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Support MSC4040 SRV lookups (#411)
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turt2live and devonh authored Aug 22, 2023
1 parent e5cb0de commit 740f742
Showing 1 changed file with 22 additions and 1 deletion.
23 changes: 22 additions & 1 deletion fclient/resolve.go
Original file line number Diff line number Diff line change
Expand Up @@ -108,7 +108,7 @@ func resolveServer(ctx context.Context, serverName spec.ServerName, checkWellKno
// well as 3.3 and 3.4)
func handleNoWellKnown(ctx context.Context, serverName spec.ServerName) (results []ResolutionResult) {
// 4. If the /.well-known request resulted in an error response
_, records, err := net.DefaultResolver.LookupSRV(ctx, "matrix", "tcp", string(serverName))
records, err := lookupSRV(ctx, serverName)
if err == nil && len(records) > 0 {
for _, rec := range records {
// If the domain is a FQDN, remove the trailing dot at the end. This
Expand Down Expand Up @@ -142,3 +142,24 @@ func handleNoWellKnown(ctx context.Context, serverName spec.ServerName) (results

return
}

func lookupSRV(ctx context.Context, serverName spec.ServerName) ([]*net.SRV, error) {
// Check matrix-fed service first, as of Matrix 1.8
_, records, err := net.DefaultResolver.LookupSRV(ctx, "matrix-fed", "tcp", string(serverName))
if err != nil {
if dnserr, ok := err.(*net.DNSError); ok {
if !dnserr.IsNotFound {
// not found errors are expected, but everything else is very much not
return records, err
}
} else {
return records, err
}
} else {
return records, nil // we got a hit on the matrix-fed service, so use that
}

// we didn't get a hit on matrix-fed, so try deprecated matrix service
_, records, err = net.DefaultResolver.LookupSRV(ctx, "matrix", "tcp", string(serverName))
return records, err // we don't need to process this here
}

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