linux-kernel - [PATCH net-next 5/7] selftests: mptcp: refactor NLMSG handling with 'proto'

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Message-Id: <20250502-net-next-mptcp-sft-inc-cover-v1-5-68eec95898fb@kernel.org>
Date: Fri, 02 May 2025 14:29:25 +0200
From: "Matthieu Baerts (NGI0)" <matttbe@...nel.org>
To: mptcp@...ts.linux.dev, Mat Martineau <martineau@...nel.org>, 
 Geliang Tang <geliang@...nel.org>, "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
 Shuah Khan <shuah@...nel.org>
Cc: netdev@...r.kernel.org, linux-kselftest@...r.kernel.org, 
 linux-kernel@...r.kernel.org, "Matthieu Baerts (NGI0)" <matttbe@...nel.org>, 
 Gang Yan <yangang@...inos.cn>
Subject: [PATCH net-next 5/7] selftests: mptcp: refactor NLMSG handling
 with 'proto'

From: Gang Yan <yangang@...inos.cn>

This patch introduces the '__u32 proto' variable to the 'send_query' and
'recv_nlmsg' functions for further extending function.

In the 'send_query' function, the inclusion of this variable makes the
structure clearer and more readable.

In the 'recv_nlmsg' function, the '__u32 proto' variable ensures that
the 'diag_info' field remains unmodified when processing IPPROTO_TCP data,
thereby preventing unintended transformation into 'mptcp_info' format.

While at it, increment iovlen directly when an item is added to simplify
this portion of the code and improve its readaility.

Co-developed-by: Geliang Tang <geliang@...nel.org>
Signed-off-by: Geliang Tang <geliang@...nel.org>
Signed-off-by: Gang Yan <yangang@...inos.cn>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@...nel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@...nel.org>
---
 tools/testing/selftests/net/mptcp/mptcp_diag.c | 38 ++++++++++++++------------
 1 file changed, 20 insertions(+), 18 deletions(-)

diff --git a/tools/testing/selftests/net/mptcp/mptcp_diag.c b/tools/testing/selftests/net/mptcp/mptcp_diag.c
index 76135aba71ad24c25c7babb6875e8a6dd7636b21..cc0326548e4ec44060da83f1f77e498bcedc82a9 100644
--- a/tools/testing/selftests/net/mptcp/mptcp_diag.c
+++ b/tools/testing/selftests/net/mptcp/mptcp_diag.c
@@ -62,7 +62,7 @@ static void die_usage(int r)
 	exit(r);
 }
 
-static void send_query(int fd, struct inet_diag_req_v2 *r)
+static void send_query(int fd, struct inet_diag_req_v2 *r, __u32 proto)
 {
 	struct sockaddr_nl nladdr = {
 		.nl_family = AF_NETLINK
@@ -80,21 +80,22 @@ static void send_query(int fd, struct inet_diag_req_v2 *r)
 	};
 	struct rtattr rta_proto;
 	struct iovec iov[6];
-	int iovlen = 1;
-	__u32 proto;
+	int iovlen = 0;
 
-	proto = IPPROTO_MPTCP;
-	rta_proto.rta_type = INET_DIAG_REQ_PROTOCOL;
-	rta_proto.rta_len = RTA_LENGTH(sizeof(proto));
-
-	iov[0] = (struct iovec) {
+	iov[iovlen++] = (struct iovec) {
 		.iov_base = &req,
 		.iov_len = sizeof(req)
 	};
-	iov[iovlen] = (struct iovec){ &rta_proto, sizeof(rta_proto)};
-	iov[iovlen + 1] = (struct iovec){ &proto, sizeof(proto)};
-	req.nlh.nlmsg_len += RTA_LENGTH(sizeof(proto));
-	iovlen += 2;
+
+	if (proto == IPPROTO_MPTCP) {
+		rta_proto.rta_type = INET_DIAG_REQ_PROTOCOL;
+		rta_proto.rta_len = RTA_LENGTH(sizeof(proto));
+
+		iov[iovlen++] = (struct iovec){ &rta_proto, sizeof(rta_proto)};
+		iov[iovlen++] = (struct iovec){ &proto, sizeof(proto)};
+		req.nlh.nlmsg_len += RTA_LENGTH(sizeof(proto));
+	}
+
 	struct msghdr msg = {
 		.msg_name = &nladdr,
 		.msg_namelen = sizeof(nladdr),
@@ -158,7 +159,7 @@ static void print_info_msg(struct mptcp_info *info)
 	printf("bytes_acked:      %llu\n", info->mptcpi_bytes_acked);
 }
 
-static void parse_nlmsg(struct nlmsghdr *nlh)
+static void parse_nlmsg(struct nlmsghdr *nlh, __u32 proto)
 {
 	struct inet_diag_msg *r = NLMSG_DATA(nlh);
 	struct rtattr *tb[INET_DIAG_MAX + 1];
@@ -167,7 +168,7 @@ static void parse_nlmsg(struct nlmsghdr *nlh)
 			   nlh->nlmsg_len - NLMSG_LENGTH(sizeof(*r)),
 			   NLA_F_NESTED);
 
-	if (tb[INET_DIAG_INFO]) {
+	if (proto == IPPROTO_MPTCP && tb[INET_DIAG_INFO]) {
 		int len = RTA_PAYLOAD(tb[INET_DIAG_INFO]);
 		struct mptcp_info *info;
 
@@ -183,7 +184,7 @@ static void parse_nlmsg(struct nlmsghdr *nlh)
 	}
 }
 
-static void recv_nlmsg(int fd)
+static void recv_nlmsg(int fd, __u32 proto)
 {
 	char rcv_buff[8192];
 	struct nlmsghdr *nlh = (struct nlmsghdr *)rcv_buff;
@@ -216,7 +217,7 @@ static void recv_nlmsg(int fd)
 			       -(err->error), strerror(-(err->error)));
 			break;
 		}
-		parse_nlmsg(nlh);
+		parse_nlmsg(nlh, proto);
 		nlh = NLMSG_NEXT(nlh, len);
 	}
 }
@@ -230,14 +231,15 @@ static void get_mptcpinfo(__u32 token)
 		.idiag_ext              = 1 << (INET_DIAG_INFO - 1),
 		.id.idiag_cookie[0]     = token,
 	};
+	__u32 proto = IPPROTO_MPTCP;
 	int fd;
 
 	fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_SOCK_DIAG);
 	if (fd < 0)
 		die_perror("Netlink socket");
 
-	send_query(fd, &r);
-	recv_nlmsg(fd);
+	send_query(fd, &r, proto);
+	recv_nlmsg(fd, proto);
 
 	close(fd);
 }

-- 
2.48.1