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net/netmon, wgengine/userspace: purge ChangeDelta.Major and address TODOs (#17823)

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updates tailscale/corp#33891

Addresses several older the TODO's in netmon.  This removes the 
Major flag precomputes the ChangeDelta state, rather than making
consumers of ChangeDeltas sort that out themselves.   We're also seeing
a lot of ChangeDelta's being flagged as "Major" when they are
not interesting, triggering rebinds in wgengine that are not needed.  This
cleans that up and adds a host of additional tests.

The dependencies are cleaned, notably removing dependency on netmon
itself for calculating what is interesting, and what is not.  This includes letting
individual platforms set a bespoke global "IsInterestingInterface"
function.  This is only used on Darwin.

RebindRequired now roughly follows how "Major" was historically
calculated but includes some additional checks for various
uninteresting events such as changes in interface addresses that
shouldn't trigger a rebind.  This significantly reduces thrashing (by
roughly half on Darwin clients which switching between nics).   The individual
values that we roll  into RebindRequired are also exposed so that
components consuming netmap.ChangeDelta can ask more
targeted questions.

Signed-off-by: Jonathan Nobels <jonathan@tailscale.com>
This commit is contained in:
Jonathan Nobels
2025-12-17 12:32:40 -05:00
committed by GitHub
parent 0fd1670a59
commit 3e89068792
19 changed files with 754 additions and 273 deletions
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net/netmon/netmon_darwin.go
+17 -4
View File
@@ -16,6 +16,12 @@ import (
"tailscale.com/util/eventbus"
)
func init() {
IsInterestingInterface = func(iface Interface, prefixes []netip.Prefix) bool {
return isInterestingInterface(iface.Name)
}
}
const debugRouteMessages = false
// unspecifiedMessage is a minimal message implementation that should not
@@ -125,11 +131,10 @@ func addrType(addrs []route.Addr, rtaxType int) route.Addr {
return nil
}
func (m *darwinRouteMon) IsInterestingInterface(iface string) bool {
func isInterestingInterface(iface string) bool {
baseName := strings.TrimRight(iface, "0123456789")
switch baseName {
// TODO(maisem): figure out what this list should actually be.
case "llw", "awdl", "ipsec":
case "llw", "awdl", "ipsec", "gif", "XHC", "anpi", "lo", "utun":
return false
}
return true
@@ -137,7 +142,7 @@ func (m *darwinRouteMon) IsInterestingInterface(iface string) bool {
func (m *darwinRouteMon) skipInterfaceAddrMessage(msg *route.InterfaceAddrMessage) bool {
if la, ok := addrType(msg.Addrs, unix.RTAX_IFP).(*route.LinkAddr); ok {
if !m.IsInterestingInterface(la.Name) {
if !isInterestingInterface(la.Name) {
return true
}
}
@@ -150,6 +155,14 @@ func (m *darwinRouteMon) skipRouteMessage(msg *route.RouteMessage) bool {
// dst = fe80::b476:66ff:fe30:c8f6%15
return true
}
// We can skip route messages from uninteresting interfaces. We do this upstream
// against the InterfaceMonitor, but skipping them here avoids unnecessary work.
if la, ok := addrType(msg.Addrs, unix.RTAX_IFP).(*route.LinkAddr); ok {
if !isInterestingInterface(la.Name) {
return true
}
}
return false
}