[PATCH v8 0/8] pcapng: fixes and improvements

Stephen Hemminger
2026-02-16T21:43:19Z

Fix string handling in the pcapng library and improve test coverage.

The pcapng format uses 16-bit length fields for option data, but the
library did not validate input lengths and used fixed-size stack
buffers that could overflow with large strings.

Patches 1-4 add string validation, dynamic allocation, and return
value documentation. Existing return value conventions are preserved
to avoid an ABI break.

Patch 5 chains an additional mbuf segment when a comment exceeds
tailroom instead of dropping the packet.

Patch 6 replaces per-packet timestamp divisions with a precomputed
reciprocal multiply-shift.

Patches 7-8 improve test coverage and fix the build dependency on
the null PMD.

v8:
- Split patches for clarity (typo, Doxygen, validation, malloc)
- Preserve existing API/ABI — no error return changes
- Drop dumpcap patch (no API change to handle)
- Truncate overlong comments via strnlen on fast path
- Defer port_index update until after successful write

v7:
- Add meson build fix for disabled null PMD
- Add dumpcap error reporting improvements

Stephen Hemminger (8):
pcapng: correct typo in comment
pcapng: document return values
pcapng: add length checks to string arguments
pcapng: use malloc instead of fixed buffer size
pcapng: chain additional mbuf when comment exceeds tailroom
pcapng: improve performance of timestamping
test/pcapng: skip test if null driver missing
test/pcapng: add tests for comments

app/test/meson.build | 2 +-
app/test/test_pcapng.c | 154 +++++++++++++-----
doc/guides/rel_notes/release_26_03.rst | 5 +
lib/pcapng/rte_pcapng.c | 207 +++++++++++++++++++------
lib/pcapng/rte_pcapng.h | 13 +-
5 files changed, 288 insertions(+), 93 deletions(-)

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2.51.0