
+ return XT_LOCK_BUSY;
}
while (1) {
if (flock(fd, LOCK_EX | LOCK_NB) == 0)
- return true;
+ return fd;
else if (timercmp(&time_left, wait_interval, <))
- return false;
+ return XT_LOCK_BUSY;
if (++i % 10 == 0) {
fprintf(stderr, "Another app is currently holding the xtables lock; "
@@ -285,6 +285,12 @@
}
}
+void xtables_unlock(int lock)
+{
+ if (lock >= 0)
+ close(lock);
+}
+
int parse_wait_time(int argc, char *argv[])
{
int wait = -1;
diff --git a/iptables/xshared.h b/iptables/xshared.h
index d8a697a..539e6c2 100644
--- a/iptables/xshared.h
+++ b/iptables/xshared.h
@@ -86,7 +86,28 @@
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 *);
-bool xtables_lock(int wait, struct timeval *wait_interval);
+
+/**
+ * Values for the iptables lock.
+ *
+ * A value >= 0 indicates the lock filedescriptor. Other values are:
+ *
+ * XT_LOCK_UNSUPPORTED : The system does not support locking, execution will
+ * proceed lockless.
+ *
+ * XT_LOCK_BUSY : The lock was held by another process. xtables_lock only
+ * returns this value when |wait| == false. If |wait| == true, xtables_lock
+ * will not return unless the lock has been acquired.
+ *
+ * XT_LOCK_NOT_ACQUIRED : We have not yet attempted to acquire the lock.
+ */
+enum {
+ XT_LOCK_BUSY = -1,
+ XT_LOCK_UNSUPPORTED = -2,
+ XT_LOCK_NOT_ACQUIRED = -3,
+};
+extern int xtables_lock(int wait, struct timeval *tv);
+extern void xtables_unlock(int lock);
int parse_wait_time(int argc, char *argv[]);
void parse_wait_interval(int argc, char *argv[], struct timeval *wait_interval);
