From bfb889910af094042bd975b32a578b447bcc1e08 Mon Sep 17 00:00:00 2001
From: Nardi Ivan <nardi.ivan@gmail.com>
Date: Sat, 19 Dec 2020 19:33:00 +0100
Subject: [PATCH] GQUIC: add decoding of QLVE tag

Latest GQUIC versions encapsulate their first flight in Q043 packets.
---
 epan/dissectors/packet-gquic.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/epan/dissectors/packet-gquic.c b/epan/dissectors/packet-gquic.c
index f6728d2524..1c1058659d 100644
--- a/epan/dissectors/packet-gquic.c
+++ b/epan/dissectors/packet-gquic.c
@@ -32,6 +32,7 @@ void proto_reg_handoff_gquic(void);
 
 static dissector_handle_t gquic_handle;
 static dissector_handle_t tls13_handshake_handle;
+static dissector_handle_t quic_handle;
 
 static int proto_gquic = -1;
 static int hf_gquic_header_form = -1;
@@ -167,6 +168,7 @@ static int hf_gquic_tag_sttl = -1;
 static int hf_gquic_tag_smhl = -1;
 static int hf_gquic_tag_tbkp = -1;
 static int hf_gquic_tag_mad0 = -1;
+static int hf_gquic_tag_qlve = -1;
 
 /* Public Reset Tags */
 static int hf_gquic_tag_rnon = -1;
@@ -427,6 +429,7 @@ static const value_string message_tag_vals[] = {
 #define TAG_SMHL 0x534D484C
 #define TAG_TBKP 0x54424B50
 #define TAG_MAD0 0x4d414400
+#define TAG_QLVE 0x514C5645
 
 /* Public Reset Tag */
 #define TAG_RNON 0x524E4F4E
@@ -474,6 +477,7 @@ static const value_string tag_vals[] = {
     { TAG_SMHL, "Support Max Header List (size)" },
     { TAG_TBKP, "Token Binding Key Params" },
     { TAG_MAD0, "Max Ack Delay (IETF QUIC)" },
+    { TAG_QLVE, "Legacy Version Encapsulation" },
 
     { TAG_RNON, "Public Reset Nonce Proof" },
     { TAG_RSEQ, "Rejected Packet Number" },
@@ -1655,6 +1659,18 @@ dissect_gquic_tag(tvbuff_t *tvb, packet_info *pinfo, proto_tree *gquic_tree, gui
                 proto_item_append_text(ti_tag, ": %u", tvb_get_guint32(tvb, tag_offset_start + tag_offset, ENC_LITTLE_ENDIAN));
                 tag_offset += 4;
             break;
+            case TAG_QLVE:
+            {
+                proto_tree_add_item(tag_tree, hf_gquic_tag_qlve, tvb, tag_offset_start + tag_offset, tag_len, ENC_NA);
+
+                /* Newest GQUIC versions (usually Q050) encapsulate their first flight in Q043 packets.
+		 * (Q050 is handled by QUIC dissector) */
+                tvbuff_t *next_tvb = tvb_new_subset_length(tvb, tag_offset_start + tag_offset, tag_len);
+                call_dissector_with_data(quic_handle, next_tvb, pinfo, tag_tree, NULL);
+
+                tag_offset += tag_len;
+            }
+            break;
             default:
                 proto_tree_add_item(tag_tree, hf_gquic_tag_unknown, tvb, tag_offset_start + tag_offset, tag_len, ENC_NA);
                 expert_add_info_format(pinfo, ti_tag, &ei_gquic_tag_undecoded,
@@ -3143,6 +3159,11 @@ proto_register_gquic(void)
               FT_UINT32, BASE_DEC, NULL, 0x0,
               NULL, HFILL }
         },
+        { &hf_gquic_tag_qlve,
+            { "Legacy Version Encapsulation", "gquic.tag.qlve",
+              FT_BYTES, BASE_NONE, NULL, 0x0,
+              NULL, HFILL }
+        },
 
         { &hf_gquic_tag_unknown,
             { "Unknown tag", "gquic.tag.unknown",
@@ -3209,6 +3230,7 @@ void
 proto_reg_handoff_gquic(void)
 {
     tls13_handshake_handle = find_dissector("tls13-handshake");
+    quic_handle = find_dissector("quic");
     dissector_add_uint_range_with_preference("udp.port", "", gquic_handle);
     heur_dissector_add("udp", dissect_gquic_heur, "Google QUIC", "gquic", proto_gquic, HEURISTIC_ENABLE);
 }