selftests/bpf: netns_new() and netns_free() helpers.

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.

Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com>
Link: https://lore.kernel.org/r/20240815053254.470944-4-thinker.li@gmail.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

tools/testing/selftests/bpf/network_helpers.c

@@ -446,6 +446,52 @@ char *ping_command(int family)
 	return "ping";
 }
 
+int remove_netns(const char *name)
+{
+	char *cmd;
+	int r;
+
+	r = asprintf(&cmd, "ip netns del %s >/dev/null 2>&1", name);
+	if (r < 0) {
+		log_err("Failed to malloc cmd");
+		return -1;
+	}
+
+	r = system(cmd);
+	free(cmd);
+	return r;
+}
+
+int make_netns(const char *name)
+{
+	char *cmd;
+	int r;
+
+	r = asprintf(&cmd, "ip netns add %s", name);
+	if (r < 0) {
+		log_err("Failed to malloc cmd");
+		return -1;
+	}
+
+	r = system(cmd);
+	free(cmd);
+
+	if (r)
+		return r;
+
+	r = asprintf(&cmd, "ip -n %s link set lo up", name);
+	if (r < 0) {
+		log_err("Failed to malloc cmd for setting up lo");
+		remove_netns(name);
+		return -1;
+	}
+
+	r = system(cmd);
+	free(cmd);
+
+	return r;
+}
+
 struct nstoken {
 	int orig_netns_fd;
 };

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)
 {

tools/testing/selftests/bpf/test_progs.c

@@ -18,6 +18,8 @@
 #include <bpf/btf.h>
 #include "json_writer.h"
 
+#include "network_helpers.h"
+
 #ifdef __GLIBC__
 #include <execinfo.h> /* backtrace */
 #endif
@@ -642,6 +644,92 @@ int compare_stack_ips(int smap_fd, int amap_fd, int stack_trace_len)
 	return err;
 }
 
+struct netns_obj {
+	char *nsname;
+	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.
+ *
+ * nsname: 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 *nsname, bool open)
+{
+	struct netns_obj *netns_obj = malloc(sizeof(*netns_obj));
+	const char *test_name, *subtest_name;
+	int r;
+
+	if (!netns_obj)
+		return NULL;
+	memset(netns_obj, 0, sizeof(*netns_obj));
+
+	netns_obj->nsname = strdup(nsname);
+	if (!netns_obj->nsname)
+		goto fail;
+
+	/* Create the network namespace */
+	r = make_netns(nsname);
+	if (r)
+		goto fail;
+
+	/* Start traffic monitor */
+	if (env.test->should_tmon ||
+	    (env.subtest_state && env.subtest_state->should_tmon)) {
+		test_name = env.test->test_name;
+		subtest_name = env.subtest_state ? env.subtest_state->name : NULL;
+		netns_obj->tmon = traffic_monitor_start(nsname, test_name, subtest_name);
+		if (!netns_obj->tmon) {
+			fprintf(stderr, "Failed to start traffic monitor for %s\n", nsname);
+			goto fail;
+		}
+	} else {
+		netns_obj->tmon = NULL;
+	}
+
+	if (open) {
+		netns_obj->nstoken = open_netns(nsname);
+		if (!netns_obj->nstoken)
+			goto fail;
+	}
+
+	return netns_obj;
+fail:
+	traffic_monitor_stop(netns_obj->tmon);
+	remove_netns(nsname);
+	free(netns_obj->nsname);
+	free(netns_obj);
+	return NULL;
+}
+
+/* Delete the network namespace.
+ *
+ * This function should be paired with netns_new() to delete the namespace
+ * created by netns_new().
+ */
+void netns_free(struct netns_obj *netns_obj)
+{
+	if (!netns_obj)
+		return;
+	traffic_monitor_stop(netns_obj->tmon);
+	close_netns(netns_obj->nstoken);
+	remove_netns(netns_obj->nsname);
+	free(netns_obj->nsname);
+	free(netns_obj);
+}
+
 /* extern declarations for test funcs */
 #define DEFINE_TEST(name)				\
 	extern void test_##name(void) __weak;		\

tools/testing/selftests/bpf/test_progs.h

@@ -430,6 +430,10 @@ int write_sysctl(const char *sysctl, const char *value);
 int get_bpf_max_tramp_links_from(struct btf *btf);
 int get_bpf_max_tramp_links(void);
 
+struct netns_obj;
+struct netns_obj *netns_new(const char *name, bool open);
+void netns_free(struct netns_obj *netns);
+
 #ifdef __x86_64__
 #define SYS_NANOSLEEP_KPROBE_NAME "__x64_sys_nanosleep"
 #elif defined(__s390x__)