/* packet-epon.c * Routines for Ethernet Passive Optical Network dissection * Copyright 2014, Philip Rosenberg-Watt * * Wireshark - Network traffic analyzer * By Gerald Combs * Copyright 1998 Gerald Combs * * SPDX-License-Identifier: GPL-2.0-or-later */ /* 2014-04 Philip Rosenberg-Watt * + EPON preamble with CableLabs DPoE securty byte. * See IEEE 802.3-2012 Section 5, Clause 65 and * CableLabs DPoE SEC 1.0 specification. */ #include "config.h" #include #include #include #include void proto_register_epon(void); void proto_reg_handoff_epon(void); static dissector_handle_t epon_handle; static int proto_epon = -1; static int hf_epon_dpoe_security = -1; static int hf_epon_dpoe_encrypted = -1; static int hf_epon_dpoe_reserved = -1; static int hf_epon_dpoe_encrypted_data = -1; static int hf_epon_dpoe_keyid = -1; static int hf_epon_mode = -1; static int hf_epon_llid = -1; static int hf_epon_checksum = -1; static int hf_epon_checksum_status = -1; static expert_field ei_epon_sld_bad = EI_INIT; static expert_field ei_epon_dpoe_reserved_bad = EI_INIT; static expert_field ei_epon_dpoe_bad = EI_INIT; static expert_field ei_epon_dpoe_encrypted_data = EI_INIT; static expert_field ei_epon_checksum_bad = EI_INIT; static dissector_handle_t eth_maybefcs_handle; static gint ett_epon = -1; static gint ett_epon_sec = -1; static gint ett_epon_checksum = -1; static const true_false_string epon_mode_tfs = { "Broadcast/Multicast", "Unicast" }; static int dissect_epon(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_) { proto_tree *epon_tree; proto_item *ti; proto_item *item; proto_tree *sec_tree; tvbuff_t *next_tvb; guint checksum; guint sent_checksum; guint offset = 0; guint dpoe_sec_byte; gboolean dpoe_encrypted = FALSE; /* Start_of_Packet delimiter (/S/) can happen in byte 1, 2 or 3, * making the captured preamble 8, 7 or 6 bytes in length. If the * preamble starts with 0x55, then /S/ happened in byte 1, making the * captured preamble 7 bytes in length. */ if (tvb_get_ntohl(tvb, 0) == 0x5555D555) { offset += 2; } else if (tvb_get_ntoh24(tvb, 0) == 0x55D555) { offset += 1; } else if (tvb_get_ntohs(tvb, 0) == 0xD555) { offset += 0; } else { item = proto_tree_add_item(tree, proto_epon, tvb, offset, 0, ENC_NA); expert_add_info(pinfo, item, &ei_epon_sld_bad); return 0; } /* Set the columns */ col_set_str(pinfo->cinfo, COL_PROTOCOL, "EPON"); col_set_str(pinfo->cinfo, COL_INFO, "EPON Preamble"); /* Create display subtree for the protocol */ ti = proto_tree_add_item(tree, proto_epon, tvb, 0+offset, 6, ENC_NA); epon_tree = proto_item_add_subtree(ti, ett_epon); /* Decode byte 5 of the preamble according to CableLabs DPoE specification. * If security is disabled, the DPoE byte will remain 0x55 and no decoding * is necessary. */ dpoe_sec_byte = tvb_get_guint8(tvb, 2+offset); if (dpoe_sec_byte != 0x55) { guint dpoe_keyid; guint dpoe_reserved; item = proto_tree_add_item(epon_tree, hf_epon_dpoe_security, tvb, 2+offset, 1, ENC_BIG_ENDIAN); sec_tree = proto_item_add_subtree(item, ett_epon_sec); /* The DPoE security byte is split into three fields: * bits 7-2 are reserved in 1G mode * bit 1 is the encryption mode * bit 0 is the key ID */ dpoe_reserved = dpoe_sec_byte & 0xFC; dpoe_encrypted = dpoe_sec_byte & 0x02; dpoe_keyid = dpoe_sec_byte & 0x01; /* Add encryption status text to sec_tree subtree */ proto_item_append_text(item, " (Encrypted: "); if (dpoe_encrypted) { proto_item_append_text(item, "True, Key ID: %x", dpoe_keyid); } else { proto_item_append_text(item, "False"); } proto_item_append_text(item, ")"); /* We don't need to see the reserved bits of the DPoE security byte unless * there's something wrong with them. */ if (dpoe_reserved != 0x54) { proto_tree_add_item(sec_tree, hf_epon_dpoe_reserved, tvb, 2+offset, 1, ENC_BIG_ENDIAN); expert_add_info(pinfo, sec_tree, &ei_epon_dpoe_reserved_bad); } /* Add encryption and key ID bits * Error if encryption is disabled but key bit is not 1 */ proto_tree_add_item(sec_tree, hf_epon_dpoe_encrypted, tvb, 2+offset, 1, ENC_BIG_ENDIAN); proto_tree_add_item(sec_tree, hf_epon_dpoe_keyid, tvb, 2+offset, 1, ENC_BIG_ENDIAN); if (!dpoe_encrypted && (dpoe_keyid == 0)) { expert_add_info(pinfo, sec_tree, &ei_epon_dpoe_bad); } } /* Mode bit */ proto_tree_add_item(epon_tree, hf_epon_mode, tvb, 3+offset, 2, ENC_BIG_ENDIAN); /* LLID */ proto_tree_add_item(epon_tree, hf_epon_llid, tvb, 3+offset, 2, ENC_BIG_ENDIAN); /* Verify the CRC-8 checksum */ sent_checksum = tvb_get_guint8(tvb, 5+offset); checksum = get_crc8_ieee8023_epon(tvb, 5, 0+offset); proto_tree_add_checksum(epon_tree, tvb, 5+offset, hf_epon_checksum, hf_epon_checksum_status, &ei_epon_checksum_bad, pinfo, checksum, ENC_NA, PROTO_CHECKSUM_VERIFY); if (sent_checksum != checksum) { col_append_str(pinfo->cinfo, COL_INFO, " [EPON PREAMBLE CHECKSUM INCORRECT]"); } /* Do not bother parsing encrypted data, otherwise send the rest on to the * eth dissector. */ if (dpoe_encrypted) { item = proto_tree_add_item(tree, hf_epon_dpoe_encrypted_data, tvb, 6+offset, -1, ENC_NA); expert_add_info(pinfo, item, &ei_epon_dpoe_encrypted_data); col_append_str(pinfo->cinfo, COL_INFO, " [ENCRYPTED]"); } else { next_tvb = tvb_new_subset_remaining(tvb, 6+offset); /* * XXX - is it guaranteed whether the capture will, or won't, have * an FCS? */ call_dissector(eth_maybefcs_handle, next_tvb, pinfo, tree); } return tvb_captured_length(tvb); } void proto_register_epon(void) { expert_module_t *expert_epon; static hf_register_info hf[] = { { &hf_epon_dpoe_security, { "DPoE security", "epon.dpoe.sec", FT_UINT8, BASE_HEX, NULL, 0x0, "DPoE security octet", HFILL } }, { &hf_epon_dpoe_reserved, { "Reserved", "epon.dpoe.reserved", FT_UINT8, BASE_DEC, NULL, 0xFC, "Reserved in 1G mode", HFILL } }, { &hf_epon_dpoe_encrypted, { "Encryption enabled", "epon.dpoe.encrypted", FT_BOOLEAN, 8, NULL, 0x02, "Specifies if this is an encrypted frame", HFILL } }, { &hf_epon_dpoe_keyid, { "Key ID", "epon.dpoe.keyid", FT_UINT8, BASE_HEX, NULL, 0x01, "Identification number of the key used to encrypt this frame", HFILL } }, { &hf_epon_dpoe_encrypted_data, { "Encrypted data", "epon.dpoe.encrypted.data", FT_BYTES, BASE_NONE, NULL, 0x0, "DPoE encrypted data", HFILL } }, { &hf_epon_mode, { "Mode", "epon.mode", FT_BOOLEAN, 16, TFS(&epon_mode_tfs), 0x8000, "Broadcast/multicast if true, unicast if false", HFILL } }, { &hf_epon_llid, { "LLID", "epon.llid", FT_UINT16, BASE_DEC_HEX, NULL, 0x7FFF, "Logical Link ID", HFILL } }, { &hf_epon_checksum, { "Frame check sequence", "epon.checksum", FT_UINT8, BASE_HEX, NULL, 0x0, "EPON preamble checksum", HFILL } }, { &hf_epon_checksum_status, { "Frame check sequence Status", "epon.checksum.status", FT_UINT8, BASE_NONE, VALS(proto_checksum_vals), 0x0, NULL, HFILL } }, }; static gint *ett[] = { &ett_epon, &ett_epon_sec, &ett_epon_checksum }; /* Setup protocol expert items */ static ei_register_info ei[] = { { &ei_epon_checksum_bad, { "epon.checksum_bad.expert", PI_CHECKSUM, PI_ERROR, "Bad checksum", EXPFILL } }, { &ei_epon_sld_bad, { "epon.sld_bad.expert", PI_MALFORMED, PI_ERROR, "Unable to locate SLD or invalid byte sequence: preamble must start with 0xD555", EXPFILL } }, { &ei_epon_dpoe_reserved_bad, { "epon.dpoe.encrypted.expert", PI_MALFORMED, PI_ERROR, "Bits 7-2 of DPoE security byte must be 010101 in 1G mode.", EXPFILL } }, { &ei_epon_dpoe_bad, { "epon.dpoe.expert", PI_MALFORMED, PI_ERROR, "DPoE security byte must be 0x55 if encryption is disabled.", EXPFILL } }, { &ei_epon_dpoe_encrypted_data, { "epon.dpoe.encrypted.expert", PI_UNDECODED, PI_NOTE, "Remaining data is encrypted and will not decode.", EXPFILL } } }; proto_epon = proto_register_protocol("IEEE 802.3 EPON Preamble", "EPON", "epon"); proto_register_field_array(proto_epon, hf, array_length(hf)); proto_register_subtree_array(ett, array_length(ett)); expert_epon = expert_register_protocol(proto_epon); expert_register_field_array(expert_epon, ei, array_length(ei)); epon_handle = register_dissector("epon", dissect_epon, proto_epon); } void proto_reg_handoff_epon(void) { dissector_add_uint("wtap_encap", WTAP_ENCAP_EPON, epon_handle); eth_maybefcs_handle = find_dissector_add_dependency("eth_maybefcs", proto_epon); } /* * Editor modelines - https://www.wireshark.org/tools/modelines.html * * Local Variables: * c-basic-offset: 2 * tab-width: 8 * indent-tabs-mode: nil * End: * * ex: set shiftwidth=2 tabstop=8 expandtab: * :indentSize=2:tabSize=8:noTabs=true: */