Re: [RFC PATCH 3/3] bpf: Add sk_lookup test to use ORIGDSTADDR cmsg.

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Hi Tiago,

On 2024/9/13 17:39, Tiago Lam wrote:
This patch reuses the framework already in place for sk_lookup, allowing
it now to send a reply from the server fd directly, instead of having to
create a socket bound to the original destination address and reply from
there. It does this by passing the source address and port from where to
reply from in a IP_ORIGDSTADDR ancilliary message passed in sendmsg.

Signed-off-by: Tiago Lam <tiagolam@xxxxxxxxxxxxxx>
---
  tools/testing/selftests/bpf/prog_tests/sk_lookup.c | 70 +++++++++++++++-------
  1 file changed, 48 insertions(+), 22 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/sk_lookup.c b/tools/testing/selftests/bpf/prog_tests/sk_lookup.c
index ae87c00867ba..b99aff2e3976 100644
--- a/tools/testing/selftests/bpf/prog_tests/sk_lookup.c
+++ b/tools/testing/selftests/bpf/prog_tests/sk_lookup.c
@@ -75,6 +75,7 @@ struct test {
  	struct inet_addr listen_at;
  	enum server accept_on;
  	bool reuseport_has_conns; /* Add a connected socket to reuseport group */
+	bool dont_bind_reply; /* Don't bind, send direct from server fd. */
  };
struct cb_opts {
@@ -363,7 +364,7 @@ static void v4_to_v6(struct sockaddr_storage *ss)
  	memset(&v6->sin6_addr.s6_addr[0], 0, 10);
  }
-static int udp_recv_send(int server_fd)
+static int udp_recv_send(int server_fd, bool dont_bind_reply)
  {
  	char cmsg_buf[CMSG_SPACE(sizeof(struct sockaddr_storage))];
  	struct sockaddr_storage _src_addr = { 0 };
@@ -415,26 +416,41 @@ static int udp_recv_send(int server_fd)
  		v4_to_v6(dst_addr);
  	}
- /* Reply from original destination address. */
-	fd = start_server_addr(SOCK_DGRAM, dst_addr, sizeof(*dst_addr), NULL);
-	if (!ASSERT_OK_FD(fd, "start_server_addr")) {
-		log_err("failed to create tx socket");
-		return -1;
-	}
+	if (dont_bind_reply) {
+		/* Reply directly from server fd, specifying the source address and/or
+		 * port in struct msghdr.
+		 */
+		n = sendmsg(server_fd, &msg, 0);
+		if (CHECK(n <= 0, "sendmsg", "failed\n")) {
+			log_err("failed to send echo reply");
+			return -1;
+		}
+	} else {
+		/* Reply from original destination address. */
+		fd = socket(dst_addr->ss_family, SOCK_DGRAM, 0);
+		if (CHECK(fd < 0, "socket", "failed\n")) {
+			log_err("failed to create tx socket");
+			return -1;
+		}
Just curious, why not use start_server_addr() here like before?

-	msg.msg_control = NULL;
-	msg.msg_controllen = 0;
-	n = sendmsg(fd, &msg, 0);
-	if (CHECK(n <= 0, "sendmsg", "failed\n")) {
-		log_err("failed to send echo reply");
-		ret = -1;
-		goto out;
-	}
+		ret = bind(fd, (struct sockaddr *)dst_addr, sizeof(*dst_addr));
+		if (CHECK(ret, "bind", "failed\n")) {
+			log_err("failed to bind tx socket");
+			close(fd);
+			return ret;
+		}
- ret = 0;
-out:
-	close(fd);
-	return ret;
+		msg.msg_control = NULL;
+		msg.msg_controllen = 0;
+		n = sendmsg(fd, &msg, 0);
+		if (CHECK(n <= 0, "sendmsg", "failed\n")) {
+			log_err("failed to send echo reply");
+			close(fd);
+			return -1;
+		}
+
+		close(fd);
+	}

nit: "return 0" missed.

  }

--
Philo





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