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https://github.com/pi-hole/dnsmasq.git
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import of dnsmasq-2.28.tar.gz
This commit is contained in:
Simon Kelley
238
src/bpf.c
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238
src/bpf.c
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/* dnsmasq is Copyright (c) 2000-2006 Simon Kelley
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 dated June, 1991.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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*/
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#include "dnsmasq.h"
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#ifndef HAVE_LINUX_NETWORK
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#include <net/bpf.h>
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static struct iovec ifconf = {
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.iov_base = NULL,
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.iov_len = 0
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};
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static struct iovec ifreq = {
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.iov_base = NULL,
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.iov_len = 0
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};
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struct header {
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struct ether_header ether;
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struct ip ip;
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struct udphdr {
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u16 uh_sport; /* source port */
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u16 uh_dport; /* destination port */
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u16 uh_ulen; /* udp length */
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u16 uh_sum; /* udp checksum */
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} udp;
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};
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void init_bpf(struct daemon *daemon)
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{
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int i = 0;
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while (1)
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{
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/* useful size which happens to be sufficient */
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if (expand_buf(&ifreq, sizeof(struct ifreq)))
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{
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sprintf(ifreq.iov_base, "/dev/bpf%d", i++);
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if ((daemon->dhcp_raw_fd = open(ifreq.iov_base, O_RDWR, 0)) != -1)
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return;
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}
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if (errno != EBUSY)
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die(_("cannot create DHCP BPF socket: %s"), NULL);
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}
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}
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void send_via_bpf(struct daemon *daemon, struct dhcp_packet *mess, size_t len,
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struct in_addr iface_addr, struct ifreq *ifr)
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{
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/* Hairy stuff, packet either has to go to the
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net broadcast or the destination can't reply to ARP yet,
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but we do know the physical address.
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Build the packet by steam, and send directly, bypassing
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the kernel IP stack */
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struct header header;
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u32 i, sum;
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struct iovec iov[2];
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/* Only know how to do ethernet on *BSD */
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if (mess->htype != ARPHRD_ETHER || mess->hlen != ETHER_ADDR_LEN)
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{
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syslog(LOG_WARNING, _("DHCP request for unsupported hardware type (%d) received on %s"),
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mess->htype, ifr->ifr_name);
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return;
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}
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ifr->ifr_addr.sa_family = AF_LINK;
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if (ioctl(daemon->dhcpfd, SIOCGIFADDR, ifr) < 0)
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return;
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memcpy(header.ether.ether_shost, LLADDR((struct sockaddr_dl *)&ifr->ifr_addr), ETHER_ADDR_LEN);
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header.ether.ether_type = htons(ETHERTYPE_IP);
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if (ntohs(mess->flags) & 0x8000)
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{
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memset(header.ether.ether_dhost, 255, ETHER_ADDR_LEN);
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header.ip.ip_dst.s_addr = INADDR_BROADCAST;
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}
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else
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{
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memcpy(header.ether.ether_dhost, mess->chaddr, ETHER_ADDR_LEN);
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header.ip.ip_dst.s_addr = mess->yiaddr.s_addr;
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}
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header.ip.ip_p = IPPROTO_UDP;
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header.ip.ip_src.s_addr = iface_addr.s_addr;
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header.ip.ip_len = htons(sizeof(struct ip) +
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sizeof(struct udphdr) +
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len) ;
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header.ip.ip_hl = sizeof(struct ip) / 4;
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header.ip.ip_v = IPVERSION;
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header.ip.ip_tos = 0;
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header.ip.ip_id = htons(0);
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header.ip.ip_off = htons(0x4000); /* don't fragment */
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header.ip.ip_ttl = IPDEFTTL;
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header.ip.ip_sum = 0;
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for (sum = 0, i = 0; i < sizeof(struct ip) / 2; i++)
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sum += ((u16 *)&header.ip)[i];
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while (sum>>16)
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sum = (sum & 0xffff) + (sum >> 16);
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header.ip.ip_sum = (sum == 0xffff) ? sum : ~sum;
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header.udp.uh_sport = htons(DHCP_SERVER_PORT);
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header.udp.uh_dport = htons(DHCP_CLIENT_PORT);
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if (len & 1)
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((char *)mess)[len] = 0; /* for checksum, in case length is odd. */
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header.udp.uh_sum = 0;
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header.udp.uh_ulen = sum = htons(sizeof(struct udphdr) + len);
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sum += htons(IPPROTO_UDP);
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for (i = 0; i < 4; i++)
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sum += ((u16 *)&header.ip.ip_src)[i];
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for (i = 0; i < sizeof(struct udphdr)/2; i++)
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sum += ((u16 *)&header.udp)[i];
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for (i = 0; i < (len + 1) / 2; i++)
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sum += ((u16 *)mess)[i];
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while (sum>>16)
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sum = (sum & 0xffff) + (sum >> 16);
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header.udp.uh_sum = (sum == 0xffff) ? sum : ~sum;
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ioctl(daemon->dhcp_raw_fd, BIOCSETIF, ifr);
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iov[0].iov_base = &header;
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iov[0].iov_len = sizeof(struct header);
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iov[1].iov_base = mess;
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iov[1].iov_len = len;
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while (writev(daemon->dhcp_raw_fd, iov, 2) == -1 && retry_send());
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}
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int iface_enumerate(struct daemon *daemon, void *parm, int (*ipv4_callback)(), int (*ipv6_callback)())
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{
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char *ptr;
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struct ifreq *ifr, ifaux;
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struct ifconf ifc;
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int fd, errsav, ret = 0;
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int lastlen = 0;
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size_t len;
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if ((fd = socket(PF_INET, SOCK_DGRAM, 0)) == -1)
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return 0;
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for (len = 0; ; len += 10*sizeof(struct ifreq))
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{
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if (!expand_buf(&ifconf, len))
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goto err;
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ifc.ifc_len = len;
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ifc.ifc_buf = ifconf.iov_base;
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if (ioctl(fd, SIOCGIFCONF, &ifc) == -1)
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{
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if (errno != EINVAL || lastlen != 0)
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goto err;
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}
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else
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{
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if (ifc.ifc_len == lastlen)
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break; /* got a big enough buffer now */
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lastlen = ifc.ifc_len;
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}
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}
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for (ptr = ifc.ifc_buf; ptr < ifc.ifc_buf + ifc.ifc_len; ptr += len )
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{
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/* subsequent entries may not be aligned, so copy into
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an aligned buffer to avoid nasty complaints about
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unaligned accesses. */
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#ifdef HAVE_SOCKADDR_SA_LEN
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len = ((struct ifreq *)ptr)->ifr_addr.sa_len + IF_NAMESIZE;
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#else
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len = sizeof(struct ifreq);
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#endif
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if (!expand_buf(&ifreq, len))
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goto err;
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ifr = ifreq.iov_base;
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memcpy(ifr, ptr, len);
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strncpy(ifaux.ifr_name, ifr->ifr_name, IF_NAMESIZE);
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if (ifr->ifr_addr.sa_family == AF_INET && ipv4_callback)
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{
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struct in_addr addr, netmask, broadcast;
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if (ioctl(fd, SIOCGIFINDEX, &ifaux) == -1)
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continue;
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broadcast.s_addr = 0;
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addr = ((struct sockaddr_in *) &ifr->ifr_addr)->sin_addr;
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if (ioctl(fd, SIOCGIFNETMASK, ifr) == -1)
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continue;
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netmask = ((struct sockaddr_in *) &ifr->ifr_addr)->sin_addr;
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if (ioctl(fd, SIOCGIFBRDADDR, ifr) != -1)
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broadcast = ((struct sockaddr_in *) &ifr->ifr_addr)->sin_addr;
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if (!((*ipv4_callback)(daemon, addr, (int)ifaux.ifr_index, netmask, broadcast, parm)))
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goto err;
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}
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#ifdef HAVE_IPV6
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else if (ifr->ifr_addr.sa_family == AF_INET6 && ipv6_callback)
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{
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struct in6_addr *addr = &((struct sockaddr_in6 *)&ifr->ifr_addr)->sin6_addr;
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/* voodoo to clear interface field in address */
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if (!(daemon->options & OPT_NOWILD) && IN6_IS_ADDR_LINKLOCAL(addr))
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{
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addr->s6_addr[2] = 0;
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addr->s6_addr[3] = 0;
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}
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if (ioctl(fd, SIOCGIFINDEX, &ifaux) == -1)
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continue;
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if (!((*ipv6_callback)(daemon, addr,
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(int)((struct sockaddr_in6 *)&ifr->ifr_addr)->sin6_scope_id,
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(int)ifaux.ifr_index,
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parm)))
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goto err;
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}
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#endif
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}
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ret = 1;
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err:
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errsav = errno;
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close(fd);
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errno = errsav;
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return ret;
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}
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#endif
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