/* $NetBSD: bpf.c,v 1.3.4.1 2024/02/29 11:39:17 martin Exp $ */ /* bpf.c BPF socket interface code, originally contributed by Archie Cobbs. */ /* * Copyright (C) 2004-2022 Internet Systems Consortium, Inc. ("ISC") * Copyright (c) 1996-2003 by Internet Software Consortium * * This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this * file, You can obtain one at http://mozilla.org/MPL/2.0/. * * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. * * Internet Systems Consortium, Inc. * PO Box 360 * Newmarket, NH 03857 USA * * https://www.isc.org/ * * This software was contributed to Internet Systems Consortium * by Archie Cobbs. * * Patches for FDDI support on Digital Unix were written by Bill * Stapleton, and maintained for a while by Mike Meredith before he * managed to get me to integrate them. */ #include __RCSID("$NetBSD: bpf.c,v 1.3.4.1 2024/02/29 11:39:17 martin Exp $"); #include "dhcpd.h" #if defined (USE_BPF_SEND) || defined (USE_BPF_RECEIVE) \ || defined (USE_LPF_RECEIVE) # if defined (USE_LPF_RECEIVE) # include # include # define bpf_insn sock_filter /* Linux: dare to be gratuitously different. */ # else # include # include # include # if defined (NEED_OSF_PFILT_HACKS) # include # endif # endif #include #include #include "includes/netinet/ip.h" #include "includes/netinet/udp.h" #include "includes/netinet/if_ether.h" #endif #if defined(USE_BPF_SEND) || defined(USE_BPF_RECEIVE) || defined(USE_BPF_HWADDR) #include #include #endif #include /* Reinitializes the specified interface after an address change. This is not required for packet-filter APIs. */ #ifdef USE_BPF_SEND void if_reinitialize_send (info) struct interface_info *info; { } #endif #ifdef USE_BPF_RECEIVE void if_reinitialize_receive (info) struct interface_info *info; { } #endif /* 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. */ #if defined (USE_BPF_SEND) || defined (USE_BPF_RECEIVE) 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++) { /* %Audit% 31 bytes max. %2004.06.17,Safe% */ sprintf(filename, BPF_FORMAT, b); sock = open (filename, O_RDWR, 0); if (sock < 0) { if (errno == EBUSY) { continue; } else { if (!b) log_fatal ("No bpf devices.%s%s%s", " Please read the README", " section for your operating", " system."); log_fatal ("Can't find free bpf: %m"); } } else { break; } } /* Set the BPF device to point at this interface. */ if (ioctl (sock, BIOCSETIF, info -> ifp) < 0) log_fatal ("Can't attach interface %s to bpf device %s: %m", info -> name, filename); get_hw_addr(info->name, &info->hw_address); return sock; } #endif /* USE_BPF_SEND || USE_BPF_RECEIVE */ #ifdef USE_BPF_SEND 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. */ #ifndef USE_BPF_RECEIVE info -> wfdesc = if_register_bpf (info, interface); #else info -> wfdesc = info -> rfdesc; #endif if (!quiet_interface_discovery) log_info ("Sending on BPF/%s/%s%s%s", info -> name, print_hw_addr (info -> hw_address.hbuf [0], info -> hw_address.hlen - 1, &info -> hw_address.hbuf [1]), (info -> shared_network ? "/" : ""), (info -> shared_network ? info -> shared_network -> name : "")); } void if_deregister_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. */ #ifndef USE_BPF_RECEIVE close (info -> wfdesc); #endif info -> wfdesc = -1; if (!quiet_interface_discovery) log_info ("Disabling output on BPF/%s/%s%s%s", info -> name, print_hw_addr (info -> hw_address.hbuf [0], info -> hw_address.hlen - 1, &info -> hw_address.hbuf [1]), (info -> shared_network ? "/" : ""), (info -> shared_network ? info -> shared_network -> name : "")); } #endif /* USE_BPF_SEND */ #if defined (USE_BPF_RECEIVE) || defined (USE_LPF_RECEIVE) /* 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), }; #if defined(RELAY_PORT) /* * For relay port extension */ struct bpf_insn dhcp_bpf_relay_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, 10), /* 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, 8), /* 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, 6, 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, 2, 0), /* patch */ /* relay can have an alternative 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_relay_filter_len = sizeof dhcp_bpf_relay_filter / sizeof (struct bpf_insn); #endif #if defined (DEC_FDDI) struct bpf_insn *bpf_fddi_filter = NULL; #endif int dhcp_bpf_filter_len = sizeof dhcp_bpf_filter / sizeof (struct bpf_insn); #if defined (HAVE_TR_SUPPORT) 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)); #endif /* HAVE_TR_SUPPORT */ #endif /* USE_LPF_RECEIVE || USE_BPF_RECEIVE */ #if defined (USE_BPF_RECEIVE) void if_register_receive (info) struct interface_info *info; { int flag = 1; struct bpf_version v; struct bpf_program p; #ifdef NEED_OSF_PFILT_HACKS u_int32_t bits; #endif #ifdef DEC_FDDI int link_layer; #endif /* DEC_FDDI */ /* 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) log_fatal ("Can't get BPF version: %m"); if (v.bv_major != BPF_MAJOR_VERSION || v.bv_minor < BPF_MINOR_VERSION) log_fatal ("BPF version mismatch - recompile DHCP!"); /* 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) log_fatal ("Can't set immediate mode on bpf device: %m"); #ifdef NEED_OSF_PFILT_HACKS /* Allow the copyall flag to be set... */ if (ioctl(info -> rfdesc, EIOCALLOWCOPYALL, &flag) < 0) log_fatal ("Can't set ALLOWCOPYALL: %m"); /* Clear all the packet filter mode bits first... */ bits = 0; if (ioctl (info -> rfdesc, EIOCMBIS, &bits) < 0) log_fatal ("Can't clear pfilt bits: %m"); /* Set the ENBATCH, ENCOPYALL, ENBPFHDR bits... */ bits = ENBATCH | ENCOPYALL | ENBPFHDR; if (ioctl (info -> rfdesc, EIOCMBIS, &bits) < 0) log_fatal ("Can't set ENBATCH|ENCOPYALL|ENBPFHDR: %m"); #endif /* Get the required BPF buffer length from the kernel. */ if (ioctl (info -> rfdesc, BIOCGBLEN, &info -> rbuf_max) < 0) log_fatal ("Can't get bpf buffer length: %m"); info -> rbuf = dmalloc (info -> rbuf_max, MDL); if (!info -> rbuf) log_fatal ("Can't allocate %ld bytes for bpf input buffer.", (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; #ifdef DEC_FDDI /* See if this is an FDDI interface, flag it for later. */ if (ioctl(info -> rfdesc, BIOCGDLT, &link_layer) >= 0 && link_layer == DLT_FDDI) { if (!bpf_fddi_filter) { bpf_fddi_filter = dmalloc (sizeof dhcp_bpf_filter, MDL); if (!bpf_fddi_filter) log_fatal ("No memory for FDDI filter."); memcpy (bpf_fddi_filter, dhcp_bpf_filter, sizeof dhcp_bpf_filter); /* Patch the BPF program to account for the difference in length between ethernet headers (14), FDDI and 802.2 headers (16 +8=24, +10). XXX changes to filter program may require changes to XXX the insn number(s) used below! */ bpf_fddi_filter[0].k += 10; bpf_fddi_filter[2].k += 10; bpf_fddi_filter[4].k += 10; bpf_fddi_filter[6].k += 10; bpf_fddi_filter[7].k += 10; } p.bf_insns = bpf_fddi_filter; } else #endif /* DEC_FDDI */ 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 */ #if defined(RELAY_PORT) if (relay_port) { /* * If user defined relay UDP port, we need to filter * also on the user UDP port. */ p.bf_len = dhcp_bpf_relay_filter_len; p.bf_insns = dhcp_bpf_relay_filter; dhcp_bpf_relay_filter [10].k = ntohs (relay_port); } #endif p.bf_insns [8].k = ntohs (*libdhcp_callbacks.local_port); if (ioctl (info -> rfdesc, BIOCSETF, &p) < 0) log_fatal ("Can't install packet filter program: %m"); if (!quiet_interface_discovery) log_info ("Listening on BPF/%s/%s%s%s", info -> name, print_hw_addr (info -> hw_address.hbuf [0], info -> hw_address.hlen - 1, &info -> hw_address.hbuf [1]), (info -> shared_network ? "/" : ""), (info -> shared_network ? info -> shared_network -> name : "")); } void if_deregister_receive (info) struct interface_info *info; { close (info -> rfdesc); info -> rfdesc = -1; if (!quiet_interface_discovery) log_info ("Disabling input on BPF/%s/%s%s%s", info -> name, print_hw_addr (info -> hw_address.hbuf [0], info -> hw_address.hlen - 1, &info -> hw_address.hbuf [1]), (info -> shared_network ? "/" : ""), (info -> shared_network ? info -> shared_network -> name : "")); } #endif /* USE_BPF_RECEIVE */ #ifdef USE_BPF_SEND 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; { unsigned hbufp = 0, ibufp = 0; double hw [4]; double ip [32]; struct iovec iov [3]; int result; if (!strcmp (interface -> name, "fallback")) return send_fallback (interface, packet, raw, len, from, to, hto); if (hto == NULL && interface->anycast_mac_addr.hlen) hto = &interface->anycast_mac_addr; /* Assemble the headers... */ assemble_hw_header (interface, (unsigned char *)hw, &hbufp, hto); assemble_udp_ip_header (interface, (unsigned char *)ip, &ibufp, from.s_addr, to -> sin_addr.s_addr, to -> sin_port, (unsigned char *)raw, len); /* Fire it off */ iov [0].iov_base = ((char *)hw); iov [0].iov_len = hbufp; iov [1].iov_base = ((char *)ip); iov [1].iov_len = ibufp; iov [2].iov_base = (char *)raw; iov [2].iov_len = len; result = writev(interface -> wfdesc, iov, 3); if (result < 0) log_error ("send_packet: %m"); return result; } #endif /* USE_BPF_SEND */ #ifdef USE_BPF_RECEIVE 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; unsigned paylen; /* 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... */ /* If the buffer is empty, fill it. */ if (interface->rbuf_offset >= interface->rbuf_len) { length = read(interface->rfdesc, interface->rbuf, (size_t)interface->rbuf_max); if (length <= 0) { #ifdef __FreeBSD__ if (errno == ENXIO) { #else if (errno == EIO) { #endif dhcp_interface_remove ((omapi_object_t *)interface, NULL); } return (length); } interface->rbuf_offset = 0; interface->rbuf_len = BPF_WORDALIGN(length); } do { /* 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 = BPF_WORDALIGN(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 = BPF_WORDALIGN(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, hdr.bh_caplen, &paylen, 1); /* If the IP or UDP checksum was bad, skip the packet... */ if (offset < 0) { interface->rbuf_offset = BPF_WORDALIGN(interface->rbuf_offset + hdr.bh_caplen); continue; } interface->rbuf_offset = 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 = BPF_WORDALIGN(interface->rbuf_offset + hdr.bh_caplen); continue; } /* Copy out the data in the packet... */ memcpy(buf, interface->rbuf + interface->rbuf_offset, paylen); interface->rbuf_offset = BPF_WORDALIGN(interface->rbuf_offset + hdr.bh_caplen); return paylen; } while (interface->rbuf_offset < interface->rbuf_len); return (0); } int can_unicast_without_arp (ip) struct interface_info *ip; { return 1; } int can_receive_unicast_unconfigured (ip) struct interface_info *ip; { return 1; } int supports_multiple_interfaces (ip) struct interface_info *ip; { return 1; } void maybe_setup_fallback () { isc_result_t status; struct interface_info *fbi = (struct interface_info *)0; if (setup_fallback (&fbi, MDL)) { if_register_fallback (fbi); status = omapi_register_io_object ((omapi_object_t *)fbi, if_readsocket, 0, fallback_discard, 0, 0); if (status != ISC_R_SUCCESS) log_fatal ("Can't register I/O handle for %s: %s", fbi -> name, isc_result_totext (status)); interface_dereference (&fbi, MDL); } } #endif #if defined(USE_BPF_RECEIVE) || defined(USE_BPF_HWADDR) static int lladdr_active(int s, const char *name, const struct ifaddrs *ifa) { if (ifa->ifa_addr->sa_family != AF_LINK) return 0; if (strcmp(ifa->ifa_name, name) != 0) return 0; #ifdef SIOCGLIFADDR { struct if_laddrreq iflr; const struct sockaddr_dl *sdl; sdl = satocsdl(ifa->ifa_addr); memset(&iflr, 0, sizeof(iflr)); strlcpy(iflr.iflr_name, ifa->ifa_name, sizeof(iflr.iflr_name)); memcpy(&iflr.addr, ifa->ifa_addr, MIN(ifa->ifa_addr->sa_len, sizeof(iflr.addr))); iflr.flags = IFLR_PREFIX; iflr.prefixlen = sdl->sdl_alen * NBBY; if (ioctl(s, SIOCGLIFADDR, &iflr) == -1) { log_fatal("ioctl(SIOCGLIFADDR): %m"); } if ((iflr.flags & IFLR_ACTIVE) == 0) return 0; } #endif return 1; } void get_hw_addr(const char *name, struct hardware *hw) { struct ifaddrs *ifa; struct ifaddrs *p; struct sockaddr_dl *sa; int s; if ((s = socket(AF_LINK, SOCK_DGRAM, 0)) == -1) { log_fatal("socket AF_LINK: %m"); } if (getifaddrs(&ifa) != 0) { log_fatal("Error getting interface information; %m"); } /* * Loop through our interfaces finding a match. */ sa = NULL; for (p=ifa; (p != NULL) && (sa == NULL); p = p->ifa_next) { if (lladdr_active(s, name, p)) { sa = (struct sockaddr_dl *)p->ifa_addr; break; } } if (sa == NULL) { log_fatal("No interface called '%s'", name); } close(s); /* * Pull out the appropriate information. */ switch (sa->sdl_type) { case IFT_ETHER: #ifdef IFT_CARP case IFT_CARP: #endif #if defined (IFT_L2VLAN) case IFT_L2VLAN: #endif hw->hlen = sa->sdl_alen + 1; hw->hbuf[0] = HTYPE_ETHER; memcpy(&hw->hbuf[1], LLADDR(sa), sa->sdl_alen); break; case IFT_ISO88023: case IFT_ISO88024: /* "token ring" */ case IFT_ISO88025: case IFT_ISO88026: hw->hlen = sa->sdl_alen + 1; hw->hbuf[0] = HTYPE_IEEE802; memcpy(&hw->hbuf[1], LLADDR(sa), sa->sdl_alen); break; #ifdef IFT_FDDI case IFT_FDDI: hw->hlen = sa->sdl_alen + 1; hw->hbuf[0] = HTYPE_FDDI; memcpy(&hw->hbuf[1], LLADDR(sa), sa->sdl_alen); break; #endif /* IFT_FDDI */ default: log_fatal("Unsupported device type %d for \"%s\"", sa->sdl_type, name); } freeifaddrs(ifa); } #endif