1147072Sbrooks/* $OpenBSD: bpf.c,v 1.13 2004/05/05 14:28:58 deraadt Exp $ */ 2147072Sbrooks 3147072Sbrooks/* BPF socket interface code, originally contributed by Archie Cobbs. */ 4147072Sbrooks 5147072Sbrooks/* 6147072Sbrooks * Copyright (c) 1995, 1996, 1998, 1999 7147072Sbrooks * The Internet Software Consortium. All rights reserved. 8147072Sbrooks * 9147072Sbrooks * Redistribution and use in source and binary forms, with or without 10147072Sbrooks * modification, are permitted provided that the following conditions 11147072Sbrooks * are met: 12147072Sbrooks * 13147072Sbrooks * 1. Redistributions of source code must retain the above copyright 14147072Sbrooks * notice, this list of conditions and the following disclaimer. 15147072Sbrooks * 2. Redistributions in binary form must reproduce the above copyright 16147072Sbrooks * notice, this list of conditions and the following disclaimer in the 17147072Sbrooks * documentation and/or other materials provided with the distribution. 18147072Sbrooks * 3. Neither the name of The Internet Software Consortium nor the names 19147072Sbrooks * of its contributors may be used to endorse or promote products derived 20147072Sbrooks * from this software without specific prior written permission. 21147072Sbrooks * 22147072Sbrooks * THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND 23147072Sbrooks * CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, 24147072Sbrooks * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 25147072Sbrooks * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 26147072Sbrooks * DISCLAIMED. IN NO EVENT SHALL THE INTERNET SOFTWARE CONSORTIUM OR 27147072Sbrooks * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 28147072Sbrooks * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 29147072Sbrooks * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF 30147072Sbrooks * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND 31147072Sbrooks * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 32147072Sbrooks * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 33147072Sbrooks * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34147072Sbrooks * SUCH DAMAGE. 35147072Sbrooks * 36147072Sbrooks * This software has been written for the Internet Software Consortium 37147072Sbrooks * by Ted Lemon <mellon@fugue.com> in cooperation with Vixie 38147072Sbrooks * Enterprises. To learn more about the Internet Software Consortium, 39147072Sbrooks * see ``http://www.vix.com/isc''. To learn more about Vixie 40147072Sbrooks * Enterprises, see ``http://www.vix.com''. 41147072Sbrooks */ 42147072Sbrooks 43149399Sbrooks#include <sys/cdefs.h> 44149399Sbrooks__FBSDID("$FreeBSD$"); 45149399Sbrooks 46147072Sbrooks#include "dhcpd.h" 47147072Sbrooks#include <sys/ioctl.h> 48147072Sbrooks#include <sys/uio.h> 49147072Sbrooks 50147072Sbrooks#include <net/bpf.h> 51147072Sbrooks#include <netinet/in_systm.h> 52147072Sbrooks#include <netinet/ip.h> 53147072Sbrooks#include <netinet/udp.h> 54147072Sbrooks#include <netinet/if_ether.h> 55147072Sbrooks 56147072Sbrooks#define BPF_FORMAT "/dev/bpf%d" 57147072Sbrooks 58147072Sbrooks/* 59147072Sbrooks * Called by get_interface_list for each interface that's discovered. 60147072Sbrooks * Opens a packet filter for each interface and adds it to the select 61147072Sbrooks * mask. 62147072Sbrooks */ 63147072Sbrooksint 64147072Sbrooksif_register_bpf(struct interface_info *info) 65147072Sbrooks{ 66147072Sbrooks char filename[50]; 67147072Sbrooks int sock, b; 68147072Sbrooks 69147072Sbrooks /* Open a BPF device */ 70147072Sbrooks for (b = 0; 1; b++) { 71147072Sbrooks snprintf(filename, sizeof(filename), BPF_FORMAT, b); 72147072Sbrooks sock = open(filename, O_RDWR, 0); 73147072Sbrooks if (sock < 0) { 74147072Sbrooks if (errno == EBUSY) 75147072Sbrooks continue; 76147072Sbrooks else 77147072Sbrooks error("Can't find free bpf: %m"); 78147072Sbrooks } else 79147072Sbrooks break; 80147072Sbrooks } 81147072Sbrooks 82147072Sbrooks /* Set the BPF device to point at this interface. */ 83147072Sbrooks if (ioctl(sock, BIOCSETIF, info->ifp) < 0) 84147072Sbrooks error("Can't attach interface %s to bpf device %s: %m", 85147072Sbrooks info->name, filename); 86147072Sbrooks 87147072Sbrooks return (sock); 88147072Sbrooks} 89147072Sbrooks 90147072Sbrooksvoid 91147072Sbrooksif_register_send(struct interface_info *info) 92147072Sbrooks{ 93198352Sphilip int sock, on = 1; 94198352Sphilip 95147072Sbrooks /* 96147072Sbrooks * If we're using the bpf API for sending and receiving, we 97147072Sbrooks * don't need to register this interface twice. 98147072Sbrooks */ 99147072Sbrooks info->wfdesc = info->rfdesc; 100198352Sphilip 101198352Sphilip /* 102198352Sphilip * Use raw socket for unicast send. 103198352Sphilip */ 104198352Sphilip if ((sock = socket(AF_INET, SOCK_RAW, IPPROTO_UDP)) == -1) 105198352Sphilip error("socket(SOCK_RAW): %m"); 106198352Sphilip if (setsockopt(sock, IPPROTO_IP, IP_HDRINCL, &on, 107198352Sphilip sizeof(on)) == -1) 108198352Sphilip error("setsockopt(IP_HDRINCL): %m"); 109198352Sphilip info->ufdesc = sock; 110147072Sbrooks} 111147072Sbrooks 112147072Sbrooks/* 113147072Sbrooks * Packet filter program... 114147072Sbrooks * 115147072Sbrooks * XXX: Changes to the filter program may require changes to the 116147072Sbrooks * constant offsets used in if_register_send to patch the BPF program! 117147072Sbrooks */ 118147072Sbrooksstruct bpf_insn dhcp_bpf_filter[] = { 119147072Sbrooks /* Make sure this is an IP packet... */ 120147072Sbrooks BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 12), 121147072Sbrooks BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 8), 122147072Sbrooks 123147072Sbrooks /* Make sure it's a UDP packet... */ 124147072Sbrooks BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 23), 125147072Sbrooks BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 6), 126147072Sbrooks 127147072Sbrooks /* Make sure this isn't a fragment... */ 128147072Sbrooks BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20), 129147072Sbrooks BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 4, 0), 130147072Sbrooks 131147072Sbrooks /* Get the IP header length... */ 132147072Sbrooks BPF_STMT(BPF_LDX + BPF_B + BPF_MSH, 14), 133147072Sbrooks 134147072Sbrooks /* Make sure it's to the right port... */ 135147072Sbrooks BPF_STMT(BPF_LD + BPF_H + BPF_IND, 16), 136147072Sbrooks BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 67, 0, 1), /* patch */ 137147072Sbrooks 138147072Sbrooks /* If we passed all the tests, ask for the whole packet. */ 139147072Sbrooks BPF_STMT(BPF_RET+BPF_K, (u_int)-1), 140147072Sbrooks 141147072Sbrooks /* Otherwise, drop it. */ 142147072Sbrooks BPF_STMT(BPF_RET+BPF_K, 0), 143147072Sbrooks}; 144147072Sbrooks 145147072Sbrooksint dhcp_bpf_filter_len = sizeof(dhcp_bpf_filter) / sizeof(struct bpf_insn); 146147072Sbrooks 147147072Sbrooks/* 148147072Sbrooks * Packet write filter program: 149147072Sbrooks * 'ip and udp and src port bootps and dst port (bootps or bootpc)' 150147072Sbrooks */ 151147072Sbrooksstruct bpf_insn dhcp_bpf_wfilter[] = { 152147072Sbrooks BPF_STMT(BPF_LD + BPF_B + BPF_IND, 14), 153147072Sbrooks BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, (IPVERSION << 4) + 5, 0, 12), 154147072Sbrooks 155147072Sbrooks /* Make sure this is an IP packet... */ 156147072Sbrooks BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 12), 157147072Sbrooks BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 10), 158147072Sbrooks 159147072Sbrooks /* Make sure it's a UDP packet... */ 160147072Sbrooks BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 23), 161147072Sbrooks BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 8), 162147072Sbrooks 163147072Sbrooks /* Make sure this isn't a fragment... */ 164147072Sbrooks BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20), 165147072Sbrooks BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 6, 0), /* patched */ 166147072Sbrooks 167147072Sbrooks /* Get the IP header length... */ 168147072Sbrooks BPF_STMT(BPF_LDX + BPF_B + BPF_MSH, 14), 169147072Sbrooks 170147072Sbrooks /* Make sure it's from the right port... */ 171147072Sbrooks BPF_STMT(BPF_LD + BPF_H + BPF_IND, 14), 172147072Sbrooks BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 68, 0, 3), 173147072Sbrooks 174147072Sbrooks /* Make sure it is to the right ports ... */ 175147072Sbrooks BPF_STMT(BPF_LD + BPF_H + BPF_IND, 16), 176147072Sbrooks BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 67, 0, 1), 177147072Sbrooks 178147072Sbrooks /* If we passed all the tests, ask for the whole packet. */ 179147072Sbrooks BPF_STMT(BPF_RET+BPF_K, (u_int)-1), 180147072Sbrooks 181147072Sbrooks /* Otherwise, drop it. */ 182147072Sbrooks BPF_STMT(BPF_RET+BPF_K, 0), 183147072Sbrooks}; 184147072Sbrooks 185147072Sbrooksint dhcp_bpf_wfilter_len = sizeof(dhcp_bpf_wfilter) / sizeof(struct bpf_insn); 186147072Sbrooks 187147072Sbrooksvoid 188147072Sbrooksif_register_receive(struct interface_info *info) 189147072Sbrooks{ 190147072Sbrooks struct bpf_version v; 191147072Sbrooks struct bpf_program p; 192147072Sbrooks int flag = 1, sz; 193147072Sbrooks 194147072Sbrooks /* Open a BPF device and hang it on this interface... */ 195147072Sbrooks info->rfdesc = if_register_bpf(info); 196147072Sbrooks 197147072Sbrooks /* Make sure the BPF version is in range... */ 198147072Sbrooks if (ioctl(info->rfdesc, BIOCVERSION, &v) < 0) 199147072Sbrooks error("Can't get BPF version: %m"); 200147072Sbrooks 201147072Sbrooks if (v.bv_major != BPF_MAJOR_VERSION || 202147072Sbrooks v.bv_minor < BPF_MINOR_VERSION) 203147072Sbrooks error("Kernel BPF version out of range - recompile dhcpd!"); 204147072Sbrooks 205147072Sbrooks /* 206147072Sbrooks * Set immediate mode so that reads return as soon as a packet 207147072Sbrooks * comes in, rather than waiting for the input buffer to fill 208147072Sbrooks * with packets. 209147072Sbrooks */ 210147072Sbrooks if (ioctl(info->rfdesc, BIOCIMMEDIATE, &flag) < 0) 211147072Sbrooks error("Can't set immediate mode on bpf device: %m"); 212147072Sbrooks 213147072Sbrooks /* Get the required BPF buffer length from the kernel. */ 214147072Sbrooks if (ioctl(info->rfdesc, BIOCGBLEN, &sz) < 0) 215147072Sbrooks error("Can't get bpf buffer length: %m"); 216147072Sbrooks info->rbuf_max = sz; 217147072Sbrooks info->rbuf = malloc(info->rbuf_max); 218147072Sbrooks if (!info->rbuf) 219147072Sbrooks error("Can't allocate %lu bytes for bpf input buffer.", 220147072Sbrooks (unsigned long)info->rbuf_max); 221147072Sbrooks info->rbuf_offset = 0; 222147072Sbrooks info->rbuf_len = 0; 223147072Sbrooks 224147072Sbrooks /* Set up the bpf filter program structure. */ 225147072Sbrooks p.bf_len = dhcp_bpf_filter_len; 226147072Sbrooks p.bf_insns = dhcp_bpf_filter; 227147072Sbrooks 228147072Sbrooks /* Patch the server port into the BPF program... 229147072Sbrooks * 230147072Sbrooks * XXX: changes to filter program may require changes to the 231147072Sbrooks * insn number(s) used below! 232147072Sbrooks */ 233147072Sbrooks dhcp_bpf_filter[8].k = LOCAL_PORT; 234147072Sbrooks 235147072Sbrooks if (ioctl(info->rfdesc, BIOCSETF, &p) < 0) 236147072Sbrooks error("Can't install packet filter program: %m"); 237147072Sbrooks 238147072Sbrooks /* Set up the bpf write filter program structure. */ 239147072Sbrooks p.bf_len = dhcp_bpf_wfilter_len; 240147072Sbrooks p.bf_insns = dhcp_bpf_wfilter; 241147072Sbrooks 242147072Sbrooks if (dhcp_bpf_wfilter[7].k == 0x1fff) 243147072Sbrooks dhcp_bpf_wfilter[7].k = htons(IP_MF|IP_OFFMASK); 244147072Sbrooks 245147072Sbrooks if (ioctl(info->rfdesc, BIOCSETWF, &p) < 0) 246147072Sbrooks error("Can't install write filter program: %m"); 247147072Sbrooks 248147072Sbrooks if (ioctl(info->rfdesc, BIOCLOCK, NULL) < 0) 249147072Sbrooks error("Cannot lock bpf"); 250147072Sbrooks} 251147072Sbrooks 252147072Sbrooksssize_t 253147072Sbrookssend_packet(struct interface_info *interface, struct dhcp_packet *raw, 254147072Sbrooks size_t len, struct in_addr from, struct sockaddr_in *to, 255147072Sbrooks struct hardware *hto) 256147072Sbrooks{ 257147072Sbrooks unsigned char buf[256]; 258147072Sbrooks struct iovec iov[2]; 259198352Sphilip struct msghdr msg; 260147072Sbrooks int result, bufp = 0; 261147072Sbrooks 262147072Sbrooks /* Assemble the headers... */ 263198352Sphilip if (to->sin_addr.s_addr == INADDR_BROADCAST) 264198352Sphilip assemble_hw_header(interface, buf, &bufp, hto); 265147072Sbrooks assemble_udp_ip_header(buf, &bufp, from.s_addr, 266147072Sbrooks to->sin_addr.s_addr, to->sin_port, (unsigned char *)raw, len); 267147072Sbrooks 268147072Sbrooks iov[0].iov_base = (char *)buf; 269147072Sbrooks iov[0].iov_len = bufp; 270147072Sbrooks iov[1].iov_base = (char *)raw; 271147072Sbrooks iov[1].iov_len = len; 272147072Sbrooks 273198352Sphilip /* Fire it off */ 274198352Sphilip if (to->sin_addr.s_addr == INADDR_BROADCAST) 275198352Sphilip result = writev(interface->wfdesc, iov, 2); 276198352Sphilip else { 277198352Sphilip memset(&msg, 0, sizeof(msg)); 278198352Sphilip msg.msg_name = (struct sockaddr *)to; 279198352Sphilip msg.msg_namelen = sizeof(*to); 280198352Sphilip msg.msg_iov = iov; 281198352Sphilip msg.msg_iovlen = 2; 282198352Sphilip result = sendmsg(interface->ufdesc, &msg, 0); 283198352Sphilip } 284198352Sphilip 285147072Sbrooks if (result < 0) 286147072Sbrooks warning("send_packet: %m"); 287147072Sbrooks return (result); 288147072Sbrooks} 289147072Sbrooks 290147072Sbrooksssize_t 291147072Sbrooksreceive_packet(struct interface_info *interface, unsigned char *buf, 292147072Sbrooks size_t len, struct sockaddr_in *from, struct hardware *hfrom) 293147072Sbrooks{ 294147072Sbrooks int length = 0, offset = 0; 295147072Sbrooks struct bpf_hdr hdr; 296147072Sbrooks 297147072Sbrooks /* 298147072Sbrooks * All this complexity is because BPF doesn't guarantee that 299147072Sbrooks * only one packet will be returned at a time. We're getting 300147072Sbrooks * what we deserve, though - this is a terrible abuse of the BPF 301147072Sbrooks * interface. Sigh. 302147072Sbrooks */ 303147072Sbrooks 304147072Sbrooks /* Process packets until we get one we can return or until we've 305147072Sbrooks * done a read and gotten nothing we can return... 306147072Sbrooks */ 307147072Sbrooks do { 308147072Sbrooks /* If the buffer is empty, fill it. */ 309162641Sbrooks if (interface->rbuf_offset >= interface->rbuf_len) { 310147072Sbrooks length = read(interface->rfdesc, interface->rbuf, 311147072Sbrooks interface->rbuf_max); 312147072Sbrooks if (length <= 0) 313147072Sbrooks return (length); 314147072Sbrooks interface->rbuf_offset = 0; 315147072Sbrooks interface->rbuf_len = length; 316147072Sbrooks } 317147072Sbrooks 318147072Sbrooks /* 319147072Sbrooks * If there isn't room for a whole bpf header, something 320147072Sbrooks * went wrong, but we'll ignore it and hope it goes 321147072Sbrooks * away... XXX 322147072Sbrooks */ 323147072Sbrooks if (interface->rbuf_len - interface->rbuf_offset < 324147072Sbrooks sizeof(hdr)) { 325147072Sbrooks interface->rbuf_offset = interface->rbuf_len; 326147072Sbrooks continue; 327147072Sbrooks } 328147072Sbrooks 329147072Sbrooks /* Copy out a bpf header... */ 330147072Sbrooks memcpy(&hdr, &interface->rbuf[interface->rbuf_offset], 331147072Sbrooks sizeof(hdr)); 332147072Sbrooks 333147072Sbrooks /* 334147072Sbrooks * If the bpf header plus data doesn't fit in what's 335147072Sbrooks * left of the buffer, stick head in sand yet again... 336147072Sbrooks */ 337147072Sbrooks if (interface->rbuf_offset + hdr.bh_hdrlen + hdr.bh_caplen > 338147072Sbrooks interface->rbuf_len) { 339147072Sbrooks interface->rbuf_offset = interface->rbuf_len; 340147072Sbrooks continue; 341147072Sbrooks } 342147072Sbrooks 343148451Sbrooks /* Skip over the BPF header... */ 344148451Sbrooks interface->rbuf_offset += hdr.bh_hdrlen; 345148451Sbrooks 346147072Sbrooks /* 347147072Sbrooks * If the captured data wasn't the whole packet, or if 348147072Sbrooks * the packet won't fit in the input buffer, all we can 349147072Sbrooks * do is drop it. 350147072Sbrooks */ 351147072Sbrooks if (hdr.bh_caplen != hdr.bh_datalen) { 352148484Sbrooks interface->rbuf_offset = 353148484Sbrooks BPF_WORDALIGN(interface->rbuf_offset + 354148484Sbrooks hdr.bh_caplen); 355147072Sbrooks continue; 356147072Sbrooks } 357147072Sbrooks 358147072Sbrooks /* Decode the physical header... */ 359147072Sbrooks offset = decode_hw_header(interface->rbuf, 360147072Sbrooks interface->rbuf_offset, hfrom); 361147072Sbrooks 362147072Sbrooks /* 363147072Sbrooks * If a physical layer checksum failed (dunno of any 364147072Sbrooks * physical layer that supports this, but WTH), skip 365147072Sbrooks * this packet. 366147072Sbrooks */ 367147072Sbrooks if (offset < 0) { 368148484Sbrooks interface->rbuf_offset = 369148484Sbrooks BPF_WORDALIGN(interface->rbuf_offset + 370148484Sbrooks hdr.bh_caplen); 371147072Sbrooks continue; 372147072Sbrooks } 373147072Sbrooks interface->rbuf_offset += offset; 374147072Sbrooks hdr.bh_caplen -= offset; 375147072Sbrooks 376147072Sbrooks /* Decode the IP and UDP headers... */ 377147072Sbrooks offset = decode_udp_ip_header(interface->rbuf, 378147072Sbrooks interface->rbuf_offset, from, NULL, hdr.bh_caplen); 379147072Sbrooks 380147072Sbrooks /* If the IP or UDP checksum was bad, skip the packet... */ 381147072Sbrooks if (offset < 0) { 382148484Sbrooks interface->rbuf_offset = 383148484Sbrooks BPF_WORDALIGN(interface->rbuf_offset + 384148484Sbrooks hdr.bh_caplen); 385147072Sbrooks continue; 386147072Sbrooks } 387147072Sbrooks interface->rbuf_offset += offset; 388147072Sbrooks hdr.bh_caplen -= offset; 389147072Sbrooks 390147072Sbrooks /* 391147072Sbrooks * If there's not enough room to stash the packet data, 392147072Sbrooks * we have to skip it (this shouldn't happen in real 393147072Sbrooks * life, though). 394147072Sbrooks */ 395147072Sbrooks if (hdr.bh_caplen > len) { 396148484Sbrooks interface->rbuf_offset = 397148484Sbrooks BPF_WORDALIGN(interface->rbuf_offset + 398148484Sbrooks hdr.bh_caplen); 399147072Sbrooks continue; 400147072Sbrooks } 401147072Sbrooks 402147072Sbrooks /* Copy out the data in the packet... */ 403147072Sbrooks memcpy(buf, interface->rbuf + interface->rbuf_offset, 404147072Sbrooks hdr.bh_caplen); 405148484Sbrooks interface->rbuf_offset = 406148484Sbrooks BPF_WORDALIGN(interface->rbuf_offset + 407148484Sbrooks hdr.bh_caplen); 408147072Sbrooks return (hdr.bh_caplen); 409147072Sbrooks } while (!length); 410147072Sbrooks return (0); 411147072Sbrooks} 412