Re: [PATCH bpf-next v2 2/2] selftests/bpf: Add pairs_redir_to_connected helper

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On Thu, Oct 05, 2023 at 10:18 PM -07, Martin KaFai Lau wrote:
> On 10/5/23 12:21 AM, Geliang Tang wrote:
>> --- a/tools/testing/selftests/bpf/prog_tests/sockmap_listen.c
>> +++ b/tools/testing/selftests/bpf/prog_tests/sockmap_listen.c
>> @@ -1336,32 +1336,22 @@ static void test_redir(struct test_sockmap_listen *skel, struct bpf_map *map,
>>   	}
>>   }
>>   -static void unix_redir_to_connected(int sotype, int sock_mapfd,
>> -			       int verd_mapfd, enum redir_mode mode)
>> +static void pairs_redir_to_connected(int cli0, int peer0, int cli1, int peer1,
>> +				     int sock_mapfd, int verd_mapfd, enum redir_mode mode)
>>   {
>>   	const char *log_prefix = redir_mode_str(mode);
>> -	int c0, c1, p0, p1;
>>   	unsigned int pass;
>>   	int err, n;
>> -	int sfd[2];
>>   	u32 key;
>>   	char b;
>>     	zero_verdict_count(verd_mapfd);
>>   -	if (socketpair(AF_UNIX, sotype | SOCK_NONBLOCK, 0, sfd))
>> -		return;
>> -	c0 = sfd[0], p0 = sfd[1];
>> -
>> -	if (socketpair(AF_UNIX, sotype | SOCK_NONBLOCK, 0, sfd))
>> -		goto close0;
>> -	c1 = sfd[0], p1 = sfd[1];
>> -
>> -	err = add_to_sockmap(sock_mapfd, p0, p1);
>> +	err = add_to_sockmap(sock_mapfd, peer0, peer1);
>>   	if (err)
>>   		goto close;
>>   -	n = write(c1, "a", 1);
>> +	n = write(cli1, "a", 1);
>>   	if (n < 0)
>>   		FAIL_ERRNO("%s: write", log_prefix);
>>   	if (n == 0)
>> @@ -1376,16 +1366,34 @@ static void unix_redir_to_connected(int sotype, int sock_mapfd,
>>   	if (pass != 1)
>>   		FAIL("%s: want pass count 1, have %d", log_prefix, pass);
>>   -	n = recv_timeout(mode == REDIR_INGRESS ? p0 : c0, &b, 1, 0,
>> IO_TIMEOUT_SEC);
>> +	n = recv_timeout(mode == REDIR_INGRESS ? peer0 : cli0, &b, 1, 0, IO_TIMEOUT_SEC);
>>   	if (n < 0)
>>   		FAIL_ERRNO("%s: recv_timeout", log_prefix);
>>   	if (n == 0)
>>   		FAIL("%s: incomplete recv", log_prefix);
>>     close:
>> -	xclose(c1);
>> -	xclose(p1);
>> -close0:
>> +	xclose(cli1);
>> +	xclose(peer1);
>> +}
>> +
>> +static void unix_redir_to_connected(int sotype, int sock_mapfd,
>> +			       int verd_mapfd, enum redir_mode mode)
>> +{
>> +	int c0, c1, p0, p1;
>> +	int sfd[2];
>> +
>> +	if (socketpair(AF_UNIX, sotype | SOCK_NONBLOCK, 0, sfd))
>> +		return;
>> +	c0 = sfd[0], p0 = sfd[1];
>> +
>> +	if (socketpair(AF_UNIX, sotype | SOCK_NONBLOCK, 0, sfd))
>> +		goto close;
>> +	c1 = sfd[0], p1 = sfd[1];
>> +
>> +	pairs_redir_to_connected(c0, p0, c1, p1, sock_mapfd, verd_mapfd, mode);
>> +
>> +close:
>>   	xclose(c0);
>>   	xclose(p0);
>>   }
>> @@ -1661,51 +1669,19 @@ static int inet_socketpair(int family, int type, int *s, int *c)
>>   static void udp_redir_to_connected(int family, int sock_mapfd, int verd_mapfd,
>>   				   enum redir_mode mode)
>>   {
>> -	const char *log_prefix = redir_mode_str(mode);
>>   	int c0, c1, p0, p1;
>> -	unsigned int pass;
>> -	int err, n;
>> -	u32 key;
>> -	char b;
>> -
>> -	zero_verdict_count(verd_mapfd);
>> +	int err;
>>     	err = inet_socketpair(family, SOCK_DGRAM, &p0, &c0);
>>   	if (err)
>>   		return;
>>   	err = inet_socketpair(family, SOCK_DGRAM, &p1, &c1);
>>   	if (err)
>> -		goto close_cli0;
>> -
>> -	err = add_to_sockmap(sock_mapfd, p0, p1);
>> -	if (err)
>> -		goto close_cli1;
>> -
>> -	n = write(c1, "a", 1);
>> -	if (n < 0)
>> -		FAIL_ERRNO("%s: write", log_prefix);
>> -	if (n == 0)
>> -		FAIL("%s: incomplete write", log_prefix);
>> -	if (n < 1)
>> -		goto close_cli1;
>> -
>> -	key = SK_PASS;
>> -	err = xbpf_map_lookup_elem(verd_mapfd, &key, &pass);
>> -	if (err)
>> -		goto close_cli1;
>> -	if (pass != 1)
>> -		FAIL("%s: want pass count 1, have %d", log_prefix, pass);
>> +		goto close;
>>   -	n = recv_timeout(mode == REDIR_INGRESS ? p0 : c0, &b, 1, 0,
>> IO_TIMEOUT_SEC);
>> -	if (n < 0)
>> -		FAIL_ERRNO("%s: recv_timeout", log_prefix);
>> -	if (n == 0)
>> -		FAIL("%s: incomplete recv", log_prefix);
>> +	pairs_redir_to_connected(c0, p0, c1, p1, sock_mapfd, verd_mapfd, mode);
>>   -close_cli1:
>> -	xclose(c1);
>> -	xclose(p1);
>> -close_cli0:
>> +close:
>>   	xclose(c0);
>>   	xclose(p0);
>
> Patch 1 is applied. Thanks.
>
> In patch 2, the xclose() here is confusing after this change. It is also
> inconsistent from how other tests in sockmap_listen.c is doing it. c0/p0 and
> c1/p1 are opened here but only c0/p0 is closed here and c1/p1 is closed in the
> pairs_redir_to_connected() above instead.

I agree with Martin.

The refactoring idea itself is nice. But, I also find it surprising that
newly extracted pairs_redir_to_connected helper takes ownership of cli1
& peer1 FDs.

For me, ideally, we would start using the __cleanup__ attribute, like we
do now in the kernel code [1], to auto-close FDs on return. That would
make error recovery and resource release less verbose.

[1] https://elixir.bootlin.com/linux/v6.5/source/include/linux/cleanup.h




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