Re: [PATCH bpf-next v4 3/6] selftests/bpf: netns_new() and netns_free() helpers.

[Kui-Feng Lee <sinquersw@gmail.com>]

On 7/31/24 14:02, Stanislav Fomichev wrote:
> On 07/31, Kui-Feng Lee wrote:
>> netns_new()/netns_free() create/delete network namespaces. They support the
>> option '-m' of test_progs to start/stop traffic monitor for the network
>> namespace being created for matched tests.
>>
>> Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com>
>> ---
>>   tools/testing/selftests/bpf/network_helpers.c | 26 ++++++
>>   tools/testing/selftests/bpf/network_helpers.h |  2 +
>>   tools/testing/selftests/bpf/test_progs.c      | 80 +++++++++++++++++++
>>   tools/testing/selftests/bpf/test_progs.h      |  4 +
>>   4 files changed, 112 insertions(+)
>>
>> diff --git a/tools/testing/selftests/bpf/network_helpers.c b/tools/testing/selftests/bpf/network_helpers.c
>> index a3f0a49fb26f..f2cf43382a8e 100644
>> --- a/tools/testing/selftests/bpf/network_helpers.c
>> +++ b/tools/testing/selftests/bpf/network_helpers.c
>> @@ -432,6 +432,32 @@ char *ping_command(int family)
>>   	return "ping";
>>   }
>>   
>> +int make_netns(const char *name)
>> +{
> 
> [..]
> 
>> +	char cmd[128];
>> +	int r;
>> +
>> +	snprintf(cmd, sizeof(cmd), "ip netns add %s", name);
>> +	r = system(cmd);
> 
> I doubt that we're gonna see any real problems with that in the tests,
> but maybe easier to use apsrint and avoid dealing with fixed 128-byte
> string?

asprintf? Sure!

> 
>> +	if (r > 0)
>> +		/* exit code */
>> +		return -r;
>> +	return r;
>> +}
>> +
>> +int remove_netns(const char *name)
>> +{
>> +	char cmd[128];
>> +	int r;
>> +
>> +	snprintf(cmd, sizeof(cmd), "ip netns del %s >/dev/null 2>&1", name);
>> +	r = system(cmd);
>> +	if (r > 0)
>> +		/* exit code */
>> +		return -r;
>> +	return r;
>> +}
>> +
>>   struct nstoken {
>>   	int orig_netns_fd;
>>   };
>> diff --git a/tools/testing/selftests/bpf/network_helpers.h b/tools/testing/selftests/bpf/network_helpers.h
>> index cce56955371f..f8aa8680a640 100644
>> --- a/tools/testing/selftests/bpf/network_helpers.h
>> +++ b/tools/testing/selftests/bpf/network_helpers.h
>> @@ -93,6 +93,8 @@ struct nstoken;
>>   struct nstoken *open_netns(const char *name);
>>   void close_netns(struct nstoken *token);
>>   int send_recv_data(int lfd, int fd, uint32_t total_bytes);
>> +int make_netns(const char *name);
>> +int remove_netns(const char *name);
>>   
>>   static __u16 csum_fold(__u32 csum)
>>   {
>> diff --git a/tools/testing/selftests/bpf/test_progs.c b/tools/testing/selftests/bpf/test_progs.c
>> index 95643cd3119a..f86d47efe06e 100644
>> --- a/tools/testing/selftests/bpf/test_progs.c
>> +++ b/tools/testing/selftests/bpf/test_progs.c
>> @@ -1074,6 +1074,86 @@ int compare_stack_ips(int smap_fd, int amap_fd, int stack_trace_len)
>>   	return err;
>>   }
>>   
>> +struct netns_obj {
>> +	char nsname[128];
>> +	struct tmonitor_ctx *tmon;
>> +	struct nstoken *nstoken;
>> +};
>> +
>> +/* Create a new network namespace with the given name.
>> + *
>> + * Create a new network namespace and set the network namespace of the
>> + * current process to the new network namespace if the argument "open" is
>> + * true. This function should be paired with netns_free() to release the
>> + * resource and delete the network namespace.
>> + *
>> + * It also implements the functionality of the option "-m" by starting
>> + * traffic monitor on the background to capture the packets in this network
>> + * namespace if the current test or subtest matching the pattern.
>> + *
>> + * name: the name of the network namespace to create.
>> + * open: open the network namespace if true.
>> + *
>> + * Return: the network namespace object on success, NULL on failure.
>> + */
>> +struct netns_obj *netns_new(const char *name, bool open)
>> +{
>> +	struct netns_obj *netns_obj = malloc(sizeof(*netns_obj));
>> +	int r;
>> +
>> +	if (!netns_obj)
>> +		return NULL;
>> +	memset(netns_obj, 0, sizeof(*netns_obj));
>> +
>> +	strncpy(netns_obj->nsname, name, sizeof(netns_obj->nsname));
>> +	netns_obj->nsname[sizeof(netns_obj->nsname) - 1] = '\0';
> 
> Same here. Seems easier to have "char *nsname" and do
> netns_obj->nsname = strdup(name) here. Trimming the name, in theory,
> is problematic because do do remove_netns(netns_obj->nsname) later
> on (with potentially trimmed name).

You are right!

> 
> But, again, probably not a huge deal in the selftests. So up to you on
> whether you want to address it or not.