/*************************************************************************** * TCPHeader.cc -- The TCPHeader Class represents a TCP packet. It * * contains methods to set the different header fields. These methods * * tipically perform the necessary error checks and byte order * * conversions. * * * ***********************IMPORTANT NMAP LICENSE TERMS************************ * * * The Nmap Security Scanner is (C) 1996-2012 Insecure.Com LLC. Nmap is * * also a registered trademark of Insecure.Com LLC. This program is free * * software; you may redistribute and/or modify it under the terms of the * * GNU General Public License as published by the Free Software * * Foundation; Version 2 with the clarifications and exceptions described * * below. This guarantees your right to use, modify, and redistribute * * this software under certain conditions. If you wish to embed Nmap * * technology into proprietary software, we sell alternative licenses * * (contact sales@insecure.com). Dozens of software vendors already * * license Nmap technology such as host discovery, port scanning, OS * * detection, version detection, and the Nmap Scripting Engine. * * * * Note that the GPL places important restrictions on "derived works", yet * * it does not provide a detailed definition of that term. To avoid * * misunderstandings, we interpret that term as broadly as copyright law * * allows. For example, we consider an application to constitute a * * "derivative work" for the purpose of this license if it does any of the * * following: * * o Integrates source code from Nmap * * o Reads or includes Nmap copyrighted data files, such as * * nmap-os-db or nmap-service-probes. * * o Executes Nmap and parses the results (as opposed to typical shell or * * execution-menu apps, which simply display raw Nmap output and so are * * not derivative works.) * * o Integrates/includes/aggregates Nmap into a proprietary executable * * installer, such as those produced by InstallShield. * * o Links to a library or executes a program that does any of the above * * * * The term "Nmap" should be taken to also include any portions or derived * * works of Nmap, as well as other software we distribute under this * * license such as Zenmap, Ncat, and Nping. This list is not exclusive, * * but is meant to clarify our interpretation of derived works with some * * common examples. Our interpretation applies only to Nmap--we don't * * speak for other people's GPL works. * * * * If you have any questions about the GPL licensing restrictions on using * * Nmap in non-GPL works, we would be happy to help. As mentioned above, * * we also offer alternative license to integrate Nmap into proprietary * * applications and appliances. These contracts have been sold to dozens * * of software vendors, and generally include a perpetual license as well * * as providing for priority support and updates. They also fund the * * continued development of Nmap. Please email sales@insecure.com for * * further information. * * * * As a special exception to the GPL terms, Insecure.Com LLC grants * * permission to link the code of this program with any version of the * * OpenSSL library which is distributed under a license identical to that * * listed in the included docs/licenses/OpenSSL.txt file, and distribute * * linked combinations including the two. You must obey the GNU GPL in all * * respects for all of the code used other than OpenSSL. If you modify * * this file, you may extend this exception to your version of the file, * * but you are not obligated to do so. * * * * If you received these files with a written license agreement or * * contract stating terms other than the terms above, then that * * alternative license agreement takes precedence over these comments. * * * * Source is provided to this software because we believe users have a * * right to know exactly what a program is going to do before they run it. * * This also allows you to audit the software for security holes (none * * have been found so far). * * * * Source code also allows you to port Nmap to new platforms, fix bugs, * * and add new features. You are highly encouraged to send your changes * * to nmap-dev@insecure.org for possible incorporation into the main * * distribution. By sending these changes to Fyodor or one of the * * Insecure.Org development mailing lists, or checking them into the Nmap * * source code repository, it is understood (unless you specify otherwise) * * that you are offering the Nmap Project (Insecure.Com LLC) the * * unlimited, non-exclusive right to reuse, modify, and relicense the * * code. Nmap will always be available Open Source, but this is important * * because the inability to relicense code has caused devastating problems * * for other Free Software projects (such as KDE and NASM). We also * * occasionally relicense the code to third parties as discussed above. * * If you wish to specify special license conditions of your * * contributions, just say so when you send them. * * * * This program is distributed in the hope that it will be useful, but * * WITHOUT ANY WARRANTY; without even the implied warranty of * * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * * General Public License v2.0 for more details at * * http://www.gnu.org/licenses/gpl-2.0.html , or in the COPYING file * * included with Nmap. * * * ***************************************************************************/ /* This code was originally part of the Nping tool. */ #include "TCPHeader.h" #include /******************************************************************************/ /* CONTRUCTORS, DESTRUCTORS AND INITIALIZATION METHODS */ /******************************************************************************/ TCPHeader::TCPHeader(){ this->reset(); } /* End of TCPHeader constructor */ TCPHeader::~TCPHeader(){ } /* End of TCPHeader destructor */ /** Sets every attribute to its default value */ void TCPHeader::reset(){ memset(&this->h, 0, sizeof(nping_tcp_hdr_t)); this->length=TCP_HEADER_LEN; /* Initial value 20. This will be incremented if options are used */ this->tcpoptlen=0; this->setSourcePort(TCP_DEFAULT_SPORT); this->setDestinationPort(TCP_DEFAULT_DPORT); this->setSeq(TCP_DEFAULT_SEQ); this->setAck(TCP_DEFAULT_ACK); this->setFlags(TCP_DEFAULT_FLAGS); this->setWindow(TCP_DEFAULT_WIN); this->setUrgPointer(TCP_DEFAULT_URP); this->setOffset(); } /* End of reset() */ /******************************************************************************/ /* PacketElement:: OVERWRITTEN METHODS */ /******************************************************************************/ /** @warning This method is essential for the superclass getBinaryBuffer() * method to work. Do NOT change a thing unless you know what you're doing */ u8 * TCPHeader::getBufferPointer(){ return (u8*)(&h); } /* End of getBufferPointer() */ /** Stores supplied packet in the internal buffer so the information * can be accessed using the standard get & set methods. * @warning The TCPHeader class is able to hold a maximum of 60 bytes. If the * supplied buffer is longer than that, only the first 60 bytes will be stored * in the internal buffer. * @warning Supplied len MUST be at least 20 bytes (min TCP header length). * @return OP_SUCCESS on success and OP_FAILURE in case of error */ int TCPHeader::storeRecvData(const u8 *buf, size_t len){ if(buf==NULL || lenreset(); /* Re-init the object, just in case the caller had used it already */ this->length=stored_len; if(stored_len>TCP_HEADER_LEN) this->tcpoptlen=stored_len-TCP_HEADER_LEN; memcpy(&(this->h), buf, stored_len); } return OP_SUCCESS; } /* End of storeRecvData() */ /* Returns a protocol identifier. This is used by packet parsing funtions * that return linked lists of PacketElement objects, to determine the protocol * the object represents. */ int TCPHeader::protocol_id() const { return HEADER_TYPE_TCP; } /* End of protocol_id() */ /** Determines if the data stored in the object after an storeRecvData() call * is valid and safe to use. This mainly checks the length of the data but may * also test the value of certain protocol fields to ensure their correctness. * @warning If the information stored in the object has been set through a * call to storeRecvData(), the object's internal length count may be updated * if the validation is successful. * @return the length, in bytes, of the header, if its found to be valid or * OP_FAILURE (-1) otherwise. */ int TCPHeader::validate(){ if(this->getOffset()<5) return OP_FAILURE; else if(this->getOffset()*4 > this->length) return OP_FAILURE; this->length=this->getOffset()*4; return this->length; } /* End of validate() */ /** Prints the contents of the header and calls print() on the next protocol * header in the chain (if there is any). * @return OP_SUCCESS on success and OP_FAILURE in case of error. */ int TCPHeader::print(FILE *output, int detail) const { char optinfo[256]; fprintf(output, "TCP["); fprintf(output, "%d", this->getSourcePort()); fprintf(output, " >"); fprintf(output, " %d", this->getDestinationPort()); fprintf(output, " %s%s%s%s%s%s%s%s", !this->getSYN() ? "" : "S", !this->getFIN() ? "" : "F", !this->getRST() ? "" : "R", !this->getPSH() ? "" : "P", !this->getACK() ? "" : "A", !this->getURG() ? "" : "U", !this->getECN() ? "" : "E", !this->getCWR() ? "" : "C" ); fprintf(output, " seq=%lu", (long unsigned int)this->getSeq() ); if(detail>=PRINT_DETAIL_HIGH){ fprintf(output, " ack=%lu", (long unsigned int)this->getAck() ); fprintf(output, " off=%d", this->getOffset() ); fprintf(output, " res=%d", this->h.th_x2); } fprintf(output, " win=%hu", this->getWindow() ); if(detail>=PRINT_DETAIL_MED) fprintf(output, " csum=0x%04X", ntohs( this->getSum() )); if(detail>=PRINT_DETAIL_HIGH) fprintf(output, " urp=%d", this->getUrgPointer() ); if(this->tcpoptlen>0 && (this->length >= TCP_HEADER_LEN+this->tcpoptlen) && this->tcpoptlen<=MAX_TCP_OPTIONS_LEN){ this->__tcppacketoptinfo(this->h.options, this->tcpoptlen, optinfo, sizeof(optinfo)-1); optinfo[255]='\0'; fprintf(output, " %s", optinfo); } fprintf(output, "]"); if(this->next!=NULL){ print_separator(output, detail); next->print(output, detail); } return OP_SUCCESS; } /* End of print() */ /* Get an ASCII information about a tcp option which is pointed by optp, with a length of len. The result is stored in the result buffer. The result may look like "" */ void TCPHeader::__tcppacketoptinfo(const u8 *optp, int len, char *result, int bufsize) const { assert(optp); assert(result); char *p, ch; const u8 *q; int opcode; u16 tmpshort; u32 tmpword1, tmpword2; unsigned int i=0; p = result; *p = '\0'; q = optp; ch = '<'; while (len > 0 && bufsize > 2) { Snprintf(p, bufsize, "%c", ch); bufsize--; p++; opcode = *q++; if (!opcode) { /* End of List */ Snprintf(p, bufsize, "eol"); bufsize -= strlen(p); p += strlen(p); len--; } else if (opcode == 1) { /* No Op */ Snprintf(p, bufsize, "nop"); bufsize -= strlen(p); p += strlen(p); len--; } else if (opcode == 2) { /* MSS */ if (len < 4) break; /* MSS has 4 bytes */ q++; memcpy(&tmpshort, q, 2); Snprintf(p, bufsize, "mss %u", ntohs(tmpshort)); bufsize -= strlen(p); p += strlen(p); q += 2; len -= 4; } else if (opcode == 3) { /* Window Scale */ if (len < 3) break; /* Window Scale option has 3 bytes */ q++; Snprintf(p, bufsize, "wscale %u", *q); bufsize -= strlen(p); p += strlen(p); q++; len -= 3; } else if (opcode == 4) { /* SACK permitted */ if (len < 2) break; /* SACK permitted option has 2 bytes */ Snprintf(p, bufsize, "sackOK"); bufsize -= strlen(p); p += strlen(p); q++; len -= 2; } else if (opcode == 5) { /* SACK */ unsigned sackoptlen = *q; if ((unsigned) len < sackoptlen) break; /* This would break parsing, so it's best to just give up */ if (sackoptlen < 2) break; q++; if ((sackoptlen - 2) == 0 || ((sackoptlen - 2) % 8 != 0)) { Snprintf(p, bufsize, "malformed sack"); bufsize -= strlen(p); p += strlen(p); } else { Snprintf(p, bufsize, "sack %d ", (sackoptlen - 2) / 8); bufsize -= strlen(p); p += strlen(p); for (i = 0; i < sackoptlen - 2; i += 8) { memcpy(&tmpword1, q + i, 4); memcpy(&tmpword2, q + i + 4, 4); Snprintf(p, bufsize, "{%u:%u}", tmpword1, tmpword2); bufsize -= strlen(p); p += strlen(p); } } q += sackoptlen - 2; len -= sackoptlen; } else if (opcode == 8) { /* Timestamp */ if (len < 10) break; /* Timestamp option has 10 bytes */ q++; memcpy(&tmpword1, q, 4); memcpy(&tmpword2, q + 4, 4); Snprintf(p, bufsize, "timestamp %u %u", ntohl(tmpword1), ntohl(tmpword2)); bufsize -= strlen(p); p += strlen(p); q += 8; len -= 10; } ch = ','; } if (len > 0) { *result = '\0'; return; } Snprintf(p, bufsize, ">"); } /******************************************************************************/ /* PROTOCOL-SPECIFIC METHODS */ /******************************************************************************/ /** Sets source port. * @warning Port must be supplied in host byte order. This method performs * byte order conversion using htons() */ int TCPHeader::setSourcePort(u16 p){ h.th_sport = htons(p); return OP_SUCCESS; } /* End of setSourcePort() */ /** Returns source port in HOST byte order */ u16 TCPHeader::getSourcePort() const { return ntohs(h.th_sport); } /* End of getSourcePort() */ /** Sets destination port. * @warning Port must be supplied in host byte order. This method performs * byte order conversion using htons() */ int TCPHeader::setDestinationPort(u16 p){ h.th_dport = htons(p); return OP_SUCCESS; } /* End of setDestinationPort() */ /** Returns destination port in HOST byte order */ u16 TCPHeader::getDestinationPort() const { return ntohs(h.th_dport); } /* End of getDestinationPort() */ /** Sets sequence number. * @warning Seq number must be supplied in host byte order. This method * performs byte order conversion using htonl() */ int TCPHeader::setSeq(u32 p){ h.th_seq = htonl(p); return OP_SUCCESS; } /* End of setSeq() */ /** Returns sequence number in HOST byte order */ u32 TCPHeader::getSeq() const { return ntohl(h.th_seq); } /* End of getSeq() */ /** Sets acknowledgement number. * @warning ACK number must be supplied in host byte order. This method * performs byte order conversion using htonl() */ int TCPHeader::setAck(u32 p){ h.th_ack = htonl(p); return OP_SUCCESS; } /* End of setAck() */ /** Returns ACK number in HOST byte order */ u32 TCPHeader::getAck() const { return ntohl(h.th_ack); } /* End of getAck() */ /* TODO: Test this method. It may not work becuasse th_off is supposed to * be 4 bits long and arg o is 8. * UPDATE: It seems to work just fine. However, let's keep this note just * in case problems arise. */ int TCPHeader::setOffset(u8 o){ h.th_off = o; return OP_SUCCESS; } /* End of setOffset() */ int TCPHeader::setOffset(){ h.th_off = 5 + tcpoptlen/4; return OP_SUCCESS; } /* End of setOffset() */ /** Returns offset value */ u8 TCPHeader::getOffset() const { return h.th_off; } /* End of getOffset() */ /* Sets the 4-bit reserved field (Note that there are not 4 reserved bits anymore * as RFC 3540 introduces a new TCP flag, so calling this will overwrite * the value of such flag. */ int TCPHeader::setReserved(u8 r){ h.th_x2 = r; return OP_SUCCESS; } u8 TCPHeader::getReserved() const { return h.th_x2; } /** Sets TCP flags */ int TCPHeader::setFlags(u8 f){ h.th_flags = f; return OP_SUCCESS; } /* End of setFlags() */ /** Returns the 8bit flags field of the TCP header */ u8 TCPHeader::getFlags() const { return h.th_flags; } /* End of getFlags() */ /* Returns the 16bit flags field of the TCP header. As RFC 3540 defines a new * flag (NS), we no longer can store all TCP flags in a single octet, so * this method returns the flags as a two-octet unsigned integer. */ u16 TCPHeader::getFlags16() const { /* Obtain the value of dataoff+reserved+flags in host byte order */ u16 field=ntohs(*(u16 *)(((u8 *)&this->h)+12)); /* Erase the contents of the data offset field */ field = field & 0x0FFF; return field; } /* End of getFlags16() */ /** Sets flag CWR * @return Previous state of the flag */ bool TCPHeader::setCWR(){ u8 prev = h.th_flags & TH_CWR; h.th_flags |= TH_CWR; return prev; } /* End of setCWR() */ /** Unsets flag CWR * @return Previous state of the flag */ bool TCPHeader::unsetCWR(){ u8 prev = h.th_flags & TH_CWR; h.th_flags ^= TH_CWR; return prev; } /* End of unsetCWR() */ /** Get CWR flag */ bool TCPHeader::getCWR() const { return h.th_flags & TH_CWR; } /* End of getCWR() */ /** Sets flag ECE/ECN * @return Previous state of the flag */ bool TCPHeader::setECE(){ u8 prev = h.th_flags & TH_ECN; h.th_flags |= TH_ECN; return prev; } /* End of setECE() */ /** Unsets flag ECE/ECN * @return Previous state of the flag */ bool TCPHeader::unsetECE(){ u8 prev = h.th_flags & TH_ECN; h.th_flags ^= TH_ECN; return prev; } /* End of unsetECE() */ /** Get CWR flag */ bool TCPHeader::getECE() const { return h.th_flags & TH_ECN; } /* End of getECE() */ /** Same as setECE() but with a different name since there are two possible * ways to call this flag * @return Previous state of the flag */ bool TCPHeader::setECN(){ u8 prev = h.th_flags & TH_ECN; h.th_flags |= TH_ECN; return prev; } /* End of setECN() */ /** Unsets flag ECE/ECN * @return Previous state of the flag */ bool TCPHeader::unsetECN(){ u8 prev = h.th_flags & TH_ECN; h.th_flags ^= TH_ECN; return prev; } /* End of unsetECN() */ /** Get ECN flag */ bool TCPHeader::getECN() const { return h.th_flags & TH_ECN; } /* End of getECN() */ /** Sets flag URG * @return Previous state of the flag */ bool TCPHeader::setURG(){ u8 prev = h.th_flags & TH_URG; h.th_flags |= TH_URG; return prev; } /* End of setURG() */ /** Unsets flag URG * @return Previous state of the flag */ bool TCPHeader::unsetURG(){ u8 prev = h.th_flags & TH_URG; h.th_flags ^= TH_URG; return prev; } /* End of unsetURG() */ /** Get URG flag */ bool TCPHeader::getURG() const { return h.th_flags & TH_URG; } /* End of getURG() */ /** Sets flag ACK * @return Previous state of the flag */ bool TCPHeader::setACK(){ u8 prev = h.th_flags & TH_ACK; h.th_flags |= TH_ACK; return prev; } /* End of setACK() */ /** Unsets flag ACK * @return Previous state of the flag */ bool TCPHeader::unsetACK(){ u8 prev = h.th_flags & TH_ACK; h.th_flags ^= TH_ACK; return prev; } /* End of unsetACK() */ /** Get ACK flag */ bool TCPHeader::getACK() const { return h.th_flags & TH_ACK; } /* End of getACK() */ /** Sets flag PSH * @return Previous state of the flag */ bool TCPHeader::setPSH(){ u8 prev = h.th_flags & TH_PSH; h.th_flags |= TH_PSH; return prev; } /* End of setPSH() */ /** Unsets flag PSH * @return Previous state of the flag */ bool TCPHeader::unsetPSH(){ u8 prev = h.th_flags & TH_PSH; h.th_flags ^= TH_PSH; return prev; } /* End of unsetPSH() */ /** Get PSH flag */ bool TCPHeader::getPSH() const { return h.th_flags & TH_PSH; } /* End of getPSH() */ /** Sets flag RST * @return Previous state of the flag */ bool TCPHeader::setRST(){ u8 prev = h.th_flags & TH_RST; h.th_flags |= TH_RST; return prev; } /* End of setRST() */ /** Unsets flag RST * @return Previous state of the flag */ bool TCPHeader::unsetRST(){ u8 prev = h.th_flags & TH_RST; h.th_flags ^= TH_RST; return prev; } /* End of unsetRST() */ /** Get RST flag */ bool TCPHeader::getRST() const { return h.th_flags & TH_RST; } /* End of getRST() */ /** Sets flag SYN * @return Previous state of the flag */ bool TCPHeader::setSYN(){ u8 prev = h.th_flags & TH_SYN; h.th_flags |= TH_SYN; return prev; } /* End of setSYN() */ /** Unsets flag SYN * @return Previous state of the flag */ bool TCPHeader::unsetSYN(){ u8 prev = h.th_flags & TH_SYN; h.th_flags ^= TH_SYN; return prev; } /* End of unsetSYN() */ /** Get SYN flag */ bool TCPHeader::getSYN() const { return h.th_flags & TH_SYN; } /* End of getSYN() */ /** Sets flag FIN * @return Previous state of the flag */ bool TCPHeader::setFIN(){ u8 prev = h.th_flags & TH_FIN; h.th_flags |= TH_FIN; return prev; } /* End of setFIN() */ /** Unsets flag FIN * @return Previous state of the flag */ bool TCPHeader::unsetFIN(){ u8 prev = h.th_flags & TH_FIN; h.th_flags ^= TH_FIN; return prev; } /* End of unsetFIN() */ /** Get FIN flag */ bool TCPHeader::getFIN() const { return h.th_flags & TH_FIN; } /* End of getFIN() */ /** Sets window size. * @warning Win number must be supplied in host byte order. This method * performs byte order conversion using htons() */ int TCPHeader::setWindow(u16 p){ h.th_win = htons(p); return OP_SUCCESS; } /* End of setWindow() */ /** Returns window size in HOST byte order. */ u16 TCPHeader::getWindow() const { return ntohs(h.th_win); } /* End of getWindow() */ /** Sets urgent pointer. * @warning Pointer must be supplied in host byte order. This method * performs byte order conversion using htons() */ int TCPHeader::setUrgPointer(u16 l){ h.th_urp = htons(l); return OP_SUCCESS; } /* End of setUrgPointer() */ /** Returns Urgent Pointer in HOST byte order. */ u16 TCPHeader::getUrgPointer() const { return ntohs(h.th_urp); } /* End of getUrgPointer() */ int TCPHeader::setSum(struct in_addr src, struct in_addr dst){ int bufflen; u8 aux[ MAX_TCP_PAYLOAD_LEN ]; /* FROM: RFC 1323: TCP Extensions for High Performance, March 4, 2009 * * "With IP Version 4, the largest amount of TCP data that can be sent in * a single packet is 65495 bytes (64K - 1 - size of fixed IP and TCP * headers)". * * In theory TCP should not worry about the practical max payload length * because it is supposed to be independent of the network layer. However, * since TCP does not have any length field and we need to allocate a * buffer, we are using that value. (Note htat in UDPHeader.cc we do just * the opposite, forget about the practical limitation and allow the * theorical limit for the payload. */ h.th_sum = 0; /* Copy packet contents to a buffer */ bufflen=dumpToBinaryBuffer(aux, MAX_TCP_PAYLOAD_LEN); /* Compute checksum */ h.th_sum = ipv4_pseudoheader_cksum(&src, &dst, IPPROTO_TCP, bufflen, (char *)aux); return OP_SUCCESS; } /* End of setSum() */ /** @warning Sum is set to supplied value with NO byte ordering conversion * performed. */ int TCPHeader::setSum(u16 s){ h.th_sum = s; return OP_SUCCESS; } /* End of setSum() */ int TCPHeader::setSum(){ this->h.th_sum=0; this->h.th_sum = this->compute_checksum(); return OP_SUCCESS; } /* End of setSum() */ /** Set the TCP checksum field to a random value, which may accidentally * match the correct checksum */ int TCPHeader::setSumRandom(){ h.th_sum=get_random_u16(); return OP_SUCCESS; } /* End of setSumRandom() */ /** Set the TCP checksum field to a random value. It takes the source and * destination address to make sure the random generated sum does not * accidentally match the correct checksum. This function only handles * IPv4 address. */ int TCPHeader::setSumRandom(struct in_addr source, struct in_addr destination){ u16 correct_csum=0; /* Compute the correct checksum */ this->setSum(source, destination); correct_csum=this->getSum(); /* Generate numbers until one does not match the correct sum */ while( (h.th_sum=get_random_u16())==correct_csum); return OP_SUCCESS; } /* End of setSumRandom() */ /** Returns the TCP checksum field in NETWORK byte order */ u16 TCPHeader::getSum() const { return h.th_sum; } /* End of getSum() */ /* Copies the supplied buffer into the TCP options field. Note that the supplied * buffer MUST NOT exceed MAX_TCP_OPTIONS_LEN octets and should be a multiple of * four. If it is not a multiple of four, no error will be returned but the * behaviour is unspecified. If this method is called passing NULL and zero * ( t.setOptions(NULL, 0), any existing options are cleared, and the object's * internal length is updated accordingly. Also, note that a call to setOptions() * involves an automatic call to setOffset(), which updates the Offset field * to take into account the new header length. If you need to set a bogus * data offset, you can do so after calling setOptions(), but not before. * It returns OP_SUCCESS on success and OP_FAILURE in case of error */ int TCPHeader::setOptions(const u8 *optsbuff, size_t optslen){ /* NULL and length=0 means delete existing options */ if(optsbuff==NULL && optslen==0){ this->tcpoptlen=0; this->length=TCP_HEADER_LEN; memset(this->h.options, 0, MAX_TCP_OPTIONS_LEN); return OP_SUCCESS; /* Make sure params are safe to use */ }else if(optsbuff==NULL || optslen==0 || optslen>MAX_TCP_OPTIONS_LEN){ return OP_FAILURE; /* Copy supplied buffer into the options field, and update the offset field. */ }else{ memcpy(this->h.options, optsbuff, optslen); this->tcpoptlen=optslen; this->length=TCP_HEADER_LEN+optslen; this->setOffset(); return OP_SUCCESS; } } /* End of setOptions() */ /* Returns a pointer to the start of the TCP options field. If the supplied * "optslen" pointer is not NULL, the length of the options will be stored * there. */ const u8 *TCPHeader::getOptions(size_t *optslen) const { if(optslen!=NULL) *optslen=this->tcpoptlen; return this->h.options; } /* End of getOptions() */ /* Returns the index-th option in the TCP header. On success it returns a * structure filled with option information. If there is no index-th option, * it returns a structure with st.value==NULL. Note that this function does * not perform strict validity checking. It does check that the length claimed * by the options does not exceed the available buffer but it does not check, * for example, that the MSS option always contains a length of 4. Also, * if the returned option type is TCPOPT_EOL or TCPOPT_NOOP, the len field * would be set to zero and the "value" field should NOT be accessed, as it * will not contain reliable information. */ nping_tcp_opt_t TCPHeader::getOption(unsigned int index) const { nping_tcp_opt_t *curr_opt=NULL; u8 *curr_pnt=(u8 *)this->h.options; int bytes_left=this->length - TCP_HEADER_LEN; assert((this->length - TCP_HEADER_LEN) == this->tcpoptlen); unsigned int optsfound=0; nping_tcp_opt_t result; memset(&result, 0, sizeof(nping_tcp_opt_t)); while(bytes_left>0){ /* Use the opts structure as a template to access current option. It is * OK to use it because we only access the first two elements. */ curr_opt=(nping_tcp_opt_t *)curr_pnt; /* If we are right in the option that the caller wants, just return it */ if(optsfound==index){ result.type=curr_opt->type; if(result.type==TCPOPT_EOL || result.type==TCPOPT_NOOP) result.len=1; else result.len=curr_opt->len; result.value=(u8 *)curr_pnt+2; return result; } /* Otherwise, we have to parse it, so we can skip it and access the next * option */ switch(curr_opt->type){ /* EOL or NOOP +-+-+-+-+-+-+-+-+ | X | +-+-+-+-+-+-+-+-+ */ case TCPOPT_EOL: case TCPOPT_NOOP: curr_pnt++; /* Skip one octet */ bytes_left--; break; /* TLV encoded option */ default: /* If we don't have as many octets as the option advertises, the * option is bogus. Return failure. */ if(bytes_leftlen) return result; curr_pnt+=curr_opt->len; bytes_left-=curr_opt->len; break; } optsfound++; } return result; } /* Returns a textual representation of a TCP Options code */ const char *TCPHeader::optcode2str(u8 optcode){ switch(optcode){ case TCPOPT_EOL: return "EOL"; case TCPOPT_NOOP: return "NOOP"; case TCPOPT_MSS: return "MSS"; case TCPOPT_WSCALE: return "WScale"; case TCPOPT_SACKOK: return "SAckOK"; case TCPOPT_SACK: return "SAck"; case TCPOPT_ECHOREQ: return "EchoReq"; case TCPOPT_ECHOREP: return "EchoRep"; case TCPOPT_TSTAMP: return "TStamp"; case TCPOPT_POCP: return "POCP"; case TCPOPT_POSP: return "POSP"; case TCPOPT_CC: return "CC"; case TCPOPT_CCNEW: return "CC.NEW"; case TCPOPT_CCECHO: return "CC.ECHO"; case TCPOPT_ALTCSUMREQ: return "AltSumReq"; case TCPOPT_ALTCSUMDATA: return "AltSumData"; case TCPOPT_MD5: return "MD5"; case TCPOPT_SCPS: return "SCPS"; case TCPOPT_SNACK: return "SNAck"; case TCPOPT_QSRES: return "QStart"; case TCPOPT_UTO: return "UTO"; case TCPOPT_AO: return "AO"; default: return "Unknown"; } } /* End of optcode2str() */