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wgengine/wgcfg: only write peer headers if necessary (#5449) 

On sufficiently large tailnets, even writing the peer header (~95 bytes)
can result in a large amount of data that needs to be serialized and
deserialized. Only write headers for peers that need to have their
configuration changed.

Signed-off-by: Andrew Dunham <andrew@tailscale.com>
This commit is contained in:
Andrew Dunham 2022-08-29 20:47:52 -04:00 committed by GitHub
parent 81dba3738e
commit d6c3588ed3
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GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 28 additions and 5 deletions
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33
wgengine/wgcfg/writer.go
View File

@ -16,8 +16,11 @@ import (
// ToUAPI writes cfg in UAPI format to w.
// Prev is the previous device Config.
// Prev is required so that we can remove now-defunct peers
// without having to remove and re-add all peers.
//
// Prev is required so that we can remove now-defunct peers without having to
// remove and re-add all peers, and so that we can avoid writing information
// about peers that have not changed since the previous time we wrote our
// Config.
func (cfg *Config) ToUAPI(logf logger.Logf, w io.Writer, prev *Config) error {
var stickyErr error
set := func(key, value string) {
@ -49,13 +52,33 @@ func (cfg *Config) ToUAPI(logf logger.Logf, w io.Writer, prev *Config) error {
// Add/configure all new peers.
for _, p := range cfg.Peers {
oldPeer, wasPresent := old[p.PublicKey]
// We only want to write the peer header/version if we're about
// to change something about that peer, or if it's a new peer.
// Figure out up-front whether we'll need to do anything for
// this peer, and skip doing anything if not.
//
// If the peer was not present in the previous config, this
// implies that this is a new peer; set all of these to 'true'
// to ensure that we're writing the full peer configuration.
willSetEndpoint := oldPeer.WGEndpoint != p.PublicKey || !wasPresent
willChangeIPs := !cidrsEqual(oldPeer.AllowedIPs, p.AllowedIPs) || !wasPresent
willChangeKeepalive := oldPeer.PersistentKeepalive != p.PersistentKeepalive || !wasPresent
if !willSetEndpoint && !willChangeIPs && !willChangeKeepalive {
// It's safe to skip doing anything here; wireguard-go
// will not remove a peer if it's unspecified unless we
// tell it to (which we do below if necessary).
continue
}
setPeer(p)
set("protocol_version", "1")
// Avoid setting endpoints if the correct one is already known
// to WireGuard, because doing so generates a bit more work in
// calling magicsock's ParseEndpoint for effectively a no-op.
if oldPeer.WGEndpoint != p.PublicKey {
if willSetEndpoint {
if wasPresent {
// We had an endpoint, and it was wrong.
// By construction, this should not happen.
@ -72,7 +95,7 @@ func (cfg *Config) ToUAPI(logf logger.Logf, w io.Writer, prev *Config) error {
// If p.AllowedIPs is a strict superset of oldPeer.AllowedIPs,
// then skip replace_allowed_ips and instead add only
// the new ipps with allowed_ip.
if !cidrsEqual(oldPeer.AllowedIPs, p.AllowedIPs) {
if willChangeIPs {
set("replace_allowed_ips", "true")
for _, ipp := range p.AllowedIPs {
set("allowed_ip", ipp.String())
@ -81,7 +104,7 @@ func (cfg *Config) ToUAPI(logf logger.Logf, w io.Writer, prev *Config) error {
// Set PersistentKeepalive after the peer is otherwise configured,
// because it can trigger handshake packets.
if oldPeer.PersistentKeepalive != p.PersistentKeepalive {
if willChangeKeepalive {
setUint16("persistent_keepalive_interval", p.PersistentKeepalive)
}
}