[PATCH bpf-next] selftests/bpf: Sanitize traffic monitor log file names

[Vineet Gupta <vineet.gupta@linux.dev>]

The traffic monitor names its capture logs after the test and subtest
being run, replacing '/' and ' ' so the result is usable as a file name.
Test names are free form though, and other characters make it through.
A subtest called "INET4: bpf timestamping" produces

  /tmp/tmon_pcap/packets-125-15-net_timestamping__INET4:_bpf_timestamping-net_timestamping_ns.log

CI systems that collect these logs as artifacts reject such names.
GitHub Actions' upload-artifact fails the upload with

  Error: The path for one of the files in artifact is not valid:
  ... Contains the following character:  Colon :

Replace the whole set of awkward characters in one pass rather than
adding another strchr() loop per character. Note the loop tests *p
before calling strchr(), so the terminating NUL is never passed to it.

This came up as a side error/annoyance when trying to re-enable BPF-GCC
CI runs [1]. The CI side already has path name normalization and needs
some tweaking as well, however fixing it at the source also makes sense.

Fixes: f52403b6bfea ("selftests/bpf: Add traffic monitor functions.")
Link: https://github.com/kernel-patches/vmtest/actions/runs/30710914503/job/91399011388 [1]
Signed-off-by: Vineet Gupta <vineet.gupta@linux.dev>
---
 tools/testing/selftests/bpf/network_helpers.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/bpf/network_helpers.c b/tools/testing/selftests/bpf/network_helpers.c
index db935a9d9fc1..3818cec354a0 100644
--- a/tools/testing/selftests/bpf/network_helpers.c
+++ b/tools/testing/selftests/bpf/network_helpers.c
@@ -1142,10 +1142,13 @@ static void encode_test_name(char *buf, size_t len, const char *test_name, const
 		snprintf(buf, len, "%s__%s", test_name, subtest_name);
 	else
 		snprintf(buf, len, "%s", test_name);
-	while ((p = strchr(buf, '/')))
-		*p = '_';
-	while ((p = strchr(buf, ' ')))
-		*p = '_';
+	/* Test names are free form, so replace anything that is awkward in a
+	 * file name. Besides the path separator, this covers the characters
+	 * rejected by CI systems collecting these logs as artifacts.
+	 */
+	for (p = buf; *p; p++)
+		if (strchr("/ \":<>|*?\r\n", *p))
+			*p = '_';
 }
 
 #define PCAP_DIR "/tmp/tmon_pcap"
-- 
2.55.0