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derp/derphttp: determine whether a region connect was to non-ideal node 

... and then do approximately nothing with that information, other
than a big TODO. This is mostly me relearning this code and leaving
breadcrumbs for others in the future.

Updates #12724

Signed-off-by: Brad Fitzpatrick <brad@danga.com>
This commit is contained in:
Brad Fitzpatrick 2024-07-06 21:46:33 -07:00 committed by Brad Fitzpatrick
parent 0b32adf9ec
commit f77821fd63
1 changed files with 14 additions and 0 deletions
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14
derp/derphttp/derphttp_client.go
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@ -381,6 +381,7 @@ func (c *Client) connect(ctx context.Context, caller string) (client *derp.Clien
}()
var node *tailcfg.DERPNode // nil when using c.url to dial
var idealNodeInRegion bool
switch {
case useWebsockets():
var urlStr string
@ -421,6 +422,7 @@ func (c *Client) connect(ctx context.Context, caller string) (client *derp.Clien
default:
c.logf("%s: connecting to derp-%d (%v)", caller, reg.RegionID, reg.RegionCode)
tcpConn, node, err = c.dialRegion(ctx, reg)
idealNodeInRegion = err == nil && reg.Nodes[0] == node
}
if err != nil {
return nil, 0, err
@ -494,6 +496,18 @@ func (c *Client) connect(ctx context.Context, caller string) (client *derp.Clien
}
req.Header.Set("Upgrade", "DERP")
req.Header.Set("Connection", "Upgrade")
if !idealNodeInRegion && reg != nil {
// This is purely informative for now (2024-07-06) for stats:
req.Header.Set("Ideal-Node", reg.Nodes[0].Name)
// TODO(bradfitz,raggi): start a time.AfterFunc for 30m-1h or so to
// dialNode(reg.Nodes[0]) and see if we can even TCP connect to it. If
// so, TLS handshake it as well (which is mixed up in this massive
// connect method) and then if it all appears good, grab the mutex, bump
// connGen, finish the Upgrade, close the old one, and set a new field
// on Client that's like "here's the connect result and connGen for the
// next connect that comes in"). Tracking bug for all this is:
// https://github.com/tailscale/tailscale/issues/12724
}
if !serverPub.IsZero() && serverProtoVersion != 0 {
// parseMetaCert found the server's public key (no TLS