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- /*
- * Copyright (C) 2010 Felix Fietkau <nbd@openwrt.org>
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License v2 as published by
- * the Free Software Foundation.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
- */
- #define _GNU_SOURCE
- #include <sys/socket.h>
- #include <stdio.h>
- #include <string.h>
- #include <errno.h>
- #include <unistd.h>
- #include <fcntl.h>
- #include "relayd.h"
- struct ip_packet {
- struct ether_header eth;
- struct iphdr iph;
- } __packed;
- enum {
- DHCP_OPTION_ROUTER = 0x03,
- DHCP_OPTION_ROUTES = 0x79,
- DHCP_OPTION_END = 0xff,
- };
- struct dhcp_option {
- uint8_t code;
- uint8_t len;
- uint8_t data[];
- };
- struct dhcp_header {
- uint8_t op, htype, hlen, hops;
- uint32_t xit;
- uint16_t secs, flags;
- struct in_addr ciaddr, yiaddr, siaddr, giaddr;
- unsigned char chaddr[16];
- unsigned char sname[64];
- unsigned char file[128];
- uint32_t cookie;
- uint8_t option_data[];
- } __packed;
- static uint16_t
- chksum(uint16_t sum, const uint8_t *data, uint16_t len)
- {
- const uint8_t *last;
- uint16_t t;
- last = data + len - 1;
- while(data < last) {
- t = (data[0] << 8) + data[1];
- sum += t;
- if(sum < t)
- sum++;
- data += 2;
- }
- if(data == last) {
- t = (data[0] << 8) + 0;
- sum += t;
- if(sum < t)
- sum++;
- }
- return sum;
- }
- static void
- parse_dhcp_options(struct relayd_host *host, struct dhcp_header *dhcp, int len)
- {
- uint8_t *end = (uint8_t *) dhcp + len;
- struct dhcp_option *opt = (void *)dhcp->option_data;
- static const uint8_t dest[4] = { 0, 0, 0, 0 };
- while((uint8_t *) opt + sizeof(*opt) < end) {
- if ((uint8_t *) opt + opt->len > end ||
- (uint8_t *) opt + sizeof(*opt) > end )
- break;
- opt = (void *) &opt->data[opt->len];
- if ((uint8_t *) opt + sizeof(*opt) > end )
- break;
- switch(opt->code) {
- case DHCP_OPTION_ROUTER:
- DPRINTF(2, "Found a DHCP router option, len=%d\n", opt->len);
- if (!memcmp(opt->data, host->ipaddr, 4))
- relayd_add_host_route(host, dest, 0);
- else
- relayd_add_pending_route(opt->data, dest, 0, 10000);
- break;
- case DHCP_OPTION_ROUTES:
- DPRINTF(2, "Found a DHCP static routes option, len=%d\n", opt->len);
- break;
- case DHCP_OPTION_END:
- opt = (void *) end;
- continue;
- default:
- DPRINTF(3, "Skipping unknown DHCP option %02x\n", opt->code);
- continue;
- }
- }
- }
- bool relayd_handle_dhcp_packet(struct relayd_interface *rif, void *data, int len, bool forward, bool parse)
- {
- struct ip_packet *pkt = data;
- struct udphdr *udp;
- struct dhcp_header *dhcp;
- struct relayd_host *host;
- int udplen;
- uint16_t sum;
- if (pkt->eth.ether_type != htons(ETH_P_IP))
- return false;
- if (pkt->iph.version != 4)
- return false;
- if (pkt->iph.protocol != IPPROTO_UDP)
- return false;
- udp = (void *) ((char *) &pkt->iph + (pkt->iph.ihl << 2));
- dhcp = (void *) (udp + 1);
- if ((uint8_t *)udp + sizeof(*udp) > (uint8_t *)data + len ||
- (uint8_t *)dhcp + sizeof(*dhcp) > (uint8_t *)data + len)
- return false;
- udplen = ntohs(udp->len);
- if (udplen > len - ((char *) udp - (char *) data))
- return false;
- if (udp->dest != htons(67) && udp->source != htons(67))
- return false;
- if (dhcp->op != 1 && dhcp->op != 2)
- return false;
- if (!forward)
- return true;
- if (dhcp->op == 2) {
- host = relayd_refresh_host(rif, pkt->eth.ether_shost, (void *) &pkt->iph.saddr);
- if (host && parse)
- parse_dhcp_options(host, dhcp, udplen - sizeof(struct udphdr));
- }
- DPRINTF(2, "%s: handling DHCP %s\n", rif->ifname, (dhcp->op == 1 ? "request" : "response"));
- dhcp->flags |= htons(DHCP_FLAG_BROADCAST);
- udp->check = 0;
- sum = udplen + IPPROTO_UDP;
- sum = chksum(sum, (void *) &pkt->iph.saddr, 8);
- sum = chksum(sum, (void *) udp, udplen);
- if (sum == 0)
- sum = 0xffff;
- udp->check = htons(~sum);
- relayd_forward_bcast_packet(rif, data, len);
- return true;
- }
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