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suricata/doc/userguide/capture-hardware
Lukas Sismis ed47bf5dd8 dpdk: handle segmented mbufs in copy modes
Packets received in segmented mbufs that cannot be linearized are
inspected as a copy. In the copy modes (IPS/TAP), modifications made to
the copy (inline stream normalization, the replace keyword) did not
reach the mbufs, so the unmodified packet was forwarded. Chains larger
than the maximum packet size were truncated for inspection but
forwarded in full, and chains that could not be copied were forwarded
uninspected.

When Suricata modifies a copied packet, it now writes the data back to
the mbuf chain before transmitting it. Chains that cannot be inspected
in full or transmitted are dropped: chains larger than the maximum
packet size, chains with more segments than the copy interface can
transmit, and malformed chains.

Forwarding chains requires the multi-segment TX offload, which replaces
MBUF_FAST_FREE and selects a slower TX path on some NICs. As mbufs sized
from the MTU rarely lead to chains on physical NICs, forwarding them is
opt-in through the new tx-segmented-mbufs interface setting (default
false), which both copy interfaces must share. Without it, chains that
cannot be linearized are dropped in the copy modes.

The drops are counted in capture.dpdk.segmented_drops and
capture.dpdk.segmented_too_large. In IPS mode, they are also counted in
ips.blocked with the new capture_error drop reason, so that the drop
reasons explain the blocked packets.

Ticket: 6012
6 days ago
..
af-packet.rst af-packet: disable hwtimestamp by default 11 months ago
af-xdp.rst doc: document AF_XDP feature 4 years ago
dpdk.rst dpdk: handle segmented mbufs in copy modes 6 days ago
ebpf-xdp.rst doc: minor ebpf doc update for fedora/rhel 5 months ago
endace-dag.rst doc: Improve grammar, spelling and clarifications 6 years ago
index.rst doc/af-packet: document disable-hwtimestamp option 11 months ago
myricom.rst doc: Improve grammar, spelling and clarifications 6 years ago
napatech.rst napatech: update docs to remove hba reference 3 years ago
netmap.rst doc/userguide: spelling 4 years ago
pcap-file.rst pcap-file: skip setvbuf on non-seekable streams 5 months ago