diff options
Diffstat (limited to 'usr.sbin/dhcrelay/bpf.c')
| -rw-r--r-- | usr.sbin/dhcrelay/bpf.c | 321 |
1 files changed, 321 insertions, 0 deletions
diff --git a/usr.sbin/dhcrelay/bpf.c b/usr.sbin/dhcrelay/bpf.c new file mode 100644 index 00000000000..657aad79af7 --- /dev/null +++ b/usr.sbin/dhcrelay/bpf.c @@ -0,0 +1,321 @@ +/* $OpenBSD: bpf.c,v 1.1 2004/04/12 21:10:28 henning Exp $ */ + +/* BPF socket interface code, originally contributed by Archie Cobbs. */ + +/* + * Copyright (c) 1995, 1996, 1998, 1999 + * The Internet Software Consortium. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. Neither the name of The Internet Software Consortium nor the names + * of its contributors may be used to endorse or promote products derived + * from this software without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND + * CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, + * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF + * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE + * DISCLAIMED. IN NO EVENT SHALL THE INTERNET SOFTWARE CONSORTIUM OR + * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF + * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND + * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, + * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT + * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + * + * This software has been written for the Internet Software Consortium + * by Ted Lemon <mellon@fugue.com> in cooperation with Vixie + * Enterprises. To learn more about the Internet Software Consortium, + * see ``http://www.vix.com/isc''. To learn more about Vixie + * Enterprises, see ``http://www.vix.com''. + */ + +#include "dhcpd.h" +#include <sys/ioctl.h> +#include <sys/uio.h> + +#include <net/bpf.h> +#include <netinet/in_systm.h> +#include <netinet/ip.h> +#include <netinet/udp.h> +#include <netinet/if_ether.h> + +#define BPF_FORMAT "/dev/bpf%d" + +/* + * Called by get_interface_list for each interface that's discovered. + * Opens a packet filter for each interface and adds it to the select + * mask. + */ +int +if_register_bpf(struct interface_info *info) +{ + char filename[50]; + int sock, b; + + /* Open a BPF device */ + for (b = 0; 1; b++) { + snprintf(filename, sizeof(filename), BPF_FORMAT, b); + sock = open(filename, O_RDWR, 0); + if (sock < 0) { + if (errno == EBUSY) + continue; + else + error("Can't find free bpf: %m"); + } else + break; + } + + /* Set the BPF device to point at this interface. */ + if (ioctl(sock, BIOCSETIF, info->ifp) < 0) + error("Can't attach interface %s to bpf device %s: %m", + info->name, filename); + + return (sock); +} + +void +if_register_send(struct interface_info *info) +{ + /* + * If we're using the bpf API for sending and receiving, we + * don't need to register this interface twice. + */ + info->wfdesc = info->rfdesc; +} + +/* + * Packet filter program... + * + * XXX: Changes to the filter program may require changes to the + * constant offsets used in if_register_send to patch the BPF program! + */ +struct bpf_insn dhcp_bpf_filter[] = { + /* Make sure this is an IP packet... */ + BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 12), + BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 8), + + /* Make sure it's a UDP packet... */ + BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 23), + BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 6), + + /* Make sure this isn't a fragment... */ + BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20), + BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 4, 0), + + /* Get the IP header length... */ + BPF_STMT(BPF_LDX + BPF_B + BPF_MSH, 14), + + /* Make sure it's to the right port... */ + BPF_STMT(BPF_LD + BPF_H + BPF_IND, 16), + BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 67, 0, 1), /* patch */ + + /* If we passed all the tests, ask for the whole packet. */ + BPF_STMT(BPF_RET+BPF_K, (u_int)-1), + + /* Otherwise, drop it. */ + BPF_STMT(BPF_RET+BPF_K, 0), +}; + +int dhcp_bpf_filter_len = sizeof(dhcp_bpf_filter) / sizeof(struct bpf_insn); + +void +if_register_receive(struct interface_info *info) +{ + struct bpf_version v; + struct bpf_program p; + int flag = 1, sz; + + /* Open a BPF device and hang it on this interface... */ + info->rfdesc = if_register_bpf(info); + + /* Make sure the BPF version is in range... */ + if (ioctl(info->rfdesc, BIOCVERSION, &v) < 0) + error("Can't get BPF version: %m"); + + if (v.bv_major != BPF_MAJOR_VERSION || + v.bv_minor < BPF_MINOR_VERSION) + error("Kernel BPF version out of range - recompile dhcpd!"); + + /* + * Set immediate mode so that reads return as soon as a packet + * comes in, rather than waiting for the input buffer to fill + * with packets. + */ + if (ioctl(info->rfdesc, BIOCIMMEDIATE, &flag) < 0) + error("Can't set immediate mode on bpf device: %m"); + + /* Get the required BPF buffer length from the kernel. */ + if (ioctl(info->rfdesc, BIOCGBLEN, &sz) < 0) + error("Can't get bpf buffer length: %m"); + info->rbuf_max = sz; + info->rbuf = malloc(info->rbuf_max); + if (!info->rbuf) + error("Can't allocate %lu bytes for bpf input buffer.", + (unsigned long)info->rbuf_max); + info->rbuf_offset = 0; + info->rbuf_len = 0; + + /* Set up the bpf filter program structure. */ + p.bf_len = dhcp_bpf_filter_len; + p.bf_insns = dhcp_bpf_filter; + + /* Patch the server port into the BPF program... + * + * XXX: changes to filter program may require changes to the + * insn number(s) used below! + */ + dhcp_bpf_filter[8].k = LOCAL_PORT; + + if (ioctl(info->rfdesc, BIOCSETF, &p) < 0) + error("Can't install packet filter program: %m"); +} + +ssize_t +send_packet(struct interface_info *interface, struct packet *packet, + struct dhcp_packet *raw, size_t len, struct in_addr from, + struct sockaddr_in *to, struct hardware *hto) +{ + unsigned char buf[256]; + struct iovec iov[2]; + int result, bufp = 0; + + /* Assemble the headers... */ + assemble_hw_header(interface, buf, &bufp, hto); + assemble_udp_ip_header(interface, buf, &bufp, from.s_addr, + to->sin_addr.s_addr, to->sin_port, (unsigned char *)raw, len); + + /* Fire it off */ + iov[0].iov_base = (char *)buf; + iov[0].iov_len = bufp; + iov[1].iov_base = (char *)raw; + iov[1].iov_len = len; + + result = writev(interface->wfdesc, iov, 2); + if (result < 0) + warn("send_packet: %m"); + return (result); +} + +ssize_t +receive_packet(struct interface_info *interface, unsigned char *buf, + size_t len, struct sockaddr_in *from, struct hardware *hfrom) +{ + int length = 0, offset = 0; + struct bpf_hdr hdr; + + /* + * All this complexity is because BPF doesn't guarantee that + * only one packet will be returned at a time. We're getting + * what we deserve, though - this is a terrible abuse of the BPF + * interface. Sigh. + */ + + /* Process packets until we get one we can return or until we've + * done a read and gotten nothing we can return... + */ + do { + /* If the buffer is empty, fill it. */ + if (interface->rbuf_offset == interface->rbuf_len) { + length = read(interface->rfdesc, interface->rbuf, + interface->rbuf_max); + if (length <= 0) + return (length); + interface->rbuf_offset = 0; + interface->rbuf_len = length; + } + + /* + * If there isn't room for a whole bpf header, something + * went wrong, but we'll ignore it and hope it goes + * away... XXX + */ + if (interface->rbuf_len - interface->rbuf_offset < + sizeof(hdr)) { + interface->rbuf_offset = interface->rbuf_len; + continue; + } + + /* Copy out a bpf header... */ + memcpy(&hdr, &interface->rbuf[interface->rbuf_offset], + sizeof(hdr)); + + /* + * If the bpf header plus data doesn't fit in what's + * left of the buffer, stick head in sand yet again... + */ + if (interface->rbuf_offset + hdr.bh_hdrlen + hdr.bh_caplen > + interface->rbuf_len) { + interface->rbuf_offset = interface->rbuf_len; + continue; + } + + /* + * If the captured data wasn't the whole packet, or if + * the packet won't fit in the input buffer, all we can + * do is drop it. + */ + if (hdr.bh_caplen != hdr.bh_datalen) { + interface->rbuf_offset += hdr.bh_hdrlen = hdr.bh_caplen; + continue; + } + + /* Skip over the BPF header... */ + interface->rbuf_offset += hdr.bh_hdrlen; + + /* Decode the physical header... */ + offset = decode_hw_header(interface, + interface->rbuf, interface->rbuf_offset, hfrom); + + /* + * If a physical layer checksum failed (dunno of any + * physical layer that supports this, but WTH), skip + * this packet. + */ + if (offset < 0) { + interface->rbuf_offset += hdr.bh_caplen; + continue; + } + interface->rbuf_offset += offset; + hdr.bh_caplen -= offset; + + /* Decode the IP and UDP headers... */ + offset = decode_udp_ip_header(interface, interface->rbuf, + interface->rbuf_offset, from, NULL, hdr.bh_caplen); + + /* If the IP or UDP checksum was bad, skip the packet... */ + if (offset < 0) { + interface->rbuf_offset += hdr.bh_caplen; + continue; + } + interface->rbuf_offset += offset; + hdr.bh_caplen -= offset; + + /* + * If there's not enough room to stash the packet data, + * we have to skip it (this shouldn't happen in real + * life, though). + */ + if (hdr.bh_caplen > len) { + interface->rbuf_offset += hdr.bh_caplen; + continue; + } + + /* Copy out the data in the packet... */ + memcpy(buf, interface->rbuf + interface->rbuf_offset, + hdr.bh_caplen); + interface->rbuf_offset += hdr.bh_caplen; + return (hdr.bh_caplen); + } while (!length); + return (0); +} |