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derp, wgengine: let clients advertise an opaque app name to DERP servers

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Add an AppName field to the DERP ClientInfo so DERP servers can
attribute connections to the application making them, primarily for
best effort stats purposes. The value is plumbed per engine instance
rather than via a process global, so a process hosting multiple stacks
can attribute each one's DERP connections separately:
wgengine.Config.DERPAppName flows through magicsock.Options and
derphttp.Client into the naclbox-sealed ClientInfo JSON. Old servers
ignore the unknown field.

There are no callers in the tree yet setting the name.

Updates tailscale/corp#24454

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Change-Id: Ia7d3e9c2b6f8140e5a9d7c3b2e6f1a8d4c0b5e9f
This commit is contained in:
Brad Fitzpatrick
2026-07-20 07:33:44 -07:00
committed by Brad Fitzpatrick
parent 37e175a032
commit 246c82a658
8 changed files with 161 additions and 1 deletions
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derp/derp_client.go
+16 -1
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@@ -33,6 +33,7 @@ type Client struct {
meshKey key.DERPMesh
canAckPings bool
isProber bool
appName string
wmu sync.Mutex // hold while writing to bw
bw *bufio.Writer
@@ -60,6 +61,7 @@ type clientOpt struct {
ServerPub key.NodePublic
CanAckPings bool
IsProber bool
AppName string
}
// MeshKey returns a ClientOpt to pass to the DERP server during connect to get
@@ -84,6 +86,13 @@ func CanAckPings(v bool) ClientOpt {
return clientOptFunc(func(o *clientOpt) { o.CanAckPings = v })
}
// AppName returns a ClientOpt to set an opaque app name string to
// advertise to the DERP server for stats purposes. It is sent to the
// server in the ClientInfo.
func AppName(name string) ClientOpt {
return clientOptFunc(func(o *clientOpt) { o.AppName = name })
}
func NewClient(privateKey key.NodePrivate, nc Conn, brw *bufio.ReadWriter, logf logger.Logf, opts ...ClientOpt) (*Client, error) {
var opt clientOpt
for _, o := range opts {
@@ -106,6 +115,7 @@ func newClient(privateKey key.NodePrivate, nc Conn, brw *bufio.ReadWriter, logf
meshKey: opt.MeshKey,
canAckPings: opt.CanAckPings,
isProber: opt.IsProber,
appName: opt.AppName,
clock: tstime.StdClock{},
}
if opt.ServerPub.IsZero() {
@@ -179,6 +189,10 @@ type ClientInfo struct {
// IsProber is whether this client is a prober.
IsProber bool `json:",omitempty"`
// AppName is an optional opaque app name string the client
// advertises to the server for stats purposes.
AppName string `json:",omitempty"`
}
// Equal reports if two clientInfo values are equal.
@@ -186,7 +200,7 @@ func (c *ClientInfo) Equal(other *ClientInfo) bool {
if c == nil || other == nil {
return c == other
}
if c.Version != other.Version || c.CanAckPings != other.CanAckPings || c.IsProber != other.IsProber {
if c.Version != other.Version || c.CanAckPings != other.CanAckPings || c.IsProber != other.IsProber || c.AppName != other.AppName {
return false
}
return c.MeshKey.Equal(other.MeshKey)
@@ -198,6 +212,7 @@ func (c *Client) sendClientKey() error {
MeshKey: c.meshKey,
CanAckPings: c.canAckPings,
IsProber: c.isProber,
AppName: c.appName,
})
if err != nil {
return err