From df274ad6ea68360749baa9b9bfe0a663d2804e65 Mon Sep 17 00:00:00 2001
From: Juliusz Chroboczek <jch@irif.fr>
Date: Mon, 30 Sep 2024 00:23:36 +0200
Subject: [PATCH] Split out SDP fragment parsing, add test.

---
 webserver/whip.go      | 30 ++++++++++++++++--------------
 webserver/whip_test.go | 35 +++++++++++++++++++++++++++++++++++
 2 files changed, 51 insertions(+), 14 deletions(-)
 create mode 100644 webserver/whip_test.go

diff --git a/webserver/whip.go b/webserver/whip.go
index 2838375..cf7d798 100644
--- a/webserver/whip.go
+++ b/webserver/whip.go
@@ -1,6 +1,7 @@
 package webserver
 
 import (
+	"bufio"
 	"bytes"
 	"crypto/aes"
 	"crypto/cipher"
@@ -345,23 +346,25 @@ func whipResourceHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	body, err := io.ReadAll(http.MaxBytesReader(w, r.Body, sdpLimit))
+	err = parseSDPFrag(
+		http.MaxBytesReader(w, r.Body, sdpLimit),
+		c.GotICECandidate,
+	)
 	if err != nil {
-		httpError(w, err)
+		log.Printf("WHIP trickle ICE: %v", err)
+		http.Error(w, "bad request", http.StatusBadRequest)
 		return
 	}
+	w.WriteHeader(http.StatusNoContent)
+}
 
-	if len(body) < 2 {
-		http.Error(w, "SDP truncated", http.StatusBadRequest)
-		return
-	}
-
-	// RFC 8840
-	lines := bytes.Split(body, []byte{'\n'})
+// RFC 8840
+func parseSDPFrag(r io.Reader, f func(webrtc.ICECandidateInit) error) error {
+	scanner := bufio.NewScanner(r)
 	mLineIndex := -1
 	var mid, ufrag []byte
-	for _, l := range lines {
-		l = bytes.TrimRight(l, " \r")
+	for scanner.Scan() {
+		l := scanner.Bytes()
 		if bytes.HasPrefix(l, []byte("a=ice-ufrag:")) {
 			ufrag = l[len("a=ice-ufrag:"):]
 		} else if bytes.HasPrefix(l, []byte("m=")) {
@@ -385,12 +388,11 @@ func whipResourceHandler(w http.ResponseWriter, r *http.Request) {
 				s := string(ufrag)
 				init.UsernameFragment = &s
 			}
-			err := c.GotICECandidate(init)
+			err := f(init)
 			if err != nil {
 				log.Printf("WHIP candidate: %v", err)
 			}
 		}
 	}
-	w.WriteHeader(http.StatusNoContent)
-	return
+	return nil
 }
diff --git a/webserver/whip_test.go b/webserver/whip_test.go
new file mode 100644
index 0000000..7fb03f7
--- /dev/null
+++ b/webserver/whip_test.go
@@ -0,0 +1,35 @@
+package webserver
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/pion/webrtc/v3"
+)
+
+func TestParseSDPFrag(t *testing.T) {
+	sdp := `a=ice-ufrag:FZ0m
+a=ice-pwd:NRT+gj1EhsEwMm9MA7ljzBRy
+m=audio 9 UDP/TLS/RTP/SAVPF 0
+a=mid:0
+a=candidate:2930517337 1 udp 2113937151 1eaafdf1-4127-499f-90d4-8c35ea49d5e6.local 44360 typ host generation 0 ufrag FZ0m network-cost 999
+2024/09/30 00:07:41 {candidate:2930517337 1 udp 2113937151 1eaafdf1-4127-499f-90d4-8c35ea49d5e6.local 44360 typ host generation 0 ufrag FZ0m network-cost 999 0xc00062a580 0xc000620288 0xc00062a590}
+a=end-of-candidates`
+	r := strings.NewReader(sdp)
+	candidates := []webrtc.ICECandidateInit(nil)
+	err := parseSDPFrag(r, func(c webrtc.ICECandidateInit) error {
+		candidates = append(candidates, c)
+		return nil
+	})
+	if err != nil {
+		t.Errorf("parseSDPFrag: %v", err)
+	}
+	if len(candidates) != 1 {
+		t.Errorf("Expected 1, got %v", candidates)
+	}
+	if *candidates[0].SDPMLineIndex != 0 ||
+		*candidates[0].SDPMid != "0" ||
+		*candidates[0].UsernameFragment != "FZ0m" {
+		t.Errorf("Got %v", candidates[0])
+	}
+}