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

[Stanislav Fomichev <sdf@fomichev.me>]

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?

> +	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).

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