L2TP: Use the IANA assigned PW types for Decode As

Instead of registering subdissectors to arbitrary Wireshark
assigned numbers, register them to the actual pseudowire type
number assigned by IANA and present in the Pseudowire Type AVP.
Half of the previously registered types were never used, because
the dissector table could not be called with their Wireshark
internal number.

This makes it easier to add dissectors to support currently
unsupported but assigned types, and also makes it more intuitive
to use Decode As when the PW Type AVP is not present. Previously,
the dissector for the "default" type of CHDLC had to be changed to
a different subdissector.

11 files changed, 81 insertions, 72 deletions

diff --git a/epan/dissectors/packet-chdlc.c b/epan/dissectors/packet-chdlc.c
index 3955a041dd..c1b1f3d9b2 100644
--- a/epan/dissectors/packet-chdlc.c
+++ b/epan/dissectors/packet-chdlc.c
@@ -254,7 +254,7 @@ proto_reg_handoff_chdlc(void)
   dissector_add_uint("wtap_encap", WTAP_ENCAP_CHDLC, chdlc_handle);
   dissector_add_uint("wtap_encap", WTAP_ENCAP_CHDLC_WITH_PHDR, chdlc_handle);
   dissector_add_uint("juniper.proto", JUNIPER_PROTO_CHDLC, chdlc_handle);
-  dissector_add_uint("l2tp.pw_type", L2TPv3_PROTOCOL_CHDLC, chdlc_handle);
+  dissector_add_uint("l2tp.pw_type", L2TPv3_PW_CHDLC, chdlc_handle);
 
   chdlc_cap_handle = find_capture_dissector("chdlc");
   capture_dissector_add_uint("wtap_encap", WTAP_ENCAP_CHDLC, chdlc_cap_handle);
diff --git a/epan/dissectors/packet-ehdlc.c b/epan/dissectors/packet-ehdlc.c
index b5c226cf3b..2cfca978c5 100644
--- a/epan/dissectors/packet-ehdlc.c
+++ b/epan/dissectors/packet-ehdlc.c
@@ -462,7 +462,7 @@ proto_reg_handoff_ehdlc(void)
 	sub_handles[SUB_PGSL]  = find_dissector_add_dependency("gsm_abis_pgsl", proto_ehdlc);
 	sub_handles[SUB_DATA] = find_dissector("data");
 
-	dissector_add_uint("l2tp.pw_type", L2TPv3_PROTOCOL_ERICSSON, ehdlc_handle);
+	dissector_add_for_decode_as("l2tp.pw_type", ehdlc_handle);
 }
 
 /*
diff --git a/epan/dissectors/packet-eth.c b/epan/dissectors/packet-eth.c
index 33ea94f3bd..000e75ade4 100644
--- a/epan/dissectors/packet-eth.c
+++ b/epan/dissectors/packet-eth.c
@@ -1190,7 +1190,7 @@ proto_reg_handoff_eth(void)
   dissector_add_uint("gre.proto", GRE_MIKROTIK_EOIP, eth_withoutfcs_handle);
   dissector_add_uint("juniper.proto", JUNIPER_PROTO_ETHER, eth_withoutfcs_handle);
   dissector_add_uint("sflow_245.header_protocol", SFLOW_245_HEADER_ETHERNET, eth_withoutfcs_handle);
-  dissector_add_uint("l2tp.pw_type", L2TPv3_PROTOCOL_ETH, eth_withoutfcs_handle);
+  dissector_add_uint("l2tp.pw_type", L2TPv3_PW_ETH, eth_withoutfcs_handle);
   dissector_add_uint("vxlan.next_proto", VXLAN_ETHERNET, eth_withoutfcs_handle);
   dissector_add_uint("sll.ltype", LINUX_SLL_P_ETHERNET, eth_withoutfcs_handle);
   dissector_add_uint("nsh.next_proto", NSH_ETHERNET, eth_withoutfcs_handle);
diff --git a/epan/dissectors/packet-fr.c b/epan/dissectors/packet-fr.c
index 925ea99e29..a4abdbf17c 100644
--- a/epan/dissectors/packet-fr.c
+++ b/epan/dissectors/packet-fr.c
@@ -1117,7 +1117,7 @@ proto_reg_handoff_fr(void)
   dissector_add_uint("juniper.proto", JUNIPER_PROTO_FRELAY, fr_handle);
   dissector_add_uint("sflow_245.header_protocol", SFLOW_245_HEADER_FRAME_RELAY, fr_handle);
   dissector_add_uint("atm.aal5.type", TRAF_FR, fr_handle);
-  dissector_add_uint("l2tp.pw_type", L2TPv3_PROTOCOL_FR, fr_handle);
+  dissector_add_uint("l2tp.pw_type", L2TPv3_PW_FR, fr_handle);
   dissector_add_uint("sll.hatype", ARPHRD_FRAD, fr_handle);
 
   fr_phdr_handle = create_dissector_handle(dissect_fr_phdr, proto_fr);
diff --git a/epan/dissectors/packet-ip.c b/epan/dissectors/packet-ip.c
index 982a3ab7f6..b62224ba38 100644
--- a/epan/dissectors/packet-ip.c
+++ b/epan/dissectors/packet-ip.c
@@ -3068,7 +3068,7 @@ proto_reg_handoff_ip(void)
   dissector_add_uint("pwach.channel_type", PW_ACH_TYPE_IPV4, ip_handle);
   dissector_add_uint("mcc.proto", PW_ACH_TYPE_IPV4, ip_handle);
   dissector_add_uint("sflow_245.header_protocol", SFLOW_245_HEADER_IPv4, ip_handle);
-  dissector_add_uint("l2tp.pw_type", L2TPv3_PROTOCOL_IP, ip_handle);
+  dissector_add_uint("l2tp.pw_type", L2TPv3_PW_IP, ip_handle);
   dissector_add_for_decode_as_with_preference("udp.port", ip_handle);
   dissector_add_for_decode_as("pcli.payload", ip_handle);
   dissector_add_uint("wtap_encap", WTAP_ENCAP_RAW_IP4, ip_handle);
diff --git a/epan/dissectors/packet-l2tp.c b/epan/dissectors/packet-l2tp.c
index c32834ffbd..88d62f4189 100644
--- a/epan/dissectors/packet-l2tp.c
+++ b/epan/dissectors/packet-l2tp.c
@@ -306,7 +306,6 @@ static const enum_val_t l2tpv3_cookies[] = {
 };
 
 #define L2TPv3_COOKIE_DEFAULT       0
-#define L2TPv3_PROTOCOL_DEFAULT     L2TPv3_PROTOCOL_CHDLC
 
 #define L2TPv3_L2_SPECIFIC_NONE         0
 #define L2TPv3_L2_SPECIFIC_DEFAULT      1
@@ -881,26 +880,26 @@ static const value_string l2tp_cablel_modulation_vals[] = {
 };
 
 static const value_string pw_types_vals[] = {
-    { 0x0001,  "Frame Relay DLCI" },
-    { 0x0002,  "ATM AAL5 SDU VCC transport" },
-    { 0x0003,  "ATM Cell transparent Port Mode" },
-    { 0x0004,  "Ethernet VLAN" },
-    { 0x0005,  "Ethernet" },
-    { 0x0006,  "HDLC" },
-    { 0x0007,  "PPP" },
-    { 0x0009,  "ATM Cell transport VCC Mode" },
-    { 0x000A,  "ATM Cell transport VPC Mode" },
-    { 0x000B,  "IP Transport" },
-    { 0x000C,  "MPEG-TS Payload Type (MPTPW)" },
-    { 0x000D,  "Packet Streaming Protocol (PSPPW)" },
+    { L2TPv3_PW_FR,          "Frame Relay DLCI" },
+    { L2TPv3_PW_AAL5,        "ATM AAL5 SDU VCC transport" },
+    { L2TPv3_PW_ATM_PORT,    "ATM Cell transparent Port Mode" },
+    { L2TPv3_PW_ETH_VLAN,    "Ethernet VLAN" },
+    { L2TPv3_PW_ETH,         "Ethernet" },
+    { L2TPv3_PW_CHDLC,       "HDLC" },
+    { L2TPv3_PW_PPP,         "PPP" }, /* Currently unassigned */
+    { L2TPv3_PW_ATM_VCC,     "ATM Cell transport VCC Mode" },
+    { L2TPv3_PW_ATM_VPC,     "ATM Cell transport VPC Mode" },
+    { L2TPv3_PW_IP,          "IP Transport" }, /* Currently unassigned */
+    { L2TPv3_PW_DOCSIS_DMPT, "MPEG-TS Payload Type (MPTPW)" },
+    { L2TPv3_PW_DOCSIS_PSP,  "Packet Streaming Protocol (PSPPW)" },
     /* 0x000E-0x0010 Unassigned */
-    { 0x0011,  "Structure-agnostic E1 circuit" },       /* [RFC5611] */
-    { 0x0012,  "Structure-agnostic T1 (DS1) circuit" }, /* [RFC5611]   */
-    { 0x0013,  "Structure-agnostic E3 circuit" },       /* [RFC5611]   */
-    { 0x0014,  "Structure-agnostic T3 (DS3) circuit" }, /* [RFC5611]   */
-    { 0x0015,  "CESoPSN basic mode" },                  /* [RFC5611]   */
-    { 0x0016,  "Unassigned" },
-    { 0x0017,  "CESoPSN TDM with CAS" },                /* [RFC5611]  */
+    { L2TPv3_PW_E1,          "Structure-agnostic E1 circuit" },       /* [RFC5611]  */
+    { L2TPv3_PW_T1,          "Structure-agnostic T1 (DS1) circuit" }, /* [RFC5611]  */
+    { L2TPv3_PW_E3,          "Structure-agnostic E3 circuit" },       /* [RFC5611]  */
+    { L2TPv3_PW_T3,          "Structure-agnostic T3 (DS3) circuit" }, /* [RFC5611]  */
+    { L2TPv3_PW_CESOPSN,     "CESoPSN basic mode" },                  /* [RFC5611]  */
+    { 0x0016,                "Unassigned" },
+    { L2TPv3_PW_CESOPSN_CAS, "CESoPSN TDM with CAS" },                /* [RFC5611]  */
 
     { 0,  NULL },
 };
@@ -1005,7 +1004,7 @@ typedef struct l2tpv3_session {
     lcce_settings_t lcce1;
     lcce_settings_t lcce2;
 
-    gint    pw_type;
+    guint    pw_type;
 } l2tpv3_session_t;
 
 static const gchar* shared_secret = "";
@@ -1243,7 +1242,7 @@ static void init_session(l2tpv3_session_t *session)
 {
     session->lcce1.cookie_len = session->lcce2.cookie_len = -1;
     session->lcce1.l2_specific = session->lcce2.l2_specific = -1;
-    session->pw_type = -1;
+    session->pw_type = L2TPv3_PW_DEFAULT;
 }
 
 static l2tpv3_session_t *alloc_session(void)
@@ -1350,8 +1349,6 @@ static l2tpv3_session_t *store_pw_type(l2tpv3_session_t *_session,
                                      int msg_type)
 {
     l2tpv3_session_t *session = _session;
-    gint result = -1;
-    guint16 pw_type;
 
     switch (msg_type) {
         case MESSAGE_TYPE_ICRQ:
@@ -1364,23 +1361,7 @@ static l2tpv3_session_t *store_pw_type(l2tpv3_session_t *_session,
     if (session == NULL)
         session = alloc_session();
 
-    pw_type = tvb_get_ntohs(tvb, offset);
-    switch (pw_type) {
-        case 0x0007:
-            result = L2TPv3_PROTOCOL_PPP; break;
-        case 0x0005:
-            result = L2TPv3_PROTOCOL_ETH; break;
-        case 0x0006:
-            result = L2TPv3_PROTOCOL_CHDLC; break;
-        case 0x0002:
-            result = L2TPv3_PROTOCOL_AAL5; break;
-        case 0x0001:
-            result = L2TPv3_PROTOCOL_FR; break;
-        default:
-            break;
-    }
-
-    session->pw_type = result;
+    session->pw_type = tvb_get_ntohs(tvb, offset);
 
     return session;
 }
@@ -1473,7 +1454,7 @@ static void update_session(l2tpv3_tunnel_t *tunnel, l2tpv3_session_t *session)
     if (session->lcce2.l2_specific != -1)
         existing->lcce2.l2_specific = session->lcce2.l2_specific;
 
-    if (session->pw_type != -1)
+    if (session->pw_type != L2TPv3_PW_DEFAULT)
         existing->pw_type = session->pw_type;
 
     if (tunnel->sessions == NULL) {
@@ -1486,7 +1467,7 @@ static void update_session(l2tpv3_tunnel_t *tunnel, l2tpv3_session_t *session)
 
 static void l2tp_prompt(packet_info *pinfo _U_, gchar* result)
 {
-    snprintf(result, MAX_DECODE_AS_PROMPT_LEN, "Decode L2TPv3 packet type 0x%04x as",
+    snprintf(result, MAX_DECODE_AS_PROMPT_LEN, "Decode L2TPv3 pseudowire type 0x%04x as",
         GPOINTER_TO_UINT(p_get_proto_data(pinfo->pool, pinfo, proto_l2tp, 0)));
 }
 
@@ -2536,7 +2517,7 @@ process_l2tpv3_data(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
     tvbuff_t   *next_tvb;
     gint        cookie_len  = l2tpv3_cookie;
     gint        l2_spec     = l2tpv3_l2_specific;
-    gint        pw_type     = -1;
+    guint       pw_type     = L2TPv3_PW_DEFAULT;
 
     lcce_settings_t  *lcce      = NULL;
     l2tpv3_session_t *session   = NULL;
@@ -2562,16 +2543,13 @@ process_l2tpv3_data(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
             l2_spec = lcce->l2_specific;
         if (cookie_len == -1)
             cookie_len = lcce->cookie_len;
-        if (pw_type == -1)
+        if (pw_type == L2TPv3_PW_DEFAULT)
             pw_type = session->pw_type;
     }
 
     if (l2_spec == -1)
         l2_spec = L2TPv3_L2_SPECIFIC_NONE;
 
-    if (pw_type == -1)
-        pw_type = L2TPv3_PROTOCOL_DEFAULT;
-
     if (cookie_len == -1)
         cookie_len = L2TPv3_COOKIE_DEFAULT;
 
@@ -2663,7 +2641,7 @@ process_l2tpv3_data(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
         break;
     }
 
-    p_add_proto_data(pinfo->pool, pinfo, proto_l2tp, 0, GUINT_TO_POINTER((guint)pw_type));
+    p_add_proto_data(pinfo->pool, pinfo, proto_l2tp, 0, GUINT_TO_POINTER(pw_type));
 
     if (!dissector_try_uint_new(pw_type_table, pw_type, next_tvb, pinfo, tree, FALSE, GUINT_TO_POINTER(oam_cell)))
     {
@@ -3754,7 +3732,7 @@ proto_register_l2tp(void)
     expert_register_field_array(expert_l2tp, ei, array_length(ei));
 
     l2tp_vendor_avp_dissector_table = register_dissector_table("l2tp.vendor_avp", "L2TP vendor AVP dissector table", proto_l2tp, FT_UINT32, BASE_DEC);
-    pw_type_table = register_dissector_table("l2tp.pw_type", "L2TPv3 payload type", proto_l2tp, FT_UINT32, BASE_DEC);
+    pw_type_table = register_dissector_table("l2tp.pw_type", "L2TPv3 pseudowire type", proto_l2tp, FT_UINT32, BASE_DEC);
 
     l2tp_module = prefs_register_protocol(proto_l2tp, NULL);
 
@@ -3774,7 +3752,10 @@ proto_register_l2tp(void)
                                    l2tpv3_l2_specifics,
                                    FALSE);
 
-    prefs_register_obsolete_preference(l2tp_module, "protocol");
+    prefs_register_static_text_preference(l2tp_module, "protocol",
+        "Dissection of pseudowire types is configured through \"Decode As\". "
+        "Type 0 is used for sessions with unknown pseudowire type.",
+        "Pseudowire Type \"Decode As\" instuctions");
 
     prefs_register_string_preference(l2tp_module,"shared_secret","Shared Secret",
                                    "Shared secret used for control message digest authentication",
@@ -3812,7 +3793,12 @@ proto_reg_handoff_l2tp(void)
     llc_handle            = find_dissector_add_dependency("llc", proto_l2tp);
 
     atm_oam_llc_handle = create_dissector_handle( dissect_atm_oam_llc, proto_l2tp );
-    dissector_add_uint("l2tp.pw_type", L2TPv3_PROTOCOL_AAL5, atm_oam_llc_handle);
+    dissector_add_uint("l2tp.pw_type", L2TPv3_PW_AAL5, atm_oam_llc_handle);
+
+    /*
+     * XXX: Should we register something (Ethernet?) to L2TPv3_PW_DEFAULT?
+     * The user could always change it with Decode As.
+     */
 }
 
 /*
diff --git a/epan/dissectors/packet-l2tp.h b/epan/dissectors/packet-l2tp.h
index 16e06ddaa0..20449d76c1 100644
--- a/epan/dissectors/packet-l2tp.h
+++ b/epan/dissectors/packet-l2tp.h
@@ -15,16 +15,39 @@ typedef struct _l2tp_cntrl_data {
 	int         msg_type;
 } l2tp_cntrl_data_t;
 
-#define L2TPv3_PROTOCOL_ETH         0
-#define L2TPv3_PROTOCOL_CHDLC       1
-#define L2TPv3_PROTOCOL_FR          2
-#define L2TPv3_PROTOCOL_PPP         3
-#define L2TPv3_PROTOCOL_IP          4
-#define L2TPv3_PROTOCOL_MPLS        5
-#define L2TPv3_PROTOCOL_AAL5        6
-#define L2TPv3_PROTOCOL_LAPD        7
-#define L2TPv3_PROTOCOL_DOCSIS_DMPT 8
-#define L2TPv3_PROTOCOL_ERICSSON    9
-#define L2TPv3_PROTOCOL_MAX         (L2TPv3_PROTOCOL_ERICSSON + 1)
+/* L2TPv3 Pseudowire Types
+ * https://www.iana.org/assignments/l2tp-parameters/l2tp-parameters.xhtml
+ */
+/* 0 is unassigned, use for Decode As of sessions where we do not have a
+ * PW Type AVP. (Perhaps if no control packets are captured.)  */
+#define L2TPv3_PW_DEFAULT     0x0000
+#define L2TPv3_PW_FR          0x0001
+#define L2TPv3_PW_AAL5        0x0002
+#define L2TPv3_PW_ATM_PORT    0x0003
+#define L2TPv3_PW_ETH_VLAN    0x0004
+#define L2TPv3_PW_ETH         0x0005
+#define L2TPv3_PW_CHDLC       0x0006
+#define L2TPv3_PW_PPP         0x0007 /* Expired draft, unassigned */
+#define L2TPv3_PW_ATM_VCC     0x0009
+#define L2TPv3_PW_ATM_VPC     0x000A
+#define L2TPv3_PW_IP          0x000B /* Expired draft, unassigned */
+#define L2TPv3_PW_DOCSIS_DMPT 0x000C /* MPEG2-TS */
+#define L2TPv3_PW_DOCSIS_PSP  0x000D
+#define L2TPv3_PW_E1          0x0011
+#define L2TPv3_PW_T1          0x0012
+#define L2TPv3_PW_E3          0x0013
+#define L2TPv3_PW_T3          0x0014
+#define L2TPv3_PW_CESOPSN     0x0015
+#define L2TPv3_PW_CESOPSN_CAS 0x0017
+
+#if 0
+/* Other dissectors that do not have Pseudowire Types assigned.
+ * Were any of the unassigned numbers used for these in the past,
+ * as with PPP and IP?
+ */
+#define L2TPv3_PW_MPLS
+#define L2TPv3_PW_LAPD
+#define L2TPv3_PW_ERICSSON
+#endif
 
 #endif /* __PACKET_L2TP_H__ */
diff --git a/epan/dissectors/packet-lapd.c b/epan/dissectors/packet-lapd.c
index c1f37ad9fb..2f8f4dd240 100644
--- a/epan/dissectors/packet-lapd.c
+++ b/epan/dissectors/packet-lapd.c
@@ -797,7 +797,7 @@ proto_reg_handoff_lapd(void)
 	lapd_frame_handle = create_dissector_handle(dissect_lapd_frame, proto_lapd);
 	dissector_add_uint("wtap_encap", WTAP_ENCAP_LAPD, lapd_frame_handle);
 
-	dissector_add_uint("l2tp.pw_type", L2TPv3_PROTOCOL_LAPD, lapd_handle);
+	dissector_add_for_decode_as("l2tp.pw_type", lapd_handle);
 	dissector_add_for_decode_as_with_preference("sctp.ppi", lapd_handle);
 	dissector_add_for_decode_as("sctp.port", lapd_handle);
 	dissector_add_uint_range_with_preference("udp.port", "", lapd_handle);
diff --git a/epan/dissectors/packet-mp2t.c b/epan/dissectors/packet-mp2t.c
index f165753331..8ee267309d 100644
--- a/epan/dissectors/packet-mp2t.c
+++ b/epan/dissectors/packet-mp2t.c
@@ -1847,7 +1847,7 @@ proto_reg_handoff_mp2t(void)
     dissector_add_for_decode_as_with_preference("udp.port", mp2t_handle);
     heur_dissector_add("usb.bulk", heur_dissect_mp2t, "MP2T USB bulk endpoint", "mp2t_usb_bulk", proto_mp2t, HEURISTIC_ENABLE);
     dissector_add_uint("wtap_encap", WTAP_ENCAP_MPEG_2_TS, mp2t_handle);
-    dissector_add_uint("l2tp.pw_type", L2TPv3_PROTOCOL_DOCSIS_DMPT, mp2t_handle);
+    dissector_add_uint("l2tp.pw_type", L2TPv3_PW_DOCSIS_DMPT, mp2t_handle);
     dissector_add_string("media_type", "video/mp2t", mp2t_handle);
 
     docsis_handle = find_dissector("docsis");
diff --git a/epan/dissectors/packet-mpls.c b/epan/dissectors/packet-mpls.c
index ad0cf2f1f0..7d6e98d676 100644
--- a/epan/dissectors/packet-mpls.c
+++ b/epan/dissectors/packet-mpls.c
@@ -719,7 +719,7 @@ proto_reg_handoff_mpls(void)
     dissector_add_uint("juniper.proto", JUNIPER_PROTO_CLNP_MPLS, mpls_handle);
     dissector_add_for_decode_as("pwach.channel_type", mpls_handle);
     dissector_add_uint("sflow_245.header_protocol", SFLOW_245_HEADER_MPLS, mpls_handle);
-    dissector_add_uint("l2tp.pw_type", L2TPv3_PROTOCOL_MPLS, mpls_handle);
+    dissector_add_for_decode_as("l2tp.pw_type", mpls_handle);
     dissector_add_uint_with_preference("udp.port", UDP_PORT_MPLS_OVER_UDP, mpls_handle);
     dissector_add_uint("vxlan.next_proto", VXLAN_MPLS, mpls_handle);
     dissector_add_uint("nsh.next_proto", NSH_MPLS, mpls_handle);
diff --git a/epan/dissectors/packet-ppp.c b/epan/dissectors/packet-ppp.c
index 6e10bf007e..7f2294fde3 100644
--- a/epan/dissectors/packet-ppp.c
+++ b/epan/dissectors/packet-ppp.c
@@ -6530,7 +6530,7 @@ proto_reg_handoff_ppp(void)
     dissector_add_uint("gre.proto", ETHERTYPE_PPP, ppp_hdlc_handle);
     dissector_add_uint("juniper.proto", JUNIPER_PROTO_PPP, ppp_handle);
     dissector_add_uint("sflow_245.header_protocol", SFLOW_245_HEADER_PPP, ppp_hdlc_handle);
-    dissector_add_uint("l2tp.pw_type", L2TPv3_PROTOCOL_PPP, ppp_hdlc_handle);
+    dissector_add_uint("l2tp.pw_type", L2TPv3_PW_PPP, ppp_hdlc_handle);
 }
 
 void