From 398c0b485d75719f5abc5aefb2db89c84480e62b Mon Sep 17 00:00:00 2001
From: sukun <sukunrt@gmail.com>
Date: Wed, 12 Jun 2024 16:25:57 +0530
Subject: [PATCH] webrtc: fix ufrag prefix for dialing (#2832)

---
 p2p/transport/webrtc/transport.go      | 8 +++++---
 p2p/transport/webrtc/transport_test.go | 7 +++++++
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/p2p/transport/webrtc/transport.go b/p2p/transport/webrtc/transport.go
index b04753ecab..68a2988c78 100644
--- a/p2p/transport/webrtc/transport.go
+++ b/p2p/transport/webrtc/transport.go
@@ -415,15 +415,17 @@ func genUfrag() string {
 		uFragAlphabet = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890"
 		uFragPrefix   = "libp2p+webrtc+v1/"
 		uFragIdLength = 32
-		uFragIdOffset = len(uFragPrefix)
-		uFragLength   = uFragIdOffset + uFragIdLength
+		uFragLength   = len(uFragPrefix) + uFragIdLength
 	)
 
 	seed := [8]byte{}
 	rand.Read(seed[:])
 	r := mrand.New(mrand.NewSource(binary.BigEndian.Uint64(seed[:])))
 	b := make([]byte, uFragLength)
-	for i := uFragIdOffset; i < uFragLength; i++ {
+	for i := 0; i < len(uFragPrefix); i++ {
+		b[i] = uFragPrefix[i]
+	}
+	for i := len(uFragPrefix); i < uFragLength; i++ {
 		b[i] = uFragAlphabet[r.Intn(len(uFragAlphabet))]
 	}
 	return string(b)
diff --git a/p2p/transport/webrtc/transport_test.go b/p2p/transport/webrtc/transport_test.go
index a3054a82df..5831a257a7 100644
--- a/p2p/transport/webrtc/transport_test.go
+++ b/p2p/transport/webrtc/transport_test.go
@@ -860,3 +860,10 @@ func TestMaxInFlightRequests(t *testing.T) {
 	require.Equal(t, count, int(success.Load()), "expected exactly 3 dial successes")
 	require.Equal(t, 1, int(fails.Load()), "expected exactly 1 dial failure")
 }
+
+func TestGenUfrag(t *testing.T) {
+	for i := 0; i < 10; i++ {
+		s := genUfrag()
+		require.True(t, strings.HasPrefix(s, "libp2p+webrtc+v1/"))
+	}
+}