Server: Implement `prefer_tcp` according to spec

2 files changed, 20 insertions, 14 deletions

diff --git a/internal/server/api.go b/internal/server/api.go
index 4648a8f..0c1a0f5 100644
--- a/internal/server/api.go
+++ b/internal/server/api.go
@@ -131,10 +131,19 @@ func APIInfo(server Server) error {
 	return nil
 }
 
+// see https://github.com/eduvpn/documentation/blob/v3/API.md#request-1
+func GetPreferTCPString(preferTCP bool) string {
+	if preferTCP {
+		return "yes"
+	}
+	return "no"
+}
+
 func APIConnectWireguard(
 	server Server,
 	profile_id string,
 	pubkey string,
+	preferTCP bool,
 	supportsOpenVPN bool,
 ) (string, string, time.Time, error) {
 	errorMessage := "failed obtaining a WireGuard configuration"
@@ -143,6 +152,8 @@ func APIConnectWireguard(
 		"accept":       {"application/x-wireguard-profile"},
 	}
 
+	// This profile also supports OpenVPN
+	// Indicate that we also accept OpenVPN profiles
 	if supportsOpenVPN {
 		headers.Add("accept", "application/x-openvpn-profile")
 	}
@@ -150,6 +161,7 @@ func APIConnectWireguard(
 	urlForm := url.Values{
 		"profile_id": {profile_id},
 		"public_key": {pubkey},
+		"prefer_tcp": {GetPreferTCPString(preferTCP)},
 	}
 	header, connectBody, connectErr := apiAuthorizedRetry(
 		server,
@@ -180,7 +192,7 @@ func APIConnectWireguard(
 	return string(connectBody), content, pTime, nil
 }
 
-func APIConnectOpenVPN(server Server, profile_id string) (string, time.Time, error) {
+func APIConnectOpenVPN(server Server, profile_id string, preferTCP bool) (string, time.Time, error) {
 	errorMessage := "failed obtaining an OpenVPN configuration"
 	headers := http.Header{
 		"content-type": {"application/x-www-form-urlencoded"},
@@ -189,6 +201,7 @@ func APIConnectOpenVPN(server Server, profile_id string) (string, time.Time, err
 
 	urlForm := url.Values{
 		"profile_id": {profile_id},
+		"prefer_tcp": {GetPreferTCPString(preferTCP)},
 	}
 
 	header, connectBody, connectErr := apiAuthorizedRetry(
diff --git a/internal/server/common.go b/internal/server/common.go
index 36dba32..6f57c7f 100644
--- a/internal/server/common.go
+++ b/internal/server/common.go
@@ -324,7 +324,7 @@ func getCurrentProfile(server Server) (*ServerProfile, error) {
 	}
 }
 
-func wireguardGetConfig(server Server, supportsOpenVPN bool) (string, string, error) {
+func wireguardGetConfig(server Server, preferTCP bool, supportsOpenVPN bool) (string, string, error) {
 	errorMessage := "failed getting server WireGuard configuration"
 	base, baseErr := server.GetBase()
 
@@ -344,6 +344,7 @@ func wireguardGetConfig(server Server, supportsOpenVPN bool) (string, string, er
 		server,
 		profile_id,
 		wireguardPublicKey,
+		preferTCP,
 		supportsOpenVPN,
 	)
 
@@ -366,7 +367,7 @@ func wireguardGetConfig(server Server, supportsOpenVPN bool) (string, string, er
 	return config, content, nil
 }
 
-func openVPNGetConfig(server Server) (string, string, error) {
+func openVPNGetConfig(server Server, preferTCP bool) (string, string, error) {
 	errorMessage := "failed getting server OpenVPN configuration"
 	base, baseErr := server.GetBase()
 
@@ -374,7 +375,7 @@ func openVPNGetConfig(server Server) (string, string, error) {
 		return "", "", &types.WrappedErrorMessage{Message: errorMessage, Err: baseErr}
 	}
 	profile_id := base.Profiles.Current
-	configOpenVPN, expires, configErr := APIConnectOpenVPN(server, profile_id)
+	configOpenVPN, expires, configErr := APIConnectOpenVPN(server, profile_id, preferTCP)
 
 	// Store start and end time
 	base.StartTime = util.GetCurrentTime()
@@ -433,14 +434,6 @@ func GetConfig(server Server, preferTCP bool) (string, string, error) {
 	supportsOpenVPN := profile.supportsOpenVPN()
 	supportsWireguard := profile.supportsWireguard()
 
-	// If preferTCP we must be able to get a config with OpenVPN
-	if preferTCP && supportsOpenVPN {
-		return "", "", &types.WrappedErrorMessage{
-			Message: errorMessage,
-			Err:     &ServerGetConfigForceTCPError{},
-		}
-	}
-
 	var config string
 	var configType string
 	var configErr error
@@ -448,9 +441,9 @@ func GetConfig(server Server, preferTCP bool) (string, string, error) {
 	if supportsWireguard {
 		// A wireguard connect call needs to generate a wireguard key and add it to the config
 		// Also the server could send back an OpenVPN config if it supports OpenVPN
-		config, configType, configErr = wireguardGetConfig(server, supportsOpenVPN)
+		config, configType, configErr = wireguardGetConfig(server, preferTCP, supportsOpenVPN)
 	} else {
-		config, configType, configErr = openVPNGetConfig(server)
+		config, configType, configErr = openVPNGetConfig(server, preferTCP)
 	}
 
 	if configErr != nil {