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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.
This commit is contained in:
John Thacker 2022-08-10 20:47:51 -04:00
parent 34ab3f308a
commit ee6519bca6
11 changed files with 81 additions and 72 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
epan/dissectors/packet-chdlc.c
View File

@ -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);

2
epan/dissectors/packet-ehdlc.c
View File

@ -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);
}
/*

2
epan/dissectors/packet-eth.c
View File

@ -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);

2
epan/dissectors/packet-fr.c
View File

@ -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);

2
epan/dissectors/packet-ip.c
View File

@ -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);

90
epan/dissectors/packet-l2tp.c
View File

@ -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.
*/
}
/*

45
epan/dissectors/packet-l2tp.h
View File

@ -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__ */

2
epan/dissectors/packet-lapd.c
View File

@ -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);

2
epan/dissectors/packet-mp2t.c
View File

@ -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");

2
epan/dissectors/packet-mpls.c
View File

@ -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);

2
epan/dissectors/packet-ppp.c
View File

@ -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