selftests/bpf: Make ehash buckets configurable in socket iterator tests

Prepare for bucket resume tests for established TCP sockets by making
the number of ehash buckets configurable. Subsequent patches force all
established sockets into the same bucket by setting ehash_buckets to
one.

Signed-off-by: Jordan Rife <[email protected]>

Author: jrife

tools/testing/selftests/bpf/prog_tests/sock_iter_batch.c

@@ -6,6 +6,7 @@
 #include "sock_iter_batch.skel.h"
 
 #define TEST_NS "sock_iter_batch_netns"
+#define TEST_CHILD_NS "sock_iter_batch_child_netns"
 
 static const int init_batch_size = 16;
 static const int nr_soreuse = 4;
@@ -304,6 +305,7 @@ struct test_case {
 		     int *socks, int socks_len, struct sock_count *counts,
 		     int counts_len, struct bpf_link *link, int iter_fd);
 	const char *description;
+	int ehash_buckets;
 	int init_socks;
 	int max_socks;
 	int sock_type;
@@ -410,13 +412,25 @@ static struct test_case resume_tests[] = {
 static void do_resume_test(struct test_case *tc)
 {
 	struct sock_iter_batch *skel = NULL;
+	struct sock_count *counts = NULL;
 	static const __u16 port = 10001;
+	struct nstoken *nstoken = NULL;
 	struct bpf_link *link = NULL;
-	struct sock_count *counts;
 	int err, iter_fd = -1;
 	const char *addr;
 	int *fds = NULL;
 
+	if (tc->ehash_buckets) {
+		SYS_NOFAIL("ip netns del " TEST_CHILD_NS);
+		SYS(done, "sysctl -w net.ipv4.tcp_child_ehash_entries=%d",
+		    tc->ehash_buckets);
+		SYS(done, "ip netns add %s", TEST_CHILD_NS);
+		SYS(done, "ip -net %s link set dev lo up", TEST_CHILD_NS);
+		nstoken = open_netns(TEST_CHILD_NS);
+		if (!ASSERT_OK_PTR(nstoken, "open_child_netns"))
+			goto done;
+	}
+
 	counts = calloc(tc->max_socks, sizeof(*counts));
 	if (!ASSERT_OK_PTR(counts, "counts"))
 		goto done;
@@ -453,6 +467,9 @@ static void do_resume_test(struct test_case *tc)
 	tc->test(tc->family, tc->sock_type, addr, port, fds, tc->init_socks,
 		 counts, tc->max_socks, link, iter_fd);
 done:
+	close_netns(nstoken);
+	SYS_NOFAIL("ip netns del " TEST_CHILD_NS);
+	SYS_NOFAIL("sysctl -w net.ipv4.tcp_child_ehash_entries=0");
 	free(counts);
 	free_fds(fds, tc->init_socks);
 	if (iter_fd >= 0)