From: Geliang Tang <tanggeliang@kylinos.cn>

Introduces large data transfer tests (1-17 MB) to validate MPTCP socket
options under high-volume conditions, including proper EOF handling,
preparing for TCP_INQ support in subsequent patches.

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
---
 .../selftests/net/mptcp/mptcp_sockopt.c       | 90 ++++++++++++++++++-
 1 file changed, 88 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/net/mptcp/mptcp_sockopt.c b/tools/testing/selftests/net/mptcp/mptcp_sockopt.c
index 675ed2dcee9f..fc65157a41ee 100644
--- a/tools/testing/selftests/net/mptcp/mptcp_sockopt.c
+++ b/tools/testing/selftests/net/mptcp/mptcp_sockopt.c
@@ -620,10 +620,12 @@ static void connect_one_server(int fd, int unixfd)
 	/* un-block server */
 	ret = read(unixfd, buf2, 4);
 	assert(ret == 4);
-	close(unixfd);
 
 	assert(strncmp(buf2, "xmit", 4) == 0);
 
+	ret = write(unixfd, &len, sizeof(len));
+	assert(ret == (ssize_t)sizeof(len));
+
 	ret = write(fd, buf, len);
 	if (ret < 0)
 		die_perror("write");
@@ -659,14 +661,51 @@ static void connect_one_server(int fd, int unixfd)
 		total += 1; /* sequence advances due to FIN */
 
 	assert(s.mptcpi_rcv_delta ? s.mptcpi_rcv_delta == (uint64_t)total : true);
+
+	ret = read(unixfd, buf2, 4);
+	assert(strncmp(buf2, "huge", 4) == 0);
+
+	total = rand() % (16 * 1024 * 1024);
+	total += (1 * 1024 * 1024);
+
+	ret = write(unixfd, &total, sizeof(total));
+	assert(ret == (ssize_t)sizeof(total));
+
+	while (total > 0) {
+		if (total > sizeof(buf))
+			len = sizeof(buf);
+		else
+			len = total;
+
+		ret = write(fd, buf, len);
+		if (ret < 0)
+			die_perror("write");
+		total -= ret;
+
+		/* we don't have to care about buf content, only
+		 * number of total bytes sent
+		 */
+	}
+
+	ret = read(unixfd, buf2, 4);
+	assert(ret == 4);
+	assert(strncmp(buf2, "shut", 4) == 0);
+
+	ret = write(fd, buf, 1);
+	assert(ret == 1);
 	close(fd);
+	ret = write(unixfd, "closed", 6);
+	assert(ret == 6);
+
+	close(unixfd);
 }
 
 static void process_one_client(int fd, int unixfd)
 {
-	ssize_t ret, ret2, ret3;
+	ssize_t ret, ret2, ret3, tot;
 	char msg_buf[4096];
 	struct so_state s;
+	size_t expect_len;
 	char buf[4096];
 	struct iovec iov = {
 		.iov_base = buf,
@@ -678,6 +717,7 @@ static void process_one_client(int fd, int unixfd)
 		.msg_control = msg_buf,
 		.msg_controllen = sizeof(msg_buf),
 	};
+	char tmp[16];
 
 	memset(&s, 0, sizeof(s));
 	do_getsockopts(&s, fd, 0, 0);
@@ -685,6 +725,12 @@ static void process_one_client(int fd, int unixfd)
 	ret = write(unixfd, "xmit", 4);
 	assert(ret == 4);
 
+	ret = read(unixfd, &expect_len, sizeof(expect_len));
+	assert(ret == (ssize_t)sizeof(expect_len));
+
+	if (expect_len > sizeof(buf))
+		xerror("expect len %zu exceeds buffer size", expect_len);
+
 	/* read one byte, expect cmsg to return expected - 1 */
 	ret = recvmsg(fd, &msg, 0);
 	if (ret < 0)
@@ -703,6 +749,9 @@ static void process_one_client(int fd, int unixfd)
 	if (s.tcpi_rcv_delta)
 		assert(s.tcpi_rcv_delta == (uint64_t)ret);
 
+	/* should have gotten exact remainder of all pending data */
+	assert(ret == (ssize_t)expect_len - 1);
+
 	ret2 = write(fd, buf, ret);
 	if (ret2 < 0)
 		die_perror("write");
@@ -727,6 +776,43 @@ static void process_one_client(int fd, int unixfd)
 			       s.last_sample.mptcpi_bytes_acked - ret2);
 	}
 
+	/* request a large swath of data. */
+	ret = write(unixfd, "huge", 4);
+	assert(ret == 4);
+
+	ret = read(unixfd, &expect_len, sizeof(expect_len));
+	assert(ret == (ssize_t)sizeof(expect_len));
+
+	/* peer should send us a few mb of data */
+	if (expect_len <= sizeof(buf))
+		xerror("expect len %zu too small\n", expect_len);
+
+	tot = 0;
+	do {
+		iov.iov_len = sizeof(buf);
+		ret = recvmsg(fd, &msg, 0);
+		if (ret < 0)
+			die_perror("recvmsg");
+
+		tot += ret;
+	} while ((size_t)tot < expect_len);
+
+	ret = write(unixfd, "shut", 4);
+	assert(ret == 4);
+
+	/* wait for hangup. Should have received one more byte of data. */
+	ret = read(unixfd, tmp, sizeof(tmp));
+	assert(ret == 6);
+	assert(strncmp(tmp, "closed", 6) == 0);
+
+	sleep(1);
+
+	iov.iov_len = 1;
+	ret = recvmsg(fd, &msg, 0);
+	if (ret < 0)
+		die_perror("recvmsg");
+	assert(ret == 1);
+
 	/* wait for hangup */
 	iov.iov_len = 1;
 	ret3 = recvmsg(fd, &msg, 0);
-- 
2.48.1