bpf.c revision 252620
1193326Sed/* $OpenBSD: bpf.c,v 1.13 2004/05/05 14:28:58 deraadt Exp $ */ 2193326Sed 3193326Sed/* BPF socket interface code, originally contributed by Archie Cobbs. */ 4193326Sed 5193326Sed/* 6193326Sed * Copyright (c) 1995, 1996, 1998, 1999 7193326Sed * The Internet Software Consortium. All rights reserved. 8193326Sed * 9193326Sed * Redistribution and use in source and binary forms, with or without 10193326Sed * modification, are permitted provided that the following conditions 11193326Sed * are met: 12193326Sed * 13193326Sed * 1. Redistributions of source code must retain the above copyright 14212904Sdim * notice, this list of conditions and the following disclaimer. 15221345Sdim * 2. Redistributions in binary form must reproduce the above copyright 16193326Sed * notice, this list of conditions and the following disclaimer in the 17193326Sed * documentation and/or other materials provided with the distribution. 18263508Sdim * 3. Neither the name of The Internet Software Consortium nor the names 19198092Srdivacky * of its contributors may be used to endorse or promote products derived 20249423Sdim * from this software without specific prior written permission. 21239462Sdim * 22212904Sdim * THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND 23212904Sdim * CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, 24193326Sed * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 25221345Sdim * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 26193326Sed * DISCLAIMED. IN NO EVENT SHALL THE INTERNET SOFTWARE CONSORTIUM OR 27193326Sed * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 28198092Srdivacky * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 29198092Srdivacky * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF 30193326Sed * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND 31249423Sdim * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 32249423Sdim * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 33249423Sdim * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34249423Sdim * SUCH DAMAGE. 35249423Sdim * 36249423Sdim * This software has been written for the Internet Software Consortium 37249423Sdim * by Ted Lemon <mellon@fugue.com> in cooperation with Vixie 38249423Sdim * Enterprises. To learn more about the Internet Software Consortium, 39249423Sdim * see ``http://www.vix.com/isc''. To learn more about Vixie 40249423Sdim * Enterprises, see ``http://www.vix.com''. 41249423Sdim */ 42249423Sdim 43263508Sdim#include <sys/cdefs.h> 44234353Sdim__FBSDID("$FreeBSD: head/sbin/dhclient/bpf.c 252620 2013-07-03 22:01:52Z pjd $"); 45201361Srdivacky 46193326Sed#include "dhcpd.h" 47198092Srdivacky#include <sys/ioctl.h> 48193326Sed#include <sys/uio.h> 49193326Sed 50212904Sdim#include <net/bpf.h> 51193326Sed#include <netinet/in_systm.h> 52224145Sdim#include <netinet/ip.h> 53224145Sdim#include <netinet/udp.h> 54224145Sdim#include <netinet/if_ether.h> 55224145Sdim 56224145Sdim#define BPF_FORMAT "/dev/bpf%d" 57224145Sdim 58212904Sdim/* 59193326Sed * Called by get_interface_list for each interface that's discovered. 60193326Sed * Opens a packet filter for each interface and adds it to the select 61234353Sdim * mask. 62234353Sdim */ 63234353Sdimint 64234353Sdimif_register_bpf(struct interface_info *info, int flags) 65239462Sdim{ 66239462Sdim char filename[50]; 67234353Sdim int sock, b; 68234353Sdim 69234353Sdim /* Open a BPF device */ 70234353Sdim for (b = 0;; b++) { 71234353Sdim snprintf(filename, sizeof(filename), BPF_FORMAT, b); 72234353Sdim sock = open(filename, flags); 73234353Sdim if (sock < 0) { 74234353Sdim if (errno == EBUSY) 75234353Sdim continue; 76234353Sdim else 77239462Sdim error("Can't find free bpf: %m"); 78234353Sdim } else 79234353Sdim break; 80234353Sdim } 81234353Sdim 82239462Sdim /* Set the BPF device to point at this interface. */ 83234353Sdim if (ioctl(sock, BIOCSETIF, info->ifp) < 0) 84234353Sdim error("Can't attach interface %s to bpf device %s: %m", 85234353Sdim info->name, filename); 86234353Sdim 87239462Sdim return (sock); 88239462Sdim} 89239462Sdim 90239462Sdim/* 91239462Sdim * Packet write filter program: 92239462Sdim * 'ip and udp and src port bootps and dst port (bootps or bootpc)' 93239462Sdim */ 94239462Sdimstruct bpf_insn dhcp_bpf_wfilter[] = { 95239462Sdim BPF_STMT(BPF_LD + BPF_B + BPF_IND, 14), 96239462Sdim BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, (IPVERSION << 4) + 5, 0, 12), 97239462Sdim 98239462Sdim /* Make sure this is an IP packet... */ 99239462Sdim BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 12), 100239462Sdim BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 10), 101239462Sdim 102239462Sdim /* Make sure it's a UDP packet... */ 103239462Sdim BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 23), 104239462Sdim BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 8), 105239462Sdim 106239462Sdim /* Make sure this isn't a fragment... */ 107239462Sdim BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20), 108239462Sdim BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 6, 0), /* patched */ 109239462Sdim 110239462Sdim /* Get the IP header length... */ 111239462Sdim BPF_STMT(BPF_LDX + BPF_B + BPF_MSH, 14), 112239462Sdim 113263508Sdim /* Make sure it's from the right port... */ 114239462Sdim BPF_STMT(BPF_LD + BPF_H + BPF_IND, 14), 115239462Sdim BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 68, 0, 3), 116239462Sdim 117239462Sdim /* Make sure it is to the right ports ... */ 118239462Sdim BPF_STMT(BPF_LD + BPF_H + BPF_IND, 16), 119239462Sdim BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 67, 0, 1), 120239462Sdim 121239462Sdim /* If we passed all the tests, ask for the whole packet. */ 122239462Sdim BPF_STMT(BPF_RET+BPF_K, (u_int)-1), 123239462Sdim 124193326Sed /* Otherwise, drop it. */ 125193326Sed BPF_STMT(BPF_RET+BPF_K, 0), 126193326Sed}; 127193326Sed 128193326Sedint dhcp_bpf_wfilter_len = sizeof(dhcp_bpf_wfilter) / sizeof(struct bpf_insn); 129193326Sed 130193326Sedvoid 131193326Sedif_register_send(struct interface_info *info) 132251662Sdim{ 133212904Sdim struct bpf_version v; 134218893Sdim struct bpf_program p; 135221345Sdim int sock, on = 1; 136234353Sdim 137226633Sdim /* Open a BPF device and hang it on this interface... */ 138226633Sdim info->wfdesc = if_register_bpf(info, O_WRONLY); 139199990Srdivacky 140199990Srdivacky /* Make sure the BPF version is in range... */ 141199990Srdivacky if (ioctl(info->wfdesc, BIOCVERSION, &v) < 0) 142212904Sdim error("Can't get BPF version: %m"); 143199990Srdivacky 144199990Srdivacky if (v.bv_major != BPF_MAJOR_VERSION || 145207619Srdivacky v.bv_minor < BPF_MINOR_VERSION) 146199990Srdivacky error("Kernel BPF version out of range - recompile dhcpd!"); 147199990Srdivacky 148199990Srdivacky /* Set up the bpf write filter program structure. */ 149199990Srdivacky p.bf_len = dhcp_bpf_wfilter_len; 150199990Srdivacky p.bf_insns = dhcp_bpf_wfilter; 151199990Srdivacky 152199990Srdivacky if (dhcp_bpf_wfilter[7].k == 0x1fff) 153199990Srdivacky dhcp_bpf_wfilter[7].k = htons(IP_MF|IP_OFFMASK); 154199990Srdivacky 155199990Srdivacky if (ioctl(info->wfdesc, BIOCSETWF, &p) < 0) 156199990Srdivacky error("Can't install write filter program: %m"); 157199990Srdivacky 158199990Srdivacky if (ioctl(info->wfdesc, BIOCLOCK, NULL) < 0) 159234353Sdim error("Cannot lock bpf"); 160212904Sdim 161199990Srdivacky /* 162210299Sed * Use raw socket for unicast send. 163210299Sed */ 164221345Sdim if ((sock = socket(AF_INET, SOCK_RAW, IPPROTO_UDP)) == -1) 165221345Sdim error("socket(SOCK_RAW): %m"); 166221345Sdim if (setsockopt(sock, IPPROTO_IP, IP_HDRINCL, &on, 167221345Sdim sizeof(on)) == -1) 168212904Sdim error("setsockopt(IP_HDRINCL): %m"); 169221345Sdim info->ufdesc = sock; 170221345Sdim} 171221345Sdim 172221345Sdim/* 173199990Srdivacky * Packet filter program... 174199990Srdivacky * 175212904Sdim * XXX: Changes to the filter program may require changes to the 176199990Srdivacky * constant offsets used in if_register_send to patch the BPF program! 177199990Srdivacky */ 178207619Srdivackystruct bpf_insn dhcp_bpf_filter[] = { 179207619Srdivacky /* Make sure this is an IP packet... */ 180212904Sdim BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 12), 181198092Srdivacky BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 8), 182201361Srdivacky 183201361Srdivacky /* Make sure it's a UDP packet... */ 184201361Srdivacky BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 23), 185201361Srdivacky BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 6), 186201361Srdivacky 187201361Srdivacky /* Make sure this isn't a fragment... */ 188199990Srdivacky BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20), 189199990Srdivacky BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 4, 0), 190199990Srdivacky 191199990Srdivacky /* Get the IP header length... */ 192199990Srdivacky BPF_STMT(BPF_LDX + BPF_B + BPF_MSH, 14), 193199990Srdivacky 194198092Srdivacky /* Make sure it's to the right port... */ 195199990Srdivacky BPF_STMT(BPF_LD + BPF_H + BPF_IND, 16), 196199990Srdivacky BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 67, 0, 1), /* patch */ 197199990Srdivacky 198199990Srdivacky /* If we passed all the tests, ask for the whole packet. */ 199199990Srdivacky BPF_STMT(BPF_RET+BPF_K, (u_int)-1), 200199990Srdivacky 201199990Srdivacky /* Otherwise, drop it. */ 202199990Srdivacky BPF_STMT(BPF_RET+BPF_K, 0), 203199990Srdivacky}; 204199990Srdivacky 205199990Srdivackyint dhcp_bpf_filter_len = sizeof(dhcp_bpf_filter) / sizeof(struct bpf_insn); 206199990Srdivacky 207199990Srdivackyvoid 208199990Srdivackyif_register_receive(struct interface_info *info) 209193326Sed{ 210199482Srdivacky struct bpf_version v; 211193326Sed struct bpf_program p; 212202379Srdivacky int flag = 1, sz; 213226633Sdim 214239462Sdim /* Open a BPF device and hang it on this interface... */ 215226633Sdim info->rfdesc = if_register_bpf(info, O_RDONLY); 216234353Sdim 217226633Sdim /* Make sure the BPF version is in range... */ 218226633Sdim if (ioctl(info->rfdesc, BIOCVERSION, &v) < 0) 219226633Sdim error("Can't get BPF version: %m"); 220226633Sdim 221226633Sdim if (v.bv_major != BPF_MAJOR_VERSION || 222226633Sdim v.bv_minor < BPF_MINOR_VERSION) 223226633Sdim error("Kernel BPF version out of range - recompile dhcpd!"); 224226633Sdim 225226633Sdim /* 226226633Sdim * Set immediate mode so that reads return as soon as a packet 227226633Sdim * comes in, rather than waiting for the input buffer to fill 228226633Sdim * with packets. 229226633Sdim */ 230226633Sdim if (ioctl(info->rfdesc, BIOCIMMEDIATE, &flag) < 0) 231226633Sdim error("Can't set immediate mode on bpf device: %m"); 232234353Sdim 233226633Sdim /* Get the required BPF buffer length from the kernel. */ 234226633Sdim if (ioctl(info->rfdesc, BIOCGBLEN, &sz) < 0) 235226633Sdim error("Can't get bpf buffer length: %m"); 236226633Sdim info->rbuf_max = sz; 237234353Sdim info->rbuf = malloc(info->rbuf_max); 238226633Sdim if (!info->rbuf) 239226633Sdim error("Can't allocate %lu bytes for bpf input buffer.", 240263508Sdim (unsigned long)info->rbuf_max); 241263508Sdim info->rbuf_offset = 0; 242263508Sdim info->rbuf_len = 0; 243226633Sdim 244226633Sdim /* Set up the bpf filter program structure. */ 245226633Sdim p.bf_len = dhcp_bpf_filter_len; 246226633Sdim p.bf_insns = dhcp_bpf_filter; 247226633Sdim 248226633Sdim /* Patch the server port into the BPF program... 249226633Sdim * 250226633Sdim * XXX: changes to filter program may require changes to the 251193326Sed * insn number(s) used below! 252199482Srdivacky */ 253203955Srdivacky dhcp_bpf_filter[8].k = LOCAL_PORT; 254212904Sdim 255193326Sed if (ioctl(info->rfdesc, BIOCSETF, &p) < 0) 256198893Srdivacky error("Can't install packet filter program: %m"); 257198092Srdivacky 258198092Srdivacky if (ioctl(info->rfdesc, BIOCLOCK, NULL) < 0) 259198092Srdivacky error("Cannot lock bpf"); 260198092Srdivacky} 261198092Srdivacky 262199482Srdivackyvoid 263199482Srdivackysend_packet(struct interface_info *interface, struct dhcp_packet *raw, 264212904Sdim size_t len, struct in_addr from, struct in_addr to) 265199482Srdivacky{ 266198092Srdivacky unsigned char buf[256]; 267193326Sed struct iovec iov[2]; 268193326Sed struct msghdr msg; 269193326Sed int result, bufp = 0; 270193326Sed 271198092Srdivacky /* Assemble the headers... */ 272198092Srdivacky if (to.s_addr == INADDR_BROADCAST) 273193326Sed assemble_hw_header(interface, buf, &bufp); 274193326Sed assemble_udp_ip_header(buf, &bufp, from.s_addr, to.s_addr, 275193326Sed htons(REMOTE_PORT), (unsigned char *)raw, len); 276193326Sed 277193326Sed iov[0].iov_base = buf; 278193326Sed iov[0].iov_len = bufp; 279193326Sed iov[1].iov_base = raw; 280193326Sed iov[1].iov_len = len; 281193326Sed 282193326Sed /* Fire it off */ 283193326Sed if (to.s_addr == INADDR_BROADCAST) 284193326Sed result = writev(interface->wfdesc, iov, 2); 285199482Srdivacky else { 286212904Sdim struct sockaddr_in sato; 287193326Sed 288193326Sed sato.sin_addr = to; 289193326Sed sato.sin_port = htons(REMOTE_PORT); 290193326Sed sato.sin_family = AF_INET; 291193326Sed sato.sin_len = sizeof(sato); 292193326Sed 293193326Sed memset(&msg, 0, sizeof(msg)); 294193326Sed msg.msg_name = (struct sockaddr *)&sato; 295193326Sed msg.msg_namelen = sizeof(sato); 296198092Srdivacky msg.msg_iov = iov; 297193326Sed msg.msg_iovlen = 2; 298193326Sed result = sendmsg(interface->ufdesc, &msg, 0); 299193326Sed } 300198893Srdivacky 301198092Srdivacky if (result < 0) 302198893Srdivacky warning("send_packet: %m"); 303198893Srdivacky} 304198893Srdivacky 305199482Srdivackyssize_t 306198893Srdivackyreceive_packet(struct interface_info *interface, unsigned char *buf, 307198893Srdivacky size_t len, struct sockaddr_in *from, struct hardware *hfrom) 308234353Sdim{ 309234353Sdim int length = 0, offset = 0; 310234353Sdim struct bpf_hdr hdr; 311234353Sdim 312234353Sdim /* 313221345Sdim * All this complexity is because BPF doesn't guarantee that 314221345Sdim * only one packet will be returned at a time. We're getting 315221345Sdim * what we deserve, though - this is a terrible abuse of the BPF 316221345Sdim * interface. Sigh. 317221345Sdim */ 318221345Sdim 319221345Sdim /* Process packets until we get one we can return or until we've 320234353Sdim * done a read and gotten nothing we can return... 321221345Sdim */ 322221345Sdim do { 323221345Sdim /* If the buffer is empty, fill it. */ 324221345Sdim if (interface->rbuf_offset >= interface->rbuf_len) { 325221345Sdim length = read(interface->rfdesc, interface->rbuf, 326221345Sdim interface->rbuf_max); 327198893Srdivacky if (length <= 0) 328221345Sdim return (length); 329218893Sdim interface->rbuf_offset = 0; 330218893Sdim interface->rbuf_len = length; 331218893Sdim } 332218893Sdim 333218893Sdim /* 334199482Srdivacky * If there isn't room for a whole bpf header, something 335199482Srdivacky * went wrong, but we'll ignore it and hope it goes 336212904Sdim * away... XXX 337199482Srdivacky */ 338212904Sdim if (interface->rbuf_len - interface->rbuf_offset < 339193326Sed sizeof(hdr)) { 340193326Sed interface->rbuf_offset = interface->rbuf_len; 341193326Sed continue; 342193326Sed } 343193326Sed 344243830Sdim /* Copy out a bpf header... */ 345243830Sdim memcpy(&hdr, &interface->rbuf[interface->rbuf_offset], 346193326Sed sizeof(hdr)); 347193326Sed 348199482Srdivacky /* 349199482Srdivacky * If the bpf header plus data doesn't fit in what's 350199482Srdivacky * left of the buffer, stick head in sand yet again... 351199482Srdivacky */ 352200583Srdivacky if (interface->rbuf_offset + hdr.bh_hdrlen + hdr.bh_caplen > 353193326Sed interface->rbuf_len) { 354208600Srdivacky interface->rbuf_offset = interface->rbuf_len; 355243830Sdim continue; 356208600Srdivacky } 357208600Srdivacky 358208600Srdivacky /* Skip over the BPF header... */ 359193326Sed interface->rbuf_offset += hdr.bh_hdrlen; 360193326Sed 361198092Srdivacky /* 362193326Sed * If the captured data wasn't the whole packet, or if 363193326Sed * the packet won't fit in the input buffer, all we can 364193326Sed * do is drop it. 365221345Sdim */ 366221345Sdim if (hdr.bh_caplen != hdr.bh_datalen) { 367221345Sdim interface->rbuf_offset = 368221345Sdim BPF_WORDALIGN(interface->rbuf_offset + 369221345Sdim hdr.bh_caplen); 370221345Sdim continue; 371221345Sdim } 372221345Sdim 373221345Sdim /* Decode the physical header... */ 374221345Sdim offset = decode_hw_header(interface->rbuf, 375221345Sdim interface->rbuf_offset, hfrom); 376221345Sdim 377221345Sdim /* 378221345Sdim * If a physical layer checksum failed (dunno of any 379226633Sdim * physical layer that supports this, but WTH), skip 380221345Sdim * this packet. 381221345Sdim */ 382221345Sdim if (offset < 0) { 383221345Sdim interface->rbuf_offset = 384221345Sdim BPF_WORDALIGN(interface->rbuf_offset + 385221345Sdim hdr.bh_caplen); 386221345Sdim continue; 387221345Sdim } 388226633Sdim interface->rbuf_offset += offset; 389221345Sdim hdr.bh_caplen -= offset; 390226633Sdim 391221345Sdim /* Decode the IP and UDP headers... */ 392221345Sdim offset = decode_udp_ip_header(interface->rbuf, 393239462Sdim interface->rbuf_offset, from, NULL, hdr.bh_caplen); 394198092Srdivacky 395198092Srdivacky /* If the IP or UDP checksum was bad, skip the packet... */ 396207619Srdivacky if (offset < 0) { 397212904Sdim interface->rbuf_offset = 398198092Srdivacky BPF_WORDALIGN(interface->rbuf_offset + 399212904Sdim hdr.bh_caplen); 400198092Srdivacky continue; 401201361Srdivacky } 402201361Srdivacky interface->rbuf_offset += offset; 403234353Sdim hdr.bh_caplen -= offset; 404239462Sdim 405234353Sdim /* 406234353Sdim * If there's not enough room to stash the packet data, 407224145Sdim * we have to skip it (this shouldn't happen in real 408224145Sdim * life, though). 409263508Sdim */ 410263508Sdim if (hdr.bh_caplen > len) { 411224145Sdim interface->rbuf_offset = 412234353Sdim BPF_WORDALIGN(interface->rbuf_offset + 413263508Sdim hdr.bh_caplen); 414263508Sdim continue; 415263508Sdim } 416263508Sdim 417263508Sdim /* Copy out the data in the packet... */ 418263508Sdim memcpy(buf, interface->rbuf + interface->rbuf_offset, 419263508Sdim hdr.bh_caplen); 420263508Sdim interface->rbuf_offset = 421263508Sdim BPF_WORDALIGN(interface->rbuf_offset + 422263508Sdim hdr.bh_caplen); 423263508Sdim return (hdr.bh_caplen); 424234353Sdim } while (!length); 425263508Sdim return (0); 426201361Srdivacky} 427263508Sdim