oxidecomputer / oxidecomputer/maghemite

bestpath: Allow operator to choose whether MED is compared for BGP paths via differing peer ASNs

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bgp want
Dominant language
Rust
Stars
94
Forks
6
Avg merge
1d 8h
Merged PRs (30d)
12

Description

The current implementation of BGP bestpath always paths by neighboring ASN before comparing MED (per the BGP-4 RFC).
However, this prevents a BGP router from being able to consider two paths from different neighboring ASNs as multipath candidates at the same time.

It would be good to update our bestpath behavior to accommodate multipath across different neighboring ASNs, as that BGP design is not uncommon in enterprise DC deployments.

Contributor guide

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by locating the BGP bestpath implementation and the handling of MED, neighboring ASNs, and multipath candidates. Review the current behavior against the BGP-4 rule described in the issue, then determine the operator-facing choice needed. Done means paths from different neighboring ASNs can be considered for multipath when that option is enabled, while the existing behavior remains available.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
networking
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
30/100

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