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Date:   Thu, 7 May 2020 09:15:15 -0700
From:   sdf@...gle.com
To:     Martin KaFai Lau <kafai@...com>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org, davem@...emloft.net,
        ast@...nel.org, daniel@...earbox.net, Andrey Ignatov <rdna@...com>
Subject: Re: [PATCH bpf-next v3 1/5] selftests/bpf: generalize helpers to
 control background listener

On 05/06, Martin KaFai Lau wrote:
> On Wed, May 06, 2020 at 03:32:06PM -0700, Stanislav Fomichev wrote:
> > Move the following routines that let us start a background listener
> > thread and connect to a server by fd to the test_prog:
> > * start_server_thread - start background INADDR_ANY thread
> > * stop_server_thread - stop the thread
> > * connect_to_fd - connect to the server identified by fd
> >
> > These will be used in the next commit.
> >
> > Also, extend these helpers to support AF_INET6 and accept the family
> > as an argument.
> >
> > v3:
> > * export extra helper to start server without a thread (Martin KaFai  
> Lau)
> >
> > v2:
> > * put helpers into network_helpers.c (Andrii Nakryiko)
> >
> > Cc: Andrey Ignatov <rdna@...com>
> > Cc: Martin KaFai Lau <kafai@...com>
> > Signed-off-by: Stanislav Fomichev <sdf@...gle.com>
> > ---
> >  tools/testing/selftests/bpf/Makefile          |   2 +-
> >  tools/testing/selftests/bpf/network_helpers.c | 164 ++++++++++++++++++
> >  tools/testing/selftests/bpf/network_helpers.h |  12 ++
> >  .../selftests/bpf/prog_tests/tcp_rtt.c        | 116 +------------
> >  4 files changed, 181 insertions(+), 113 deletions(-)
> >  create mode 100644 tools/testing/selftests/bpf/network_helpers.c
> >  create mode 100644 tools/testing/selftests/bpf/network_helpers.h
> >
> > diff --git a/tools/testing/selftests/bpf/Makefile  
> b/tools/testing/selftests/bpf/Makefile
> > index 3d942be23d09..8f25966b500b 100644
> > --- a/tools/testing/selftests/bpf/Makefile
> > +++ b/tools/testing/selftests/bpf/Makefile
> > @@ -354,7 +354,7 @@ endef
> >  TRUNNER_TESTS_DIR := prog_tests
> >  TRUNNER_BPF_PROGS_DIR := progs
> >  TRUNNER_EXTRA_SOURCES := test_progs.c cgroup_helpers.c trace_helpers.c	 
> \
> > -			 flow_dissector_load.h
> > +			 network_helpers.c flow_dissector_load.h
> >  TRUNNER_EXTRA_FILES := $(OUTPUT)/urandom_read				\
> >  		       $(wildcard progs/btf_dump_test_case_*.c)
> >  TRUNNER_BPF_BUILD_RULE := CLANG_BPF_BUILD_RULE
> > diff --git a/tools/testing/selftests/bpf/network_helpers.c  
> b/tools/testing/selftests/bpf/network_helpers.c
> > new file mode 100644
> > index 000000000000..6ad16dfebfb2
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/network_helpers.c
> > @@ -0,0 +1,164 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +#include <errno.h>
> > +#include <pthread.h>
> > +#include <stdbool.h>
> > +#include <stdio.h>
> > +#include <string.h>
> > +#include <unistd.h>
> > +#include <linux/err.h>
> > +#include <linux/in.h>
> > +#include <linux/in6.h>
> > +
> > +#include "network_helpers.h"
> > +
> > +#define CHECK_FAIL(condition) ({					\
> > +	int __ret = !!(condition);					\
> > +	int __save_errno = errno;					\
> > +	if (__ret) {							\
> > +		fprintf(stdout, "%s:FAIL:%d\n", __func__, __LINE__);	\
> > +	}								\
> > +	errno = __save_errno;						\
> > +	__ret;								\
> > +})
> > +
> > +#define clean_errno() (errno == 0 ? "None" : strerror(errno))
> > +#define log_err(MSG, ...) fprintf(stderr, "(%s:%d: errno: %s) "  
> MSG "\n", \
> > +	__FILE__, __LINE__, clean_errno(), ##__VA_ARGS__)
> > +
> > +int start_server(int family, int type)
> > +{
> > +	struct sockaddr_storage addr = {};
> > +	socklen_t len;
> > +	int fd;
> > +
> > +	if (family == AF_INET) {
> > +		struct sockaddr_in *sin = (void *)&addr;
> > +
> > +		sin->sin_family = AF_INET;
> > +		len = sizeof(*sin);
> > +	} else {
> > +		struct sockaddr_in6 *sin6 = (void *)&addr;
> > +
> > +		sin6->sin6_family = AF_INET6;
> > +		len = sizeof(*sin6);
> > +	}
> > +
> > +	fd = socket(family, type | SOCK_NONBLOCK, 0);
> > +	if (fd < 0) {
> > +		log_err("Failed to create server socket");
> > +		return -1;
> > +	}
> > +
> > +	if (bind(fd, (const struct sockaddr *)&addr, len) < 0) {
> > +		log_err("Failed to bind socket");
> > +		close(fd);
> > +		return -1;
> > +	}
> > +
> > +	if (type == SOCK_STREAM) {
> > +		if (listen(fd, 1) < 0) {
> > +			log_err("Failed to listed on socket");
> > +			close(fd);
> > +			return -1;
> > +		}
> > +	}
> > +
> > +	return fd;
> > +}
> > +
> > +static pthread_mutex_t server_started_mtx = PTHREAD_MUTEX_INITIALIZER;
> > +static pthread_cond_t server_started = PTHREAD_COND_INITIALIZER;
> > +static volatile bool server_done;
> > +pthread_t server_tid;
> > +
> > +static void *server_thread(void *arg)
> > +{
> > +	struct sockaddr_storage addr;
> > +	socklen_t len = sizeof(addr);
> > +	int fd = *(int *)arg;
> > +	int client_fd;
> > +
> > +	pthread_mutex_lock(&server_started_mtx);
> > +	pthread_cond_signal(&server_started);
> > +	pthread_mutex_unlock(&server_started_mtx);
> > +
> > +	while (true) {
> > +		client_fd = accept(fd, (struct sockaddr *)&addr, &len);
> > +		if (client_fd == -1 && errno == EAGAIN) {
> > +			usleep(50);
> > +			continue;
> > +		}
> > +		break;
> > +	}
> > +	if (CHECK_FAIL(client_fd < 0)) {
> > +		perror("Failed to accept client");
> > +		return ERR_PTR(-1);
> > +	}
> > +
> > +	while (!server_done)
> > +		usleep(50);
> > +
> > +	close(client_fd);
> > +
> > +	return NULL;
> > +}
> > +
> > +int start_server_thread(int family, int type)
> > +{
> > +	int fd = start_server(family, type);
> > +
> > +	if (fd < 0)
> > +		return -1;
> > +
> > +	if (CHECK_FAIL(pthread_create(&server_tid, NULL, server_thread,
> > +				      (void *)&fd)))
> > +		goto err;
> > +
> > +	pthread_mutex_lock(&server_started_mtx);
> > +	pthread_cond_wait(&server_started, &server_started_mtx);
> > +	pthread_mutex_unlock(&server_started_mtx);
> > +
> > +	return fd;
> > +err:
> > +	close(fd);
> > +	return -1;
> > +}
> > +
> > +void stop_server_thread(int fd)
> > +{
> > +	void *server_res;
> > +
> > +	server_done = true;
> > +	CHECK_FAIL(pthread_join(server_tid, &server_res));
> > +	CHECK_FAIL(IS_ERR(server_res));
> > +	close(fd);
> > +}
> > +
> > +int connect_to_fd(int family, int type, int server_fd)
> > +{
> > +	struct sockaddr_storage addr;
> > +	socklen_t len = sizeof(addr);
> > +	int fd;
> > +
> > +	fd = socket(family, type, 0);
> > +	if (fd < 0) {
> > +		log_err("Failed to create client socket");
> > +		return -1;
> > +	}
> > +
> > +	if (getsockname(server_fd, (struct sockaddr *)&addr, &len)) {
> > +		log_err("Failed to get server addr");
> > +		goto out;
> > +	}
> > +
> > +	if (connect(fd, (const struct sockaddr *)&addr, len) < 0) {
> > +		log_err("Fail to connect to server with family %d", family);
> > +		goto out;
> > +	}
> > +
> > +	return fd;
> > +
> > +out:
> > +	close(fd);
> > +	return -1;
> > +}
> > diff --git a/tools/testing/selftests/bpf/network_helpers.h  
> b/tools/testing/selftests/bpf/network_helpers.h
> > new file mode 100644
> > index 000000000000..4ed31706b7f4
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/network_helpers.h
> > @@ -0,0 +1,12 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +#ifndef __NETWORK_HELPERS_H
> > +#define __NETWORK_HELPERS_H
> > +#include <sys/socket.h>
> > +#include <sys/types.h>
> > +
> > +int start_server(int family, int type);
> > +int start_server_thread(int family, int type);
> > +void stop_server_thread(int fd);
> > +int connect_to_fd(int family, int type, int server_fd);
> > +
> > +#endif
> > diff --git a/tools/testing/selftests/bpf/prog_tests/tcp_rtt.c  
> b/tools/testing/selftests/bpf/prog_tests/tcp_rtt.c
> > index e56b52ab41da..4aaa1e6e33ad 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/tcp_rtt.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/tcp_rtt.c
> > @@ -1,6 +1,7 @@
> >  // SPDX-License-Identifier: GPL-2.0
> >  #include <test_progs.h>
> >  #include "cgroup_helpers.h"
> > +#include "network_helpers.h"
> >
> >  struct tcp_rtt_storage {
> >  	__u32 invoked;
> > @@ -87,34 +88,6 @@ static int verify_sk(int map_fd, int client_fd,  
> const char *msg, __u32 invoked,
> >  	return err;
> >  }
> >
> > -static int connect_to_server(int server_fd)
> > -{
> > -	struct sockaddr_storage addr;
> > -	socklen_t len = sizeof(addr);
> > -	int fd;
> > -
> > -	fd = socket(AF_INET, SOCK_STREAM, 0);
> > -	if (fd < 0) {
> > -		log_err("Failed to create client socket");
> > -		return -1;
> > -	}
> > -
> > -	if (getsockname(server_fd, (struct sockaddr *)&addr, &len)) {
> > -		log_err("Failed to get server addr");
> > -		goto out;
> > -	}
> > -
> > -	if (connect(fd, (const struct sockaddr *)&addr, len) < 0) {
> > -		log_err("Fail to connect to server");
> > -		goto out;
> > -	}
> > -
> > -	return fd;
> > -
> > -out:
> > -	close(fd);
> > -	return -1;
> > -}
> >
> >  static int run_test(int cgroup_fd, int server_fd)
> >  {
> > @@ -145,7 +118,7 @@ static int run_test(int cgroup_fd, int server_fd)
> >  		goto close_bpf_object;
> >  	}
> >
> > -	client_fd = connect_to_server(server_fd);
> > +	client_fd = connect_to_fd(AF_INET, SOCK_STREAM, server_fd);
> >  	if (client_fd < 0) {
> >  		err = -1;
> >  		goto close_bpf_object;
> > @@ -180,103 +153,22 @@ static int run_test(int cgroup_fd, int server_fd)
> >  	return err;
> >  }
> >
> > -static int start_server(void)
> > -{
> > -	struct sockaddr_in addr = {
> > -		.sin_family = AF_INET,
> > -		.sin_addr.s_addr = htonl(INADDR_LOOPBACK),
> > -	};
> > -	int fd;
> > -
> > -	fd = socket(AF_INET, SOCK_STREAM | SOCK_NONBLOCK, 0);
> > -	if (fd < 0) {
> > -		log_err("Failed to create server socket");
> > -		return -1;
> > -	}
> > -
> > -	if (bind(fd, (const struct sockaddr *)&addr, sizeof(addr)) < 0) {
> > -		log_err("Failed to bind socket");
> > -		close(fd);
> > -		return -1;
> > -	}
> > -
> > -	return fd;
> > -}
> > -
> > -static pthread_mutex_t server_started_mtx = PTHREAD_MUTEX_INITIALIZER;
> > -static pthread_cond_t server_started = PTHREAD_COND_INITIALIZER;
> > -static volatile bool server_done = false;
> > -
> > -static void *server_thread(void *arg)
> > -{
> > -	struct sockaddr_storage addr;
> > -	socklen_t len = sizeof(addr);
> > -	int fd = *(int *)arg;
> > -	int client_fd;
> > -	int err;
> > -
> > -	err = listen(fd, 1);
> > -
> > -	pthread_mutex_lock(&server_started_mtx);
> > -	pthread_cond_signal(&server_started);
> > -	pthread_mutex_unlock(&server_started_mtx);
> > -
> > -	if (CHECK_FAIL(err < 0)) {
> > -		perror("Failed to listed on socket");
> > -		return ERR_PTR(err);
> > -	}
> > -
> > -	while (true) {
> > -		client_fd = accept(fd, (struct sockaddr *)&addr, &len);
> > -		if (client_fd == -1 && errno == EAGAIN) {
> > -			usleep(50);
> > -			continue;
> > -		}
> > -		break;
> > -	}
> > -	if (CHECK_FAIL(client_fd < 0)) {
> > -		perror("Failed to accept client");
> > -		return ERR_PTR(err);
> > -	}
> > -
> > -	while (!server_done)
> > -		usleep(50);
> > -
> > -	close(client_fd);
> > -
> > -	return NULL;
> > -}
> > -
> >  void test_tcp_rtt(void)
> >  {
> >  	int server_fd, cgroup_fd;
> > -	pthread_t tid;
> > -	void *server_res;
> >
> >  	cgroup_fd = test__join_cgroup("/tcp_rtt");
> >  	if (CHECK_FAIL(cgroup_fd < 0))
> >  		return;
> >
> > -	server_fd = start_server();
> > +	server_fd = start_server_thread(AF_INET, SOCK_STREAM);
> I still don't see a thread is needed in this existing test_tcp_rtt also.

> I was hoping the start/stop_server_thread() helpers can be removed.
> I am not positive the future tests will find start/stop_server_thread()
> useful as is because it only does accept() and there is no easy way to
> get the accept-ed() fd.

> If this test needs to keep the thread, may be only keep the
> start/stop_server_thread() in this test for now until
> there is another use case that can benefit from them.

> Keep the start_server() and connect_to_fd() in the new
> network_helpers.c.  I think at least sk_assign.c (and likely
> a few others) should be able to reuse them later.  They
> are doing something very close to start_server() and
> connect_to_fd().

> Thoughts?
I think you're right and tcp_rtt might not need a thread as well.
Let me fiddle with it a bit.

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