[PATCH] iptables: accept lock file name at runtime

[PATCH] iptables: accept lock file name at runtime

[Giuseppe Scrivano]

allow users to override at runtime the lock file to use through the
XTABLES_LOCKFILE environment variable.

It allows using iptables from a network namespace owned by an user
that has no write access to XT_LOCK_NAME (by default under /run), and
without setting up a new mount namespace.

$ XTABLES_LOCKFILE=/tmp/xtables unshare -rn iptables ...

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>
---
 iptables/xshared.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/iptables/xshared.c b/iptables/xshared.c
index c1d1371a..291f1c4b 100644
--- a/iptables/xshared.c
+++ b/iptables/xshared.c
@@ -248,13 +248,18 @@ void xs_init_match(struct xtables_match *match)
 
 static int xtables_lock(int wait, struct timeval *wait_interval)
 {
+	const *lock_file;
 	struct timeval time_left, wait_time;
 	int fd, i = 0;
 
 	time_left.tv_sec = wait;
 	time_left.tv_usec = 0;
 
-	fd = open(XT_LOCK_NAME, O_CREAT, 0600);
+	lock_file = getenv("XTABLES_LOCKFILE");
+	if (lock_file == NULL || lock_file[0] == '\0')
+		lock_file = XT_LOCK_NAME;
+
+	fd = open(lock_file, O_CREAT, 0600);
 	if (fd < 0) {
 		fprintf(stderr, "Fatal: can't open lock file %s: %s\n",
 			XT_LOCK_NAME, strerror(errno));
-- 
2.26.2

Re: [PATCH] iptables: accept lock file name at runtime

[Phil Sutter]

Hi,

On Tue, Jul 14, 2020 at 06:52:06PM +0200, Giuseppe Scrivano wrote:
> allow users to override at runtime the lock file to use through the
> XTABLES_LOCKFILE environment variable.
> 
> It allows using iptables from a network namespace owned by an user
> that has no write access to XT_LOCK_NAME (by default under /run), and
> without setting up a new mount namespace.
> 
> $ XTABLES_LOCKFILE=/tmp/xtables unshare -rn iptables ...
> 
> Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>
> ---
>  iptables/xshared.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/iptables/xshared.c b/iptables/xshared.c
> index c1d1371a..291f1c4b 100644
> --- a/iptables/xshared.c
> +++ b/iptables/xshared.c
> @@ -248,13 +248,18 @@ void xs_init_match(struct xtables_match *match)
>  
>  static int xtables_lock(int wait, struct timeval *wait_interval)
>  {
> +	const *lock_file;

This does not look right. Typo?

Cheers, Phil

Re: [PATCH] iptables: accept lock file name at runtime

[Giuseppe Scrivano]

Phil Sutter <phil@nwl.cc> writes:

> Hi,
>
> On Tue, Jul 14, 2020 at 06:52:06PM +0200, Giuseppe Scrivano wrote:
>> allow users to override at runtime the lock file to use through the
>> XTABLES_LOCKFILE environment variable.
>> 
>> It allows using iptables from a network namespace owned by an user
>> that has no write access to XT_LOCK_NAME (by default under /run), and
>> without setting up a new mount namespace.
>> 
>> $ XTABLES_LOCKFILE=/tmp/xtables unshare -rn iptables ...
>> 
>> Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>
>> ---
>>  iptables/xshared.c | 7 ++++++-
>>  1 file changed, 6 insertions(+), 1 deletion(-)
>> 
>> diff --git a/iptables/xshared.c b/iptables/xshared.c
>> index c1d1371a..291f1c4b 100644
>> --- a/iptables/xshared.c
>> +++ b/iptables/xshared.c
>> @@ -248,13 +248,18 @@ void xs_init_match(struct xtables_match *match)
>>  
>>  static int xtables_lock(int wait, struct timeval *wait_interval)
>>  {
>> +	const *lock_file;
>
> This does not look right. Typo?

yes sorry, I've messed it up.  I'll send a v2.

Thanks,
Giuseppe