bpf.c revision 148484
1147072Sbrooks/* $OpenBSD: bpf.c,v 1.13 2004/05/05 14:28:58 deraadt Exp $ */ 2147076Sbrooks/* $FreeBSD: head/sbin/dhclient/bpf.c 148484 2005-07-28 15:30:19Z brooks $ */ 3147072Sbrooks 4147072Sbrooks/* BPF socket interface code, originally contributed by Archie Cobbs. */ 5147072Sbrooks 6147072Sbrooks/* 7147072Sbrooks * Copyright (c) 1995, 1996, 1998, 1999 8147072Sbrooks * The Internet Software Consortium. All rights reserved. 9147072Sbrooks * 10147072Sbrooks * Redistribution and use in source and binary forms, with or without 11147072Sbrooks * modification, are permitted provided that the following conditions 12147072Sbrooks * are met: 13147072Sbrooks * 14147072Sbrooks * 1. Redistributions of source code must retain the above copyright 15147072Sbrooks * notice, this list of conditions and the following disclaimer. 16147072Sbrooks * 2. Redistributions in binary form must reproduce the above copyright 17147072Sbrooks * notice, this list of conditions and the following disclaimer in the 18147072Sbrooks * documentation and/or other materials provided with the distribution. 19147072Sbrooks * 3. Neither the name of The Internet Software Consortium nor the names 20147072Sbrooks * of its contributors may be used to endorse or promote products derived 21147072Sbrooks * from this software without specific prior written permission. 22147072Sbrooks * 23147072Sbrooks * THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND 24147072Sbrooks * CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, 25147072Sbrooks * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 26147072Sbrooks * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 27147072Sbrooks * DISCLAIMED. IN NO EVENT SHALL THE INTERNET SOFTWARE CONSORTIUM OR 28147072Sbrooks * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 29147072Sbrooks * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 30147072Sbrooks * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF 31147072Sbrooks * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND 32147072Sbrooks * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 33147072Sbrooks * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 34147072Sbrooks * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 35147072Sbrooks * SUCH DAMAGE. 36147072Sbrooks * 37147072Sbrooks * This software has been written for the Internet Software Consortium 38147072Sbrooks * by Ted Lemon <mellon@fugue.com> in cooperation with Vixie 39147072Sbrooks * Enterprises. To learn more about the Internet Software Consortium, 40147072Sbrooks * see ``http://www.vix.com/isc''. To learn more about Vixie 41147072Sbrooks * Enterprises, see ``http://www.vix.com''. 42147072Sbrooks */ 43147072Sbrooks 44147072Sbrooks#include "dhcpd.h" 45147072Sbrooks#include <sys/ioctl.h> 46147072Sbrooks#include <sys/uio.h> 47147072Sbrooks 48147072Sbrooks#include <net/bpf.h> 49147072Sbrooks#include <netinet/in_systm.h> 50147072Sbrooks#include <netinet/ip.h> 51147072Sbrooks#include <netinet/udp.h> 52147072Sbrooks#include <netinet/if_ether.h> 53147072Sbrooks 54147072Sbrooks#define BPF_FORMAT "/dev/bpf%d" 55147072Sbrooks 56147072Sbrooks/* 57147072Sbrooks * Called by get_interface_list for each interface that's discovered. 58147072Sbrooks * Opens a packet filter for each interface and adds it to the select 59147072Sbrooks * mask. 60147072Sbrooks */ 61147072Sbrooksint 62147072Sbrooksif_register_bpf(struct interface_info *info) 63147072Sbrooks{ 64147072Sbrooks char filename[50]; 65147072Sbrooks int sock, b; 66147072Sbrooks 67147072Sbrooks /* Open a BPF device */ 68147072Sbrooks for (b = 0; 1; b++) { 69147072Sbrooks snprintf(filename, sizeof(filename), BPF_FORMAT, b); 70147072Sbrooks sock = open(filename, O_RDWR, 0); 71147072Sbrooks if (sock < 0) { 72147072Sbrooks if (errno == EBUSY) 73147072Sbrooks continue; 74147072Sbrooks else 75147072Sbrooks error("Can't find free bpf: %m"); 76147072Sbrooks } else 77147072Sbrooks break; 78147072Sbrooks } 79147072Sbrooks 80147072Sbrooks /* Set the BPF device to point at this interface. */ 81147072Sbrooks if (ioctl(sock, BIOCSETIF, info->ifp) < 0) 82147072Sbrooks error("Can't attach interface %s to bpf device %s: %m", 83147072Sbrooks info->name, filename); 84147072Sbrooks 85147072Sbrooks return (sock); 86147072Sbrooks} 87147072Sbrooks 88147072Sbrooksvoid 89147072Sbrooksif_register_send(struct interface_info *info) 90147072Sbrooks{ 91147072Sbrooks /* 92147072Sbrooks * If we're using the bpf API for sending and receiving, we 93147072Sbrooks * don't need to register this interface twice. 94147072Sbrooks */ 95147072Sbrooks info->wfdesc = info->rfdesc; 96147072Sbrooks} 97147072Sbrooks 98147072Sbrooks/* 99147072Sbrooks * Packet filter program... 100147072Sbrooks * 101147072Sbrooks * XXX: Changes to the filter program may require changes to the 102147072Sbrooks * constant offsets used in if_register_send to patch the BPF program! 103147072Sbrooks */ 104147072Sbrooksstruct bpf_insn dhcp_bpf_filter[] = { 105147072Sbrooks /* Make sure this is an IP packet... */ 106147072Sbrooks BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 12), 107147072Sbrooks BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 8), 108147072Sbrooks 109147072Sbrooks /* Make sure it's a UDP packet... */ 110147072Sbrooks BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 23), 111147072Sbrooks BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 6), 112147072Sbrooks 113147072Sbrooks /* Make sure this isn't a fragment... */ 114147072Sbrooks BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20), 115147072Sbrooks BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 4, 0), 116147072Sbrooks 117147072Sbrooks /* Get the IP header length... */ 118147072Sbrooks BPF_STMT(BPF_LDX + BPF_B + BPF_MSH, 14), 119147072Sbrooks 120147072Sbrooks /* Make sure it's to the right port... */ 121147072Sbrooks BPF_STMT(BPF_LD + BPF_H + BPF_IND, 16), 122147072Sbrooks BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 67, 0, 1), /* patch */ 123147072Sbrooks 124147072Sbrooks /* If we passed all the tests, ask for the whole packet. */ 125147072Sbrooks BPF_STMT(BPF_RET+BPF_K, (u_int)-1), 126147072Sbrooks 127147072Sbrooks /* Otherwise, drop it. */ 128147072Sbrooks BPF_STMT(BPF_RET+BPF_K, 0), 129147072Sbrooks}; 130147072Sbrooks 131147072Sbrooksint dhcp_bpf_filter_len = sizeof(dhcp_bpf_filter) / sizeof(struct bpf_insn); 132147072Sbrooks 133147072Sbrooks/* 134147072Sbrooks * Packet write filter program: 135147072Sbrooks * 'ip and udp and src port bootps and dst port (bootps or bootpc)' 136147072Sbrooks */ 137147072Sbrooksstruct bpf_insn dhcp_bpf_wfilter[] = { 138147072Sbrooks BPF_STMT(BPF_LD + BPF_B + BPF_IND, 14), 139147072Sbrooks BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, (IPVERSION << 4) + 5, 0, 12), 140147072Sbrooks 141147072Sbrooks /* Make sure this is an IP packet... */ 142147072Sbrooks BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 12), 143147072Sbrooks BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 10), 144147072Sbrooks 145147072Sbrooks /* Make sure it's a UDP packet... */ 146147072Sbrooks BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 23), 147147072Sbrooks BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 8), 148147072Sbrooks 149147072Sbrooks /* Make sure this isn't a fragment... */ 150147072Sbrooks BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20), 151147072Sbrooks BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 6, 0), /* patched */ 152147072Sbrooks 153147072Sbrooks /* Get the IP header length... */ 154147072Sbrooks BPF_STMT(BPF_LDX + BPF_B + BPF_MSH, 14), 155147072Sbrooks 156147072Sbrooks /* Make sure it's from the right port... */ 157147072Sbrooks BPF_STMT(BPF_LD + BPF_H + BPF_IND, 14), 158147072Sbrooks BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 68, 0, 3), 159147072Sbrooks 160147072Sbrooks /* Make sure it is to the right ports ... */ 161147072Sbrooks BPF_STMT(BPF_LD + BPF_H + BPF_IND, 16), 162147072Sbrooks BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 67, 0, 1), 163147072Sbrooks 164147072Sbrooks /* If we passed all the tests, ask for the whole packet. */ 165147072Sbrooks BPF_STMT(BPF_RET+BPF_K, (u_int)-1), 166147072Sbrooks 167147072Sbrooks /* Otherwise, drop it. */ 168147072Sbrooks BPF_STMT(BPF_RET+BPF_K, 0), 169147072Sbrooks}; 170147072Sbrooks 171147072Sbrooksint dhcp_bpf_wfilter_len = sizeof(dhcp_bpf_wfilter) / sizeof(struct bpf_insn); 172147072Sbrooks 173147072Sbrooksvoid 174147072Sbrooksif_register_receive(struct interface_info *info) 175147072Sbrooks{ 176147072Sbrooks struct bpf_version v; 177147072Sbrooks struct bpf_program p; 178147072Sbrooks int flag = 1, sz; 179147072Sbrooks 180147072Sbrooks /* Open a BPF device and hang it on this interface... */ 181147072Sbrooks info->rfdesc = if_register_bpf(info); 182147072Sbrooks 183147072Sbrooks /* Make sure the BPF version is in range... */ 184147072Sbrooks if (ioctl(info->rfdesc, BIOCVERSION, &v) < 0) 185147072Sbrooks error("Can't get BPF version: %m"); 186147072Sbrooks 187147072Sbrooks if (v.bv_major != BPF_MAJOR_VERSION || 188147072Sbrooks v.bv_minor < BPF_MINOR_VERSION) 189147072Sbrooks error("Kernel BPF version out of range - recompile dhcpd!"); 190147072Sbrooks 191147072Sbrooks /* 192147072Sbrooks * Set immediate mode so that reads return as soon as a packet 193147072Sbrooks * comes in, rather than waiting for the input buffer to fill 194147072Sbrooks * with packets. 195147072Sbrooks */ 196147072Sbrooks if (ioctl(info->rfdesc, BIOCIMMEDIATE, &flag) < 0) 197147072Sbrooks error("Can't set immediate mode on bpf device: %m"); 198147072Sbrooks 199147072Sbrooks /* Get the required BPF buffer length from the kernel. */ 200147072Sbrooks if (ioctl(info->rfdesc, BIOCGBLEN, &sz) < 0) 201147072Sbrooks error("Can't get bpf buffer length: %m"); 202147072Sbrooks info->rbuf_max = sz; 203147072Sbrooks info->rbuf = malloc(info->rbuf_max); 204147072Sbrooks if (!info->rbuf) 205147072Sbrooks error("Can't allocate %lu bytes for bpf input buffer.", 206147072Sbrooks (unsigned long)info->rbuf_max); 207147072Sbrooks info->rbuf_offset = 0; 208147072Sbrooks info->rbuf_len = 0; 209147072Sbrooks 210147072Sbrooks /* Set up the bpf filter program structure. */ 211147072Sbrooks p.bf_len = dhcp_bpf_filter_len; 212147072Sbrooks p.bf_insns = dhcp_bpf_filter; 213147072Sbrooks 214147072Sbrooks /* Patch the server port into the BPF program... 215147072Sbrooks * 216147072Sbrooks * XXX: changes to filter program may require changes to the 217147072Sbrooks * insn number(s) used below! 218147072Sbrooks */ 219147072Sbrooks dhcp_bpf_filter[8].k = LOCAL_PORT; 220147072Sbrooks 221147072Sbrooks if (ioctl(info->rfdesc, BIOCSETF, &p) < 0) 222147072Sbrooks error("Can't install packet filter program: %m"); 223147072Sbrooks 224147076Sbrooks#ifdef BIOCSETWF 225147072Sbrooks /* Set up the bpf write filter program structure. */ 226147072Sbrooks p.bf_len = dhcp_bpf_wfilter_len; 227147072Sbrooks p.bf_insns = dhcp_bpf_wfilter; 228147072Sbrooks 229147072Sbrooks if (dhcp_bpf_wfilter[7].k == 0x1fff) 230147072Sbrooks dhcp_bpf_wfilter[7].k = htons(IP_MF|IP_OFFMASK); 231147072Sbrooks 232147072Sbrooks if (ioctl(info->rfdesc, BIOCSETWF, &p) < 0) 233147072Sbrooks error("Can't install write filter program: %m"); 234147072Sbrooks 235147072Sbrooks if (ioctl(info->rfdesc, BIOCLOCK, NULL) < 0) 236147072Sbrooks error("Cannot lock bpf"); 237147076Sbrooks#endif 238147072Sbrooks} 239147072Sbrooks 240147072Sbrooksssize_t 241147072Sbrookssend_packet(struct interface_info *interface, struct dhcp_packet *raw, 242147072Sbrooks size_t len, struct in_addr from, struct sockaddr_in *to, 243147072Sbrooks struct hardware *hto) 244147072Sbrooks{ 245147072Sbrooks unsigned char buf[256]; 246147072Sbrooks struct iovec iov[2]; 247147072Sbrooks int result, bufp = 0; 248147072Sbrooks 249147072Sbrooks /* Assemble the headers... */ 250147072Sbrooks assemble_hw_header(interface, buf, &bufp, hto); 251147072Sbrooks assemble_udp_ip_header(buf, &bufp, from.s_addr, 252147072Sbrooks to->sin_addr.s_addr, to->sin_port, (unsigned char *)raw, len); 253147072Sbrooks 254147072Sbrooks /* Fire it off */ 255147072Sbrooks iov[0].iov_base = (char *)buf; 256147072Sbrooks iov[0].iov_len = bufp; 257147072Sbrooks iov[1].iov_base = (char *)raw; 258147072Sbrooks iov[1].iov_len = len; 259147072Sbrooks 260147072Sbrooks result = writev(interface->wfdesc, iov, 2); 261147072Sbrooks if (result < 0) 262147072Sbrooks warning("send_packet: %m"); 263147072Sbrooks return (result); 264147072Sbrooks} 265147072Sbrooks 266147072Sbrooksssize_t 267147072Sbrooksreceive_packet(struct interface_info *interface, unsigned char *buf, 268147072Sbrooks size_t len, struct sockaddr_in *from, struct hardware *hfrom) 269147072Sbrooks{ 270147072Sbrooks int length = 0, offset = 0; 271147072Sbrooks struct bpf_hdr hdr; 272147072Sbrooks 273147072Sbrooks /* 274147072Sbrooks * All this complexity is because BPF doesn't guarantee that 275147072Sbrooks * only one packet will be returned at a time. We're getting 276147072Sbrooks * what we deserve, though - this is a terrible abuse of the BPF 277147072Sbrooks * interface. Sigh. 278147072Sbrooks */ 279147072Sbrooks 280147072Sbrooks /* Process packets until we get one we can return or until we've 281147072Sbrooks * done a read and gotten nothing we can return... 282147072Sbrooks */ 283147072Sbrooks do { 284147072Sbrooks /* If the buffer is empty, fill it. */ 285147072Sbrooks if (interface->rbuf_offset == interface->rbuf_len) { 286147072Sbrooks length = read(interface->rfdesc, interface->rbuf, 287147072Sbrooks interface->rbuf_max); 288147072Sbrooks if (length <= 0) 289147072Sbrooks return (length); 290147072Sbrooks interface->rbuf_offset = 0; 291147072Sbrooks interface->rbuf_len = length; 292147072Sbrooks } 293147072Sbrooks 294147072Sbrooks /* 295147072Sbrooks * If there isn't room for a whole bpf header, something 296147072Sbrooks * went wrong, but we'll ignore it and hope it goes 297147072Sbrooks * away... XXX 298147072Sbrooks */ 299147072Sbrooks if (interface->rbuf_len - interface->rbuf_offset < 300147072Sbrooks sizeof(hdr)) { 301147072Sbrooks interface->rbuf_offset = interface->rbuf_len; 302147072Sbrooks continue; 303147072Sbrooks } 304147072Sbrooks 305147072Sbrooks /* Copy out a bpf header... */ 306147072Sbrooks memcpy(&hdr, &interface->rbuf[interface->rbuf_offset], 307147072Sbrooks sizeof(hdr)); 308147072Sbrooks 309147072Sbrooks /* 310147072Sbrooks * If the bpf header plus data doesn't fit in what's 311147072Sbrooks * left of the buffer, stick head in sand yet again... 312147072Sbrooks */ 313147072Sbrooks if (interface->rbuf_offset + hdr.bh_hdrlen + hdr.bh_caplen > 314147072Sbrooks interface->rbuf_len) { 315147072Sbrooks interface->rbuf_offset = interface->rbuf_len; 316147072Sbrooks continue; 317147072Sbrooks } 318147072Sbrooks 319148451Sbrooks /* Skip over the BPF header... */ 320148451Sbrooks interface->rbuf_offset += hdr.bh_hdrlen; 321148451Sbrooks 322147072Sbrooks /* 323147072Sbrooks * If the captured data wasn't the whole packet, or if 324147072Sbrooks * the packet won't fit in the input buffer, all we can 325147072Sbrooks * do is drop it. 326147072Sbrooks */ 327147072Sbrooks if (hdr.bh_caplen != hdr.bh_datalen) { 328148484Sbrooks interface->rbuf_offset = 329148484Sbrooks BPF_WORDALIGN(interface->rbuf_offset + 330148484Sbrooks hdr.bh_caplen); 331147072Sbrooks continue; 332147072Sbrooks } 333147072Sbrooks 334147072Sbrooks /* Decode the physical header... */ 335147072Sbrooks offset = decode_hw_header(interface->rbuf, 336147072Sbrooks interface->rbuf_offset, hfrom); 337147072Sbrooks 338147072Sbrooks /* 339147072Sbrooks * If a physical layer checksum failed (dunno of any 340147072Sbrooks * physical layer that supports this, but WTH), skip 341147072Sbrooks * this packet. 342147072Sbrooks */ 343147072Sbrooks if (offset < 0) { 344148484Sbrooks interface->rbuf_offset = 345148484Sbrooks BPF_WORDALIGN(interface->rbuf_offset + 346148484Sbrooks hdr.bh_caplen); 347147072Sbrooks continue; 348147072Sbrooks } 349147072Sbrooks interface->rbuf_offset += offset; 350147072Sbrooks hdr.bh_caplen -= offset; 351147072Sbrooks 352147072Sbrooks /* Decode the IP and UDP headers... */ 353147072Sbrooks offset = decode_udp_ip_header(interface->rbuf, 354147072Sbrooks interface->rbuf_offset, from, NULL, hdr.bh_caplen); 355147072Sbrooks 356147072Sbrooks /* If the IP or UDP checksum was bad, skip the packet... */ 357147072Sbrooks if (offset < 0) { 358148484Sbrooks interface->rbuf_offset = 359148484Sbrooks BPF_WORDALIGN(interface->rbuf_offset + 360148484Sbrooks hdr.bh_caplen); 361147072Sbrooks continue; 362147072Sbrooks } 363147072Sbrooks interface->rbuf_offset += offset; 364147072Sbrooks hdr.bh_caplen -= offset; 365147072Sbrooks 366147072Sbrooks /* 367147072Sbrooks * If there's not enough room to stash the packet data, 368147072Sbrooks * we have to skip it (this shouldn't happen in real 369147072Sbrooks * life, though). 370147072Sbrooks */ 371147072Sbrooks if (hdr.bh_caplen > len) { 372148484Sbrooks interface->rbuf_offset = 373148484Sbrooks BPF_WORDALIGN(interface->rbuf_offset + 374148484Sbrooks hdr.bh_caplen); 375147072Sbrooks continue; 376147072Sbrooks } 377147072Sbrooks 378147072Sbrooks /* Copy out the data in the packet... */ 379147072Sbrooks memcpy(buf, interface->rbuf + interface->rbuf_offset, 380147072Sbrooks hdr.bh_caplen); 381148484Sbrooks interface->rbuf_offset = 382148484Sbrooks BPF_WORDALIGN(interface->rbuf_offset + 383148484Sbrooks hdr.bh_caplen); 384147072Sbrooks return (hdr.bh_caplen); 385147072Sbrooks } while (!length); 386147072Sbrooks return (0); 387147072Sbrooks} 388