[dhcp4relay] Reject first-hop requests with relay information#124
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[dhcp4relay] Reject first-hop requests with relay information#124Xichen96 wants to merge 2 commits into
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Drop untrusted first-hop requests that already carry Option 82 before assigning giaddr or appending relay information. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 2b881aa9-3a3a-4aaf-b2ca-b941705b2438 Signed-off-by: Xichen96 <lukelin0907@gmail.com>
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Walk DHCP options with cookie, length, PAD, and END validation so bytes after END cannot trigger the untrusted first-hop drop. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 2b881aa9-3a3a-4aaf-b2ca-b941705b2438 Signed-off-by: Xichen96 <lukelin0907@gmail.com>
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Description of PR
Summary:
Reject a zero-
giaddrDHCP request that already contains Option 82 before therelay assigns
giaddror appends another relay information option.This is a low-priority placeholder for a non-current deployment scenario. This
draft must not merge yet.
Type of change
Approach
What is the motivation for this PR?
SONiC has no trusted-circuit configuration. RFC 3046 safe untrusted behavior,
and the SONiC ISC relay default, require dropping a first-hop request that
already carries relay information. The native relay currently assigns
giaddrand appends a duplicate Option 82.
How did you do it?
giaddrclient requests.packet.
send_udpis not called,giaddrand hops remain unchanged, and no duplicate option is appended.
How did you verify/test it?
Focused native unit code is included but was NOT RUN, per explicit test
deferral. Test execution is deferred until the higher-priority DHCP relay PRs
listed below merge.
Any platform specific information?
None. This covers a lower-priority, non-current deployment scenario.
Dependencies and future validation TODOs
Validation sequencing depends on these higher-priority relay PRs merging first
(no code dependency; this branch is independently based on fresh
origin/master):Before marking ready or merging:
giaddrDHCP with apre-existing Option 82 and proves no packet reaches the upstream server:
[dhcp_relay] Cover first-hop requests with Option 82 sonic-mgmt#26322
Documentation
Behavior follows RFC 3046 untrusted-circuit handling and the SONiC ISC default.