/* bpf.c 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 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 #include #include #include #include #include #include /* Reinitializes the specified interface after an address change. This is not required for packet-filter APIs. */ void if_reinitialize_send (info) struct interface_info *info; { } void if_reinitialize_receive (info) struct interface_info *info; { } /* 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 (info) struct interface_info *info; { int sock; char filename[50]; int 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 { if (!b) error ("No bpf devices.%s%s%s", " Please read the README", " section for your operating", " system."); 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 (info) 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; if (!quiet_interface_discovery) note ("Sending on BPF/%s/%s%s%s", info -> name, print_hw_addr (info -> hw_address.htype, info -> hw_address.hlen, info -> hw_address.haddr), (info -> shared_network ? "/" : ""), (info -> shared_network ? info -> shared_network -> name : "")); } /* 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! XXX */ 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); struct bpf_insn dhcp_bpf_tr_filter [] = { /* accept all token ring packets due to variable length header */ /* if we want to get clever, insert the program here */ /* 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_tr_filter_len = (sizeof dhcp_bpf_tr_filter / sizeof (struct bpf_insn)); void if_register_receive (info) struct interface_info *info; { int flag = 1, sz; struct bpf_version v; struct bpf_program p; /* 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! XXX */ dhcp_bpf_filter [8].k = ntohs (local_port); if (ioctl (info -> rfdesc, BIOCSETF, &p) < 0) error ("Can't install packet filter program: %m"); if (!quiet_interface_discovery) note ("Listening on BPF/%s/%s%s%s", info -> name, print_hw_addr (info -> hw_address.htype, info -> hw_address.hlen, info -> hw_address.haddr), (info -> shared_network ? "/" : ""), (info -> shared_network ? info -> shared_network -> name : "")); } ssize_t send_packet (interface, packet, raw, len, from, to, hto) 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; { int bufp = 0; unsigned char buf [256]; struct iovec iov [2]; int result; if (!strcmp (interface -> name, "fallback")) return send_fallback (interface, packet, raw, len, from, to, hto); /* 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 (interface, buf, len, from, hfrom) struct interface_info *interface; unsigned char *buf; size_t len; struct sockaddr_in *from; struct hardware *hfrom; { int length = 0; int 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, (unsigned char *)0, 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; } int can_unicast_without_arp () { return 1; } int can_receive_unicast_unconfigured (ip) struct interface_info *ip; { return 1; } void maybe_setup_fallback () { struct interface_info *fbi; fbi = setup_fallback (); if (fbi) { if_register_fallback (fbi); add_protocol ("fallback", fallback_interface -> wfdesc, fallback_discard, fallback_interface); } }