From: Geliang Tang <tanggeliang@kylinos.cn>

In mptcp_connect.c, strchr() returns a pointer to a character within
the input string, which is declared as const char *. Assigning this
return value to a non-const char * discards the const qualifier,
triggering compiler warnings:

 make: Entering directory 'tools/testing/selftests/net/mptcp'
   CC       mptcp_connect
 mptcp_connect.c: In function 'parse_cmsg_types':
 mptcp_connect.c:1267:22: warning: initialization discards 'const'
	qualifier from pointer target type [-Wdiscarded-qualifiers]
  1267 |         char *next = strchr(type, ',');
       |                      ^~~~~~
 mptcp_connect.c: In function 'parse_setsock_options':
 mptcp_connect.c:1295:22: warning: initialization discards 'const'
	qualifier from pointer target type [-Wdiscarded-qualifiers]
  1295 |         char *next = strchr(name, ',');
       |                      ^~~~~~
 make: Leaving directory 'tools/testing/selftests/net/mptcp'

Fix these warnings by declaring the 'next' variable as const char *,
as it is only used for read-only parsing.

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
---
 tools/testing/selftests/net/mptcp/mptcp_connect.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/net/mptcp/mptcp_connect.c b/tools/testing/selftests/net/mptcp/mptcp_connect.c
index cbe573c4ab3a..ea4cb6c1bd5e 100644
--- a/tools/testing/selftests/net/mptcp/mptcp_connect.c
+++ b/tools/testing/selftests/net/mptcp/mptcp_connect.c
@@ -1264,7 +1264,7 @@ static void apply_cmsg_types(int fd, const struct cfg_cmsg_types *cmsg)
 
 static void parse_cmsg_types(const char *type)
 {
-	char *next = strchr(type, ',');
+	const char *next = strchr(type, ',');
 	unsigned int len = 0;
 
 	cfg_cmsg_types.cmsg_enabled = 1;
@@ -1292,7 +1292,7 @@ static void parse_cmsg_types(const char *type)
 
 static void parse_setsock_options(const char *name)
 {
-	char *next = strchr(name, ',');
+	const char *next = strchr(name, ',');
 	unsigned int len = 0;
 
 	if (next) {
-- 
2.53.0

Hi Geliang,

On 20/06/2026 01:32, Geliang Tang wrote:
> From: Geliang Tang <tanggeliang@kylinos.cn>
> 
> In mptcp_connect.c, strchr() returns a pointer to a character within
> the input string, which is declared as const char *. Assigning this
> return value to a non-const char * discards the const qualifier,
> triggering compiler warnings:
> 
>  make: Entering directory 'tools/testing/selftests/net/mptcp'
>    CC       mptcp_connect
>  mptcp_connect.c: In function 'parse_cmsg_types':
>  mptcp_connect.c:1267:22: warning: initialization discards 'const'
> 	qualifier from pointer target type [-Wdiscarded-qualifiers]
>   1267 |         char *next = strchr(type, ',');
>        |                      ^~~~~~
>  mptcp_connect.c: In function 'parse_setsock_options':
>  mptcp_connect.c:1295:22: warning: initialization discards 'const'
> 	qualifier from pointer target type [-Wdiscarded-qualifiers]
>   1295 |         char *next = strchr(name, ',');
>        |                      ^~~~~~
>  make: Leaving directory 'tools/testing/selftests/net/mptcp'
> 
> Fix these warnings by declaring the 'next' variable as const char *,
> as it is only used for read-only parsing.
Thanks!

Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>

New patches for t/upstream:
- 7fb42c115a57: selftests: mptcp: fix const qualifier warnings in strchr
usage
- Results: 7fc976a6891c..23524644cc06 (export)

Tests are now in progress:

- export:
https://github.com/multipath-tcp/mptcp_net-next/commit/83be48a0589e16868a5c7e58173046507a3084d1/checks

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.

Hi Geliang,

Thank you for your modifications, that's great!

Our CI did some validations and here is its report:

- KVM Validation: normal (except selftest_mptcp_join): Success! ✅
- KVM Validation: normal (only selftest_mptcp_join): Success! ✅
- KVM Validation: debug (except selftest_mptcp_join): Notice: Call Traces at boot time, rebooted and continued ⚠️ 
- KVM Validation: debug (only selftest_mptcp_join): Notice: Call Traces at boot time, rebooted and continued ⚠️ 
- KVM Validation: btf-normal (only bpftest_all): Success! ✅
- KVM Validation: btf-debug (only bpftest_all): Notice: Call Traces at boot time, rebooted and continued ⚠️ 
- Task: https://github.com/multipath-tcp/mptcp_net-next/actions/runs/27853696726

Initiator: Patchew Applier
Commits: https://github.com/multipath-tcp/mptcp_net-next/commits/5b68cf5259c8
Patchwork: https://patchwork.kernel.org/project/mptcp/list/?series=1114094


If there are some issues, you can reproduce them using the same environment as
the one used by the CI thanks to a docker image, e.g.:

    $ cd [kernel source code]
    $ docker run -v "${PWD}:${PWD}:rw" -w "${PWD}" --privileged --rm -it \
        --pull always mptcp/mptcp-upstream-virtme-docker:latest \
        auto-normal

For more details:

    https://github.com/multipath-tcp/mptcp-upstream-virtme-docker


Please note that despite all the efforts that have been already done to have a
stable tests suite when executed on a public CI like here, it is possible some
reported issues are not due to your modifications. Still, do not hesitate to
help us improve that ;-)

Cheers,
MPTCP GH Action bot
Bot operated by Matthieu Baerts (NGI0 Core)