On 2026/6/13 0:13, Stephen Hemminger wrote:
On Fri, 12 Jun 2026 17:12:17 +0800
Xingui Yang <[email protected]> wrote:
Add a new padding mode to the txonly forwarding engine, which allows
sending packets with configurable small sizes without standard L2/L3
headers. This is useful for testing NIC padding logic.
When padding mode is enabled via --tx-pkt-pad-mode flag:
- l2_len and l3_len are set to 0 instead of standard header lengths
- Packet data is filled with a static pattern instead of
Ethernet/IP/UDP headers
- Minimum packet length validation is bypassed to allow small
packet sizes (e.g., set txpkts 14)
Signed-off-by: Xingui Yang <[email protected]>
Signed-off-by: Huisong Li <[email protected]>
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v2: Fix compilation exception of unterminated-string-initialization
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What about something like this (*not tested*) patch.
Hi Stephen,
Thank you for the valuable suggestion! Your approach is cleaner and
more elegant for generating runt frames with truncated headers.
However, our use case requires sending packets smaller than the
Ethernet header size (e.g., `set txpkts 9` or `set txpkts 2`).
These ultra-small packets are needed to test NIC padding logic where
no standard L2/L3 headers are present at all.
We could combine both approaches:
- Allow packet lengths down to 1 byte (remove the 14-byte minimum)
- Dynamically compute l2_len/l3_len based on actual packet length
- Use a fill pattern for packets too small to hold Ethernet header
- Keep the checksum offload handling from your patch
This way testpmd can support the full range:
- Normal packets (>= 14 + 20 + 8 bytes): full headers with checksum
- Runt frames (14-42 bytes): truncated headers, checksums disabled
- Ultra-small packets (<14 bytes): fill pattern only, l2_len/l3_len = 0
Would this combined approach be acceptable? We can submit a v3 patch
incorporating your suggestions plus support for ultra-small packets.
Thanks,
Xingui Yang
