tcprewrite - fix adding vlan tag with missing options - #994
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fklassen merged 1 commit intoJul 17, 2026
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Fix an issue where using tcprewrite to add a vlan tag to untagged packets, and omitting either the --enet-vlan-cfi, or the --enet-vlan-pri option, the resulting pcap is truncated by 4 bytes (size of vlan header). This also changes the following so that the vlan tag value is manatory, but the priority and the format are optional: * Both options --enet-vlan-pri/--enet-vlan-cfi now explicitly default to 0 * Add a one-time warning if either option is missing, then proceed and use default * update the doc so that --enet-vlan-tag option is marked as mandatory when adding a vlan tag. Fixes: appneta#990 Assisted-by: Claude Opus 4.8 Signed-off-by: Gabriel Ganne <gabriel.ganne@gmail.com>
This was referenced Jul 17, 2026
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Fix an issue where using tcprewrite to add a vlan tag to untagged packets, and omitting either the
--enet-vlan-cfi, or the--enet-vlan-prioption, the resulting pcap is truncated by 4 bytes (size of vlan header).This also changes the following so that the vlan tag value is manatory, but the priority and the format are optional:
--enet-vlan-pri/--enet-vlan-cfinow explicitly default to 0--enet-vlan-tagoption is marked as mandatory when adding a vlan tag.The conditions for the issue to happen are a tiny bit more narrow than in the linked issue: for example if the packet is already vlan-tagged, we're not taking the same branch and have no issue (eg. feed the output of the buggy tcprewrite command to itself). Because of this (and following LLM-assisted review advice) I added comments on the branch to explicit the else branches to make it clear this branch is already handled and a warning has been sent during option parsing.
Fixes: #990
Assisted-by: Claude Opus 4.8