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ipn/ipnlocal: route extra WireGuard AllowedIPs through the route manager

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The conn25 extension's ExtraWireGuardAllowedIPs hook (Transit IPs)
was only appended to wgcfg.Config.Peers in authReconfig. Now that
outbound peer selection comes from the route manager's outbound
table via the engine's PeerByIPPacketFunc (which, when installed,
replaces wireguard-go's AllowedIPs trie lookup entirely) and lazily
created peers get their allowed IPs from the route manager via the
engine's peer config func, those extras never reached either path:
outbound packets to Transit IPs matched no peer, and lazily created
peers didn't accept inbound Transit IP sources.

Teach the route manager a per-peer set of extra allowed IPs, staged
by Mutation.SetExtraAllowedIPs. They appear in the outbound table
and in PeerAllowedIPs (so both outbound routing and per-peer allowed
source prefixes see them) but are excluded from the OS route set,
preserving the hook's contract that the extras reach WireGuard but
not the OS routing table. authReconfig now feeds the hook's results
into the route manager and incrementally syncs any changed peers to
the WireGuard device; the append to cfg.Peers remains only so Reconfig's
full per-peer device sync doesn't strip the extras from active
peers, and goes away with Config.Peers.

Updates #12542

Change-Id: I06c8fa30929fbf8fe171a2d34c47c6fcc3abfa16
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This commit is contained in:
Brad Fitzpatrick
2026-07-14 07:11:34 -07:00
committed by Brad Fitzpatrick
parent aff605d163
commit 6a635c4e55
3 changed files with 91 additions and 2 deletions
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ipn/ipnlocal/node_backend.go
+22
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@@ -938,6 +938,28 @@ func (nb *nodeBackend) updateRouteManagerPrefs(p routePrefs) (changedAllowedIPs
return res.AllowedIPs
}
// updateRouteManagerExtras pushes each peer's extra WireGuard-only
// allowed IPs into the route manager, obtained by calling fn (the
// [ipnext.Hooks.ExtraWireGuardAllowedIPs] hook) with each peer's
// public key.
//
// It returns the peers whose allowed source prefixes changed as a
// result, as described by [routemanager.Result.AllowedIPs].
func (nb *nodeBackend) updateRouteManagerExtras(fn func(key.NodePublic) views.Slice[netip.Prefix]) (changedAllowedIPs map[key.NodePublic][]netip.Prefix) {
nb.mu.Lock()
defer nb.mu.Unlock()
var extras map[tailcfg.NodeID][]netip.Prefix
for id, p := range nb.peers {
if pfxs := fn(p.Key()); pfxs.Len() > 0 {
mak.Set(&extras, id, pfxs.AsSlice())
}
}
rt := nb.routeMgr.Begin()
rt.SetExtraAllowedIPs(extras)
res := rt.Commit()
return res.AllowedIPs
}
// osRoutes returns the sorted set of prefixes that the route manager
// wants programmed into the OS routing table.
func (nb *nodeBackend) osRoutes() []netip.Prefix {