/* packet-vj-comp.c * Routines for decompression of PPP Van Jacobson compression * RFC 1144 * * Wireshark - Network traffic analyzer * By Gerald Combs * * SPDX-License-Identifier: GPL-2.0-or-later */ /* The routines in this file were created by reading the description of * RFC 1144 available here: ftp://ftp.rfc-editor.org/in-notes/rfc1144.pdf * ONLY the description of the protocol in section 3.2 was used. * Notably, the sample implementation in Appendix A was NOT read by this file's * author, due to the questionable legality of using it in Wireshark. * For details on this issue, see: * https://gitlab.com/wireshark/wireshark/-/issues/12138 */ /* Currently hard-coded to assume TCP over IPv4. * Nothing in the standard explicitly prevents an IPv6 implementation... */ #include "config.h" #include #include #include #include #include #include #include #include #include #include #include "packet-ip.h" #include "packet-ppp.h" /* Shorthand macros for reading/writing 16/32 bit values from * possibly-unaligned indexes into a uint8_t[] */ #define GET_16(p,i) (uint16_t)(((p)[(i)] << 8) | ((p)[(i)+1])) #define GET_32(p,i) (uint32_t)(((p)[(i)] << 24) | ((p)[(i)+1] << 16) | ((p)[(i)+2] << 8) | ((p)[(i)+3])) #define PUT_16(p,i,v) G_STMT_START { \ (p)[(i)] = ((v) & 0xFF00) >> 8; \ (p)[(i)+1] = ((v) & 0x00FF); \ } G_STMT_END #define PUT_32(p,i,v) G_STMT_START { \ (p)[(i)] = ((v) & 0xFF000000) >> 24; \ (p)[(i)+1] = ((v) & 0x00FF0000) >> 16; \ (p)[(i)+2] = ((v) & 0x0000FF00) >> 8; \ (p)[(i)+3] = ((v) & 0x000000FF); \ } G_STMT_END /* Store the last connection number we've seen. * Only used on the first pass, in case the connection number itself * gets compressed out. */ #define CNUM_INVALID UINT16_MAX static uint16_t last_cnum = CNUM_INVALID; /* Location in an IPv4 packet of the IP Next Protocol field * (which VJC replaces with the connection ID in uncompressed packets) */ #define VJC_CONNID_OFFSET 9 /* Minimum TCP header length. We get compression data from the TCP header, * and also store it for future use. */ #define VJC_TCP_HDR_LEN 20 /* Structure for tracking the changeable parts of a packet header */ typedef struct vjc_hdr_s { uint16_t tcp_chksum; uint16_t urg; uint16_t win; uint32_t seq; uint32_t ack; uint32_t ip_id; bool psh; } vjc_hdr_t; /* The structure used in a wireshark "conversation" */ typedef struct vjc_conv_s { uint32_t last_frame; // On first pass, where to get the previous info uint32_t last_frame_len; // On first pass, length of prev. frame (for SAWU/SWU) uint8_t *frame_headers; // Full copy of the IP header uint8_t header_len; // Length of the stored IP header wmem_map_t *vals; // Hash of frame_number => vjc_hdr_t* } vjc_conv_t; static dissector_handle_t vjcu_handle; static dissector_handle_t vjcc_handle; static dissector_handle_t ip_handle; void proto_register_vjc(void); void proto_reg_handoff_vjc(void); static int proto_vjc; static int ett_vjc; static int ett_vjc_change_mask; static expert_field ei_vjc_sawu; static expert_field ei_vjc_swu; static expert_field ei_vjc_no_cnum; static expert_field ei_vjc_no_conversation; static expert_field ei_vjc_no_direction; static expert_field ei_vjc_no_conv_data; static expert_field ei_vjc_undecoded; static expert_field ei_vjc_bad_data; static expert_field ei_vjc_error; #define VJC_FLAG_R 0x80 #define VJC_FLAG_C 0x40 #define VJC_FLAG_I 0x20 #define VJC_FLAG_P 0x10 #define VJC_FLAG_S 0x08 #define VJC_FLAG_A 0x04 #define VJC_FLAG_W 0x02 #define VJC_FLAG_U 0x01 #define VJC_FLAGS_SAWU 0x0F #define VJC_FLAGS_SWU 0x0B static int hf_vjc_comp; static int hf_vjc_cnum; static int hf_vjc_change_mask; static int hf_vjc_change_mask_r; static int hf_vjc_change_mask_c; static int hf_vjc_change_mask_i; static int hf_vjc_change_mask_p; static int hf_vjc_change_mask_s; static int hf_vjc_change_mask_a; static int hf_vjc_change_mask_w; static int hf_vjc_change_mask_u; static int hf_vjc_chksum; static int hf_vjc_urg; static int hf_vjc_d_win; static int hf_vjc_d_ack; static int hf_vjc_d_seq; static int hf_vjc_d_ipid; static int hf_vjc_tcpdata; static int * const vjc_change_mask_fields[] = { &hf_vjc_change_mask_r, &hf_vjc_change_mask_c, &hf_vjc_change_mask_i, &hf_vjc_change_mask_p, &hf_vjc_change_mask_s, &hf_vjc_change_mask_a, &hf_vjc_change_mask_w, &hf_vjc_change_mask_u, NULL }; /* Initialization routine. Called at start of dissection. * Registered in proto_register_vjc() below. */ static void vjc_init_protocol(void) { last_cnum = CNUM_INVALID; } /* Cleanup routine. Called at close of file. * Registered in proto_register_vjc() below. */ static void vjc_cleanup_protocol(void) { last_cnum = CNUM_INVALID; } /* Find (or optionally create) a VJC conversation. */ static conversation_t * vjc_find_conversation(packet_info *pinfo, uint32_t vjc_cnum, bool create) { /* PPP gives us almost nothing to hook a conversation on; just whether * the packet is considered to be P2P_DIR_RECV or P2P_DIR_SENT. * Ideally we should also be distinguishing conversations based on the * capture interface, VLAN ID, MPLS tags, etc., etc. but that's beyond * the scope of this dissector, and a perennial problem in Wireshark anyway. * See */ conversation_t *conv = (conversation_t *)NULL; switch (pinfo->p2p_dir) { case P2P_DIR_RECV: vjc_cnum |= 0x0100; break; case P2P_DIR_SENT: vjc_cnum |= 0x0200; break; default: return conv; } conv = find_conversation_by_id(pinfo->num, CONVERSATION_NONE, vjc_cnum); if (!conv && create) { conv = conversation_new_by_id(pinfo->num, CONVERSATION_NONE, vjc_cnum); } return conv; } /* RFC 1144 section 3.2.2 says that "deltas" are sent for many values in the * header. If the initial byte is 0, that means the following 2 bytes are the * 16-bit value of the delta. Otherwise, the initial byte is the 8-bit value. */ static uint32_t vjc_delta_uint(proto_tree *tree, int hf, tvbuff_t *tvb, unsigned *offset) { uint32_t ret_val; if (0 != tvb_get_uint8(tvb, *offset)) { proto_tree_add_item_ret_uint(tree, hf, tvb, *offset, 1, ENC_BIG_ENDIAN, &ret_val); (*offset)++; } else { (*offset)++; proto_tree_add_item_ret_uint(tree, hf, tvb, *offset, 2, ENC_BIG_ENDIAN, &ret_val); *offset += 2; } return ret_val; } /* Same thing but signed, since the TCP window delta can be negative */ static int32_t vjc_delta_int(proto_tree *tree, int hf, tvbuff_t *tvb, unsigned *offset) { int32_t ret_val; if (0 != tvb_get_int8(tvb, *offset)) { proto_tree_add_item_ret_int(tree, hf, tvb, *offset, 1, ENC_BIG_ENDIAN, &ret_val); (*offset)++; } else { (*offset)++; proto_tree_add_item_ret_int(tree, hf, tvb, *offset, 2, ENC_BIG_ENDIAN, &ret_val); *offset += 2; } return ret_val; } /* Main dissection routine for uncompressed VJC packets. * Registered in proto_reg_handoff_vjc() below. */ static int dissect_vjc_uncomp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data) { /* A Van Jacobson uncompressed packet contains a standard TCP/IP header, with * the IP next protocol ID replaced with the connection number. * It's meant to signify a new TCP connection, or refresh an existing one, * which will have subsequent compressed packets. */ proto_tree *subtree = NULL; proto_item *ti = NULL; uint8_t ip_ver = 0; uint8_t ip_len = 0; unsigned tcp_len = 0; uint32_t vjc_cnum = 0; tvbuff_t *tcpip_tvb = NULL; tvbuff_t *sub_tvb = NULL; conversation_t *conv = NULL; vjc_hdr_t *this_hdr = NULL; vjc_conv_t *pkt_data = NULL; uint8_t *pdata = NULL; static uint8_t real_proto = IP_PROTO_TCP; ti = proto_tree_add_item(tree, proto_vjc, tvb, 0, -1, ENC_NA); subtree = proto_item_add_subtree(ti, ett_vjc); proto_item_set_text(subtree, "PPP Van Jacobson uncompressed TCP/IP"); /* Start with some sanity checks */ if (VJC_CONNID_OFFSET+1 > tvb_captured_length(tvb)) { proto_tree_add_expert_format(subtree, pinfo, &ei_vjc_bad_data, tvb, 0, -1, "Packet truncated before Connection ID field"); return tvb_captured_length(tvb); } ip_ver = (tvb_get_uint8(tvb, 0) & 0xF0) >> 4; ip_len = (tvb_get_uint8(tvb, 0) & 0x0F) << 2; tcp_len = ip_len + VJC_TCP_HDR_LEN; if (4 != ip_ver) { proto_tree_add_expert_format(subtree, pinfo, &ei_vjc_bad_data, tvb, 0, 1, "IPv%d unsupported for VJC compression", ip_ver); return tvb_captured_length(tvb); } /* So far so good, continue the dissection */ ti = proto_tree_add_boolean(subtree, hf_vjc_comp, tvb, 0, 0, false); proto_item_set_generated(ti); proto_tree_add_item_ret_uint(subtree, hf_vjc_cnum, tvb, VJC_CONNID_OFFSET, 1, ENC_BIG_ENDIAN, &vjc_cnum); /* Build a composite TVB containing the original TCP/IP data. * This is easy for uncompressed VJC packets because only one byte * is different from the on-the-wire data. */ sub_tvb = tvb_new_child_real_data(tvb, &real_proto, 1, 1); tvb_set_free_cb(sub_tvb, NULL); tcpip_tvb = tvb_new_composite(); tvb_composite_append(tcpip_tvb, tvb_new_subset_length(tvb, 0, VJC_CONNID_OFFSET)); tvb_composite_append(tcpip_tvb, sub_tvb); if (0 < tvb_captured_length_remaining(tvb, VJC_CONNID_OFFSET+1)) { tvb_composite_append(tcpip_tvb, tvb_new_subset_length(tvb, VJC_CONNID_OFFSET+1, -1)); } tvb_composite_finalize(tcpip_tvb); add_new_data_source(pinfo, tcpip_tvb, "Original TCP/IP data"); if (!(pinfo->p2p_dir == P2P_DIR_RECV || pinfo->p2p_dir == P2P_DIR_SENT)) { /* We can't make a proper conversation if we don't know the endpoints */ proto_tree_add_expert(subtree, pinfo, &ei_vjc_no_direction, tvb, 0, 0); } else if (tcp_len > tvb_captured_length(tvb)) { /* Not enough data. We can still pass this packet onward (though probably * to no benefit), but can't base future decompression off of it. */ proto_tree_add_expert_format(subtree, pinfo, &ei_vjc_bad_data, tvb, 0, -1, "Packet truncated before end of TCP/IP headers"); } else if (!pinfo->fd->visited) { /* If this is our first time visiting this packet, set things up for * decompressing future packets. */ last_cnum = vjc_cnum; conv = vjc_find_conversation(pinfo, vjc_cnum, true); pkt_data = (vjc_conv_t *)conversation_get_proto_data(conv, proto_vjc); if (NULL == pkt_data) { pkt_data = wmem_new0(wmem_file_scope(), vjc_conv_t); pkt_data->vals = wmem_map_new(wmem_file_scope(), g_direct_hash, g_direct_equal); conversation_add_proto_data(conv, proto_vjc, (void *)pkt_data); } pdata = // shorthand pkt_data->frame_headers = (uint8_t *)tvb_memdup(wmem_file_scope(), tcpip_tvb, 0, tcp_len); pkt_data->last_frame = pinfo->num; pkt_data->header_len = tcp_len; // This value is used for re-calculating seq/ack numbers pkt_data->last_frame_len = tvb_reported_length(tvb) - ip_len; this_hdr = wmem_new0(wmem_file_scope(), vjc_hdr_t); this_hdr->ip_id = GET_16(pdata, 4); this_hdr->seq = GET_32(pdata, ip_len + 4); this_hdr->ack = GET_32(pdata, ip_len + 8); this_hdr->psh = (pdata[ip_len + 13] & 0x08) == 0x08; this_hdr->win = GET_16(pdata, ip_len + 14); this_hdr->tcp_chksum = GET_16(pdata, ip_len + 16); this_hdr->urg = GET_16(pdata, ip_len + 18); wmem_map_insert(pkt_data->vals, GUINT_TO_POINTER(pinfo->num), this_hdr); } else { /* We've already visited this packet, we should have all the info we need. */ } return call_dissector_with_data(ip_handle, tcpip_tvb, pinfo, tree, data); } /* Main dissection routine for compressed VJC packets. * Registered in proto_reg_handoff_vjc() below. */ static int dissect_vjc_comp(tvbuff_t *tvb, packet_info *pinfo _U_, proto_tree *tree, void* data _U_) { /* A Van Jacobson compressed packet contains a change mask, which indicates * possible fields that may be present. */ proto_tree *subtree = NULL; proto_item *ti = NULL; unsigned hdr_len = 3; // See below bool hdr_error = false; unsigned ip_len = 0; unsigned pkt_len = 0; unsigned d_ipid = 0; unsigned d_seq = 0; unsigned d_ack = 0; int d_win = 0; uint8_t flags = 0; unsigned offset = 0; uint32_t urg = 0; uint32_t ip_chksum = 0; uint32_t tcp_chksum = 0; uint32_t vjc_cnum = 0; conversation_t *conv = NULL; vjc_hdr_t *this_hdr = NULL; vjc_hdr_t *last_hdr = NULL; vjc_conv_t *pkt_data = NULL; uint8_t *pdata = NULL; tvbuff_t *tcpip_tvb = NULL; tvbuff_t *sub_tvb = NULL; /* Calculate the length of the VJC header, * accounting for extensions in the delta fields. * We start with a value of 3, because we'll always have * an 8-bit change mask and a 16-bit TCP checksum. */ #define TEST_HDR_LEN \ if (hdr_len > tvb_captured_length(tvb)) { hdr_error = true; goto done_header_len; } TEST_HDR_LEN; flags = tvb_get_uint8(tvb, offset); if (flags & VJC_FLAG_C) { // have connection number hdr_len++; TEST_HDR_LEN; } if ((flags & VJC_FLAGS_SAWU) == VJC_FLAGS_SAWU) { /* Special case for "unidirectional data transfer". * No change to header size; d_ack = 0, and * we're to calculate d_seq ourselves. */ } else if ((flags & VJC_FLAGS_SAWU) == VJC_FLAGS_SWU) { /* Special case for "echoed interactive traffic". * No change to header size; we're to calculate d_seq and d_ack. */ } else { /* Not a special case, determine the header size by * testing the SAWU flags individually. */ if (flags & VJC_FLAG_U) { // have urgent pointer hdr_len += 2; TEST_HDR_LEN; } if (flags & VJC_FLAG_W) { // have d_win if (0 == tvb_get_int8(tvb, offset + hdr_len)) hdr_len += 3; else hdr_len++; TEST_HDR_LEN; } if (flags & VJC_FLAG_A) { // have d_ack if (0 == tvb_get_uint8(tvb, offset + hdr_len)) hdr_len += 3; else hdr_len++; TEST_HDR_LEN; } if (flags & VJC_FLAG_S) { // have d_seq if (0 == tvb_get_uint8(tvb, offset + hdr_len)) hdr_len += 3; else hdr_len++; TEST_HDR_LEN; } } if (flags & VJC_FLAG_I) { // have IP ID if (0 == tvb_get_uint8(tvb, offset + hdr_len)) hdr_len += 3; else hdr_len++; TEST_HDR_LEN; } /* Now that we have the header length, use it when assigning the * protocol item. */ #undef TEST_HDR_LEN done_header_len: ti = proto_tree_add_item(tree, proto_vjc, tvb, 0, MIN(hdr_len, tvb_captured_length(tvb)), ENC_NA); subtree = proto_item_add_subtree(ti, ett_vjc); proto_item_set_text(subtree, "PPP Van Jacobson compressed TCP/IP"); if (hdr_error) { proto_tree_add_expert_format(subtree, pinfo, &ei_vjc_bad_data, tvb, 0, -1, "Packet truncated, compression header incomplete"); return tvb_captured_length(tvb); } ti = proto_tree_add_boolean(subtree, hf_vjc_comp, tvb, 0, 0, true); proto_item_set_generated(ti); proto_tree_add_bitmask(subtree, tvb, 0, hf_vjc_change_mask, ett_vjc_change_mask, vjc_change_mask_fields, ENC_NA); if ((flags & VJC_FLAGS_SAWU) == VJC_FLAGS_SAWU) { proto_tree_add_expert(subtree, pinfo, &ei_vjc_sawu, tvb, 0, 1); } else if ((flags & VJC_FLAGS_SAWU) == VJC_FLAGS_SWU) { proto_tree_add_expert(subtree, pinfo, &ei_vjc_swu, tvb, 0, 1); } offset++; if (flags & VJC_FLAG_C) { proto_tree_add_item_ret_uint(subtree, hf_vjc_cnum, tvb, offset, 1, ENC_BIG_ENDIAN, &vjc_cnum); last_cnum = vjc_cnum; offset++; } else { vjc_cnum = last_cnum; if (vjc_cnum != CNUM_INVALID) { ti = proto_tree_add_uint(subtree, hf_vjc_cnum, tvb, offset, 0, vjc_cnum); proto_item_set_generated(ti); } else { proto_tree_add_expert(subtree, pinfo, &ei_vjc_no_cnum, tvb, 0, 0); } } conv = vjc_find_conversation(pinfo, vjc_cnum, false); if (NULL != conv) { pkt_data = (vjc_conv_t *)conversation_get_proto_data(conv, proto_vjc); // Will be testing that pkt_data exists below } else { proto_tree_add_expert(subtree, pinfo, &ei_vjc_no_conversation, tvb, 1, (flags & VJC_FLAG_C) ? 1 : 0); } proto_tree_add_item_ret_uint(subtree, hf_vjc_chksum, tvb, offset, 2, ENC_BIG_ENDIAN, &tcp_chksum); offset += 2; if ((flags & VJC_FLAGS_SAWU) == VJC_FLAGS_SAWU) { /* Special case for "unidirectional data transfer". * d_ack is 0, and d_seq changed by the amount of data in the previous packet. */ flags &= ~VJC_FLAGS_SAWU; d_ack = 0; if (NULL != pkt_data) { d_seq = pkt_data->last_frame_len; } ti = proto_tree_add_uint(subtree, hf_vjc_d_ack, tvb, offset, 0, d_ack); proto_item_set_generated(ti); ti = proto_tree_add_uint(subtree, hf_vjc_d_seq, tvb, offset, 0, d_seq); proto_item_set_generated(ti); } else if ((flags & VJC_FLAGS_SAWU) == VJC_FLAGS_SWU) { /* Special case for "echoed interactive traffic". * d_seq and d_ack changed by the amount of user data in the * previous packet. */ flags &= ~VJC_FLAGS_SAWU; if (NULL != pkt_data) { d_seq = d_ack = pkt_data->last_frame_len; } ti = proto_tree_add_uint(subtree, hf_vjc_d_ack, tvb, offset, 0, d_ack); proto_item_set_generated(ti); ti = proto_tree_add_uint(subtree, hf_vjc_d_seq, tvb, offset, 0, d_seq); proto_item_set_generated(ti); } else { /* Not a special case, read the SAWU flags individually */ if (flags & VJC_FLAG_U) { /* "The packet’s urgent pointer is sent if URG is set ..." * I assume that means the full 16-bit value here. */ proto_tree_add_item_ret_uint(subtree, hf_vjc_urg, tvb, offset, 2, ENC_BIG_ENDIAN, &urg); offset += 2; } else { urg = 0; } if (flags & VJC_FLAG_W) { /* "The number sent for the window is also the difference between the current * and previous values. However, either positive or negative changes are * allowed since the window is a 16-bit field." */ d_win = vjc_delta_int(subtree, hf_vjc_d_win, tvb, &offset); } else { d_win = 0; } /* The rest of the deltas can only be positive. */ if (flags & VJC_FLAG_A) { d_ack = vjc_delta_uint(subtree, hf_vjc_d_ack, tvb, &offset); } else { d_ack = 0; } if (flags & VJC_FLAG_S) { d_seq = vjc_delta_uint(subtree, hf_vjc_d_seq, tvb, &offset); } else { d_seq = 0; } } if (flags & VJC_FLAG_I) { d_ipid = vjc_delta_uint(subtree, hf_vjc_d_ipid, tvb, &offset); } else { /* "However, unlike the rest of the compressed fields, the assumed * change when I is clear is one, not zero." - section 3.2.2 */ d_ipid = 1; ti = proto_tree_add_uint(subtree, hf_vjc_d_ipid, tvb, offset, 0, d_ipid); proto_item_set_generated(ti); } if (!(pinfo->p2p_dir == P2P_DIR_RECV || pinfo->p2p_dir == P2P_DIR_SENT)) { /* We can't make a proper conversation if we don't know the endpoints */ proto_tree_add_expert(subtree, pinfo, &ei_vjc_no_direction, tvb, offset, tvb_captured_length_remaining(tvb, offset)); return tvb_captured_length(tvb); } if (NULL == conv) { proto_tree_add_expert(subtree, pinfo, &ei_vjc_undecoded, tvb, offset, tvb_captured_length_remaining(tvb, offset)); return tvb_captured_length(tvb); } if (NULL == pkt_data) { proto_tree_add_expert(subtree, pinfo, &ei_vjc_no_conv_data, tvb, offset, tvb_captured_length_remaining(tvb, offset)); return tvb_captured_length(tvb); } if (!pinfo->fd->visited) { /* We haven't visited this packet before. * Form its vjc_hdr_t from the deltas and the info from the previous frame. */ last_hdr = (vjc_hdr_t *)wmem_map_lookup(pkt_data->vals, GUINT_TO_POINTER(pkt_data->last_frame)); if (NULL != last_hdr) { this_hdr = wmem_new0(wmem_file_scope(), vjc_hdr_t); this_hdr->tcp_chksum = (uint16_t)tcp_chksum; this_hdr->urg = (uint16_t)urg; this_hdr->win = last_hdr->win + d_win; this_hdr->seq = last_hdr->seq + d_seq; this_hdr->ack = last_hdr->ack + d_ack; this_hdr->ip_id = last_hdr->ip_id + d_ipid; this_hdr->psh = (flags & VJC_FLAG_P) == VJC_FLAG_P; wmem_map_insert(pkt_data->vals, GUINT_TO_POINTER(pinfo->num), this_hdr); // This frame is the next frame's last frame pkt_data->last_frame = pinfo->num; pkt_data->last_frame_len = tvb_reported_length_remaining(tvb, offset); } else { proto_tree_add_expert_format(subtree, pinfo, &ei_vjc_error, tvb, 0, 0, "Dissector error: unable to find headers for prior frame %d", pkt_data->last_frame); return tvb_captured_length(tvb); } // if last_hdr is null, then this_hdr will stay null and be handled below } else { /* We have visited this packet before. * Get the values we saved the first time. */ this_hdr = (vjc_hdr_t *)wmem_map_lookup(pkt_data->vals, GUINT_TO_POINTER(pinfo->num)); } if (NULL != this_hdr) { /* pkt_data->frame_headers is our template packet header data. * Apply changes to it as needed. * The changes are intentionally done in the template before copying. */ pkt_len = pkt_data->header_len + tvb_reported_length_remaining(tvb, offset); pdata = pkt_data->frame_headers; /* shorthand */ ip_len = (pdata[0] & 0x0F) << 2; /* IP length */ PUT_16(pdata, 2, pkt_len); /* IP ID */ PUT_16(pdata, 4, this_hdr->ip_id); /* IP checksum */ PUT_16(pdata, 10, 0x0000); ip_chksum = ip_checksum(pdata, ip_len); PUT_16(pdata, 10, g_htons(ip_chksum)); /* TCP seq */ PUT_32(pdata, ip_len + 4, this_hdr->seq); /* TCP ack */ PUT_32(pdata, ip_len + 8, this_hdr->ack); /* TCP window */ PUT_16(pdata, ip_len + 14, this_hdr->win); /* TCP push */ if (this_hdr->psh) { pdata[ip_len + 13] |= 0x08; } else { pdata[ip_len + 13] &= ~0x08; } /* TCP checksum */ PUT_16(pdata, ip_len + 16, this_hdr->tcp_chksum); /* TCP urg */ if (this_hdr->urg) { pdata[ip_len + 13] |= 0x20; PUT_16(pdata, ip_len + 18, this_hdr->urg); } else { pdata[ip_len + 13] &= ~0x20; PUT_16(pdata, ip_len + 18, 0x0000); } /* Now that we're done manipulating the packet header, stick it into * a TVB for sub-dissectors to use. */ sub_tvb = tvb_new_child_real_data(tvb, pdata, pkt_data->header_len, pkt_data->header_len); tvb_set_free_cb(sub_tvb, NULL); // Reuse pkt_len pkt_len = tvb_captured_length_remaining(tvb, offset); if (0 < pkt_len) { tcpip_tvb = tvb_new_composite(); tvb_composite_append(tcpip_tvb, sub_tvb); tvb_composite_append(tcpip_tvb, tvb_new_subset_remaining(tvb, offset)); tvb_composite_finalize(tcpip_tvb); ti = proto_tree_add_item(subtree, hf_vjc_tcpdata, tvb, offset, pkt_len, ENC_NA); proto_item_set_text(ti, "TCP data (%d byte%s)", pkt_len, plurality(pkt_len, "", "s")); } else { tcpip_tvb = sub_tvb; } add_new_data_source(pinfo, tcpip_tvb, "Decompressed TCP/IP data"); return offset + call_dissector_with_data(ip_handle, tcpip_tvb, pinfo, tree, data); } else { proto_tree_add_expert_format(subtree, pinfo, &ei_vjc_error, tvb, 0, 0, "Dissector error: unable to find headers for current frame %d", pinfo->num); } return tvb_captured_length(tvb); } void proto_register_vjc(void) { static hf_register_info hf[] = { { &hf_vjc_comp, { "Is compressed", "vjc.compressed", FT_BOOLEAN, BASE_NONE, NULL, 0x0, NULL, HFILL }}, { &hf_vjc_cnum, { "Connection number", "vjc.connection_number", FT_UINT8, BASE_DEC, NULL, 0x0, NULL, HFILL }}, { &hf_vjc_change_mask, { "Change mask", "vjc.change_mask", FT_UINT8, BASE_HEX, NULL, 0x0, NULL, HFILL }}, { &hf_vjc_change_mask_r, { "Reserved", "vjc.change_mask.reserved", FT_BOOLEAN, 8, TFS(&tfs_set_notset), VJC_FLAG_R, "Undefined bit", HFILL }}, { &hf_vjc_change_mask_c, { "Connection number flag", "vjc.change_mask.connection_number", FT_BOOLEAN, 8, TFS(&tfs_set_notset), VJC_FLAG_C, "Whether connection number is present", HFILL }}, { &hf_vjc_change_mask_i, { "IP ID flag", "vjc.change_mask.ip_id", FT_BOOLEAN, 8, TFS(&tfs_set_notset), VJC_FLAG_I, "Whether IP ID is present", HFILL }}, { &hf_vjc_change_mask_p, { "TCP PSH flag", "vjc.change_mask.psh", FT_BOOLEAN, 8, TFS(&tfs_set_notset), VJC_FLAG_P, "Whether to set TCP PSH", HFILL }}, { &hf_vjc_change_mask_s, { "TCP Sequence flag", "vjc.change_mask.seq", FT_BOOLEAN, 8, TFS(&tfs_set_notset), VJC_FLAG_S, "Whether TCP SEQ is present", HFILL }}, { &hf_vjc_change_mask_a, { "TCP Acknowledgement flag", "vjc.change_mask.ack", FT_BOOLEAN, 8, TFS(&tfs_set_notset), VJC_FLAG_A, "Whether TCP ACK is present", HFILL }}, { &hf_vjc_change_mask_w, { "TCP Window flag", "vjc.change_mask.win", FT_BOOLEAN, 8, TFS(&tfs_set_notset), VJC_FLAG_W, "Whether TCP Window is present", HFILL }}, { &hf_vjc_change_mask_u, { "TCP Urgent flag", "vjc.change_mask.urg", FT_BOOLEAN, 8, TFS(&tfs_set_notset), VJC_FLAG_U, "Whether TCP URG pointer is present", HFILL }}, { &hf_vjc_chksum, { "TCP Checksum", "vjc.checksum", FT_UINT16, BASE_HEX, NULL, 0x0, "TCP checksum of original packet", HFILL}}, { &hf_vjc_urg, { "Urgent pointer", "vjc.urgent_pointer", FT_UINT16, BASE_DEC, NULL, 0x0, "TCP urgent pointer of original packet", HFILL}}, { &hf_vjc_d_win, { "Delta window", "vjc.delta_window", FT_INT16, BASE_DEC, NULL, 0x0, "Change in TCP window size from previous packet", HFILL}}, { &hf_vjc_d_ack, { "Delta ack", "vjc.delta_ack", FT_UINT16, BASE_DEC, NULL, 0x0, "Change in TCP acknowledgement number from previous packet", HFILL}}, { &hf_vjc_d_seq, { "Delta seq", "vjc.delta_seq", FT_UINT16, BASE_DEC, NULL, 0x0, "Change in TCP sequence number from previous packet", HFILL}}, { &hf_vjc_d_ipid, { "Delta IP ID", "vjc.delta_ipid", FT_UINT16, BASE_DEC, NULL, 0x0, "Change in IP Identification number from previous packet", HFILL}}, { &hf_vjc_tcpdata, { "TCP data", "vjc.tcp_data", FT_BYTES, BASE_NONE, NULL, 0x0, "Original TCP payload", HFILL}}, }; static int *ett[] = { &ett_vjc, &ett_vjc_change_mask, }; expert_module_t* expert_vjc; static ei_register_info ei[] = { { &ei_vjc_sawu, { "vjc.special.sawu", PI_PROTOCOL, PI_CHAT, ".... 1111 = special case for \"unidirectional data transfer\"", EXPFILL }}, { &ei_vjc_swu, { "vjc.special.swu", PI_PROTOCOL, PI_CHAT, ".... 1011 = special case for \"echoed interactive traffic\"", EXPFILL }}, { &ei_vjc_no_cnum, { "vjc.no_connection_id", PI_PROTOCOL, PI_WARN, "No connection ID and no prior connection (common at capture start)", EXPFILL }}, { &ei_vjc_no_conversation, { "vjc.no_connection", PI_PROTOCOL, PI_WARN, "No saved connection found (common at capture start)", EXPFILL }}, { &ei_vjc_no_direction, { "vjc.no_direction", PI_UNDECODED, PI_WARN, "Connection has no direction info, cannot decompress", EXPFILL }}, { &ei_vjc_no_conv_data, { "vjc.no_connection_data", PI_UNDECODED, PI_WARN, "Could not find saved connection data", EXPFILL }}, { &ei_vjc_undecoded, { "vjc.no_decompress", PI_UNDECODED, PI_WARN, "Undecoded data (impossible due to missing information)", EXPFILL }}, { &ei_vjc_bad_data, { "vjc.bad_data", PI_PROTOCOL, PI_ERROR, "Non-compliant packet data", EXPFILL }}, { &ei_vjc_error, { "vjc.error", PI_MALFORMED, PI_ERROR, "Unrecoverable dissector error", EXPFILL }}, }; proto_vjc = proto_register_protocol("Van Jacobson PPP compression", "VJC", "vjc"); proto_register_field_array(proto_vjc, hf, array_length(hf)); proto_register_subtree_array(ett, array_length(ett)); expert_vjc = expert_register_protocol(proto_vjc); expert_register_field_array(expert_vjc, ei, array_length(ei)); vjcc_handle = register_dissector("vjc_compressed", dissect_vjc_comp, proto_vjc); vjcu_handle = register_dissector("vjc_uncompressed", dissect_vjc_uncomp, proto_vjc); register_init_routine(&vjc_init_protocol); register_cleanup_routine(&vjc_cleanup_protocol); } void proto_reg_handoff_vjc(void) { ip_handle = find_dissector("ip"); dissector_add_uint("ppp.protocol", PPP_VJC_COMP, vjcc_handle); dissector_add_uint("ppp.protocol", PPP_VJC_UNCOMP, vjcu_handle); } /* * Editor modelines - https://www.wireshark.org/tools/modelines.html * * Local variables: * c-basic-offset: 4 * tab-width: 8 * indent-tabs-mode: nil * End: * * vi: set shiftwidth=4 tabstop=8 expandtab: * :indentSize=4:tabSize=8:noTabs=true: */