Initial commit

1 files changed, 508 insertions, 0 deletions

diff --git a/src/dhcpv4.c b/src/dhcpv4.c
new file mode 100644
index 0000000..38b4f9b
--- /dev/null
+++ b/src/dhcpv4.c
@@ -0,0 +1,508 @@
+/**
+ * Copyright (C) 2012-2013 Steven Barth <steven@midlink.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.
+ *
+ *
+ */
+
+#include <time.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <resolv.h>
+#include <net/if.h>
+#include <net/if_arp.h>
+#include <netinet/ip.h>
+#include <sys/ioctl.h>
+#include <sys/timerfd.h>
+#include <arpa/inet.h>
+
+#include "odhcpd.h"
+#include "dhcpv4.h"
+#include "dhcpv6.h"
+
+
+static void handle_dhcpv4(void *addr, void *data, size_t len,
+		struct interface *iface);
+static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
+		enum dhcpv4_msg msg, const uint8_t *mac, struct in_addr reqaddr,
+		const char *hostname);
+
+
+// Create socket and register events
+int init_dhcpv4(void)
+{
+	return 0;
+}
+
+
+int setup_dhcpv4_interface(struct interface *iface, bool enable)
+{
+	if (iface->dhcpv4_event.uloop.fd > 0) {
+		close(iface->dhcpv4_event.uloop.fd);
+		iface->dhcpv4_event.uloop.fd = -1;
+	}
+
+	if (iface->dhcpv4 && enable) {
+		if (!iface->dhcpv4_assignments.next)
+			INIT_LIST_HEAD(&iface->dhcpv4_assignments);
+
+		int sock = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC, IPPROTO_UDP);
+
+		// Basic IPv6 configuration
+		int val = 1;
+		setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val));
+		setsockopt(sock, SOL_SOCKET, SO_BROADCAST, &val, sizeof(val));
+		setsockopt(sock, IPPROTO_IP, IP_PKTINFO, &val, sizeof(val));
+
+		val = IPTOS_CLASS_CS6;
+		setsockopt(sock, IPPROTO_IP, IP_TOS, &val, sizeof(val));
+
+		val = IP_PMTUDISC_DONT;
+		setsockopt(sock, IPPROTO_IP, IP_MTU_DISCOVER, &val, sizeof(val));
+
+		setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE,
+				iface->ifname, strlen(iface->ifname));
+
+		struct sockaddr_in bind_addr = {AF_INET, htons(DHCPV4_SERVER_PORT),
+					{INADDR_ANY}, {0}};
+
+		if (bind(sock, (struct sockaddr*)&bind_addr, sizeof(bind_addr))) {
+			syslog(LOG_ERR, "Failed to open DHCPv4 server socket: %s",
+					strerror(errno));
+			return -1;
+		}
+
+
+		if (ntohl(iface->dhcpv4_start.s_addr) > ntohl(iface->dhcpv4_end.s_addr)) {
+			syslog(LOG_ERR, "Invalid DHCP range");
+			return -1;
+		}
+
+		// Create a range if not specified
+		struct ifreq ifreq;
+		strncpy(ifreq.ifr_name, iface->ifname, sizeof(ifreq.ifr_name));
+
+		struct sockaddr_in *saddr = (struct sockaddr_in*)&ifreq.ifr_addr;
+		struct sockaddr_in *smask = (struct sockaddr_in*)&ifreq.ifr_netmask;
+		if (!(iface->dhcpv4_start.s_addr & htonl(0xffff0000)) &&
+				!(iface->dhcpv4_end.s_addr & htonl(0xffff0000)) &&
+				!ioctl(sock, SIOCGIFADDR, &ifreq)) {
+			struct in_addr addr = saddr->sin_addr;
+
+			ioctl(sock, SIOCGIFNETMASK, &ifreq);
+			struct in_addr mask = smask->sin_addr;
+
+			uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
+			uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
+
+			if (start && end && start < end &&
+					start > ntohl(addr.s_addr & ~mask.s_addr) &&
+					(start & ntohl(mask.s_addr)) == start &&
+					(end & ntohl(mask.s_addr)) == end) {
+				iface->dhcpv4_start.s_addr = htonl(start) |
+						(addr.s_addr & mask.s_addr);
+				iface->dhcpv4_end.s_addr = htonl(end) |
+						(addr.s_addr & mask.s_addr);
+			} else if (ntohl(mask.s_addr) <= 0xffffffc0) {
+				start = addr.s_addr & mask.s_addr;
+				end = addr.s_addr & mask.s_addr;
+
+				if (ntohl(mask.s_addr) <= 0xffffff00) {
+					iface->dhcpv4_start.s_addr = start | htonl(20);
+					iface->dhcpv4_end.s_addr = end | htonl(199);
+				} else {
+					iface->dhcpv4_start.s_addr = start | htonl(10);
+					iface->dhcpv4_end.s_addr = end | htonl(59);
+				}
+			}
+
+
+		}
+
+		// Parse static entries
+		struct lease *lease;
+		list_for_each_entry(lease, &leases, head) {
+			// Construct entry
+			size_t hostlen = strlen(lease->hostname) + 1;
+			struct dhcpv4_assignment *a = calloc(1, sizeof(*a) + hostlen);
+
+			a->addr = ntohl(lease->ipaddr.s_addr);
+			memcpy(a->hwaddr, lease->mac.ether_addr_octet, sizeof(a->hwaddr));
+			memcpy(a->hostname, lease->hostname, hostlen);
+
+			// Assign to all interfaces
+			struct dhcpv4_assignment *c;
+			list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
+				if (c->addr > a->addr) {
+					list_add_tail(&a->head, &c->head);
+				} else if (c->addr == a->addr) {
+					// Already an assignment with that number
+					break;
+				}
+			}
+
+			if (!a->head.next)
+				free(a);
+		}
+
+		// Clean invalid assignments
+		struct dhcpv4_assignment *a, *n;
+		list_for_each_entry_safe(a, n, &iface->dhcpv4_assignments, head) {
+			if ((htonl(a->addr) & smask->sin_addr.s_addr) !=
+					(saddr->sin_addr.s_addr & smask->sin_addr.s_addr)) {
+				list_del(&a->head);
+				free(a);
+			}
+		}
+
+
+		if (iface->dhcpv4_leasetime < 60)
+			iface->dhcpv4_leasetime = 1800;
+
+		iface->dhcpv4_event.uloop.fd = sock;
+		iface->dhcpv4_event.handle_dgram = handle_dhcpv4;
+		odhcpd_register(&iface->dhcpv4_event);
+	} else if (iface->dhcpv4_assignments.next) {
+		while (!list_empty(&iface->dhcpv4_assignments)) {
+			struct dhcpv4_assignment *a = list_first_entry(&iface->dhcpv4_assignments,
+					struct dhcpv4_assignment, head);
+			list_del(&a->head);
+			free(a->hostname);
+			free(a);
+		}
+
+	}
+	return 0;
+}
+
+
+static void dhcpv4_put(struct dhcpv4_message *msg, uint8_t **cookie,
+		uint8_t type, uint8_t len, const void *data)
+{
+	uint8_t *c = *cookie;
+	if (*cookie + 2 + len > (uint8_t*)&msg[1])
+		return;
+
+	*c++ = type;
+	*c++ = len;
+	memcpy(c, data, len);
+
+	*cookie = c + len;
+}
+
+
+// Simple DHCPv6-server for information requests
+static void handle_dhcpv4(void *addr, void *data, size_t len,
+		struct interface *iface)
+{
+	if (!iface->dhcpv4)
+		return;
+
+	struct dhcpv4_message *req = data;
+	if (len < offsetof(struct dhcpv4_message, options) + 4 ||
+			req->op != DHCPV4_BOOTREQUEST || req->hlen != 6)
+		return;
+
+	int sock = iface->dhcpv4_event.uloop.fd;
+	struct sockaddr_in ifaddr;
+	struct sockaddr_in ifnetmask;
+
+	syslog(LOG_NOTICE, "Got DHCPv4 request");
+
+	struct ifreq ifreq;
+	memcpy(ifreq.ifr_name, iface->ifname, sizeof(ifreq.ifr_name));
+	if (ioctl(sock, SIOCGIFADDR, &ifreq)) {
+		syslog(LOG_WARNING, "DHCPv4 failed to detect address: %s", strerror(errno));
+		return;
+	}
+
+	memcpy(&ifaddr, &ifreq.ifr_addr, sizeof(ifaddr));
+	if (ioctl(sock, SIOCGIFNETMASK, &ifreq))
+		return;
+
+	memcpy(&ifnetmask, &ifreq.ifr_netmask, sizeof(ifnetmask));
+	uint32_t network = ifaddr.sin_addr.s_addr & ifnetmask.sin_addr.s_addr;
+
+	if ((iface->dhcpv4_start.s_addr & ifnetmask.sin_addr.s_addr) != network ||
+			(iface->dhcpv4_end.s_addr & ifnetmask.sin_addr.s_addr) != network) {
+		syslog(LOG_WARNING, "DHCPv4 range out of assigned network");
+		return;
+	}
+
+	struct ifreq ifr = {.ifr_name = ""};
+	strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name));
+
+	struct dhcpv4_message reply = {
+		.op = DHCPV4_BOOTREPLY,
+		.htype = 1,
+		.hlen = 6,
+		.hops = 0,
+		.xid = req->xid,
+		.secs = 0,
+		.flags = req->flags,
+		.ciaddr = {INADDR_ANY},
+		.giaddr = req->giaddr,
+		.siaddr = ifaddr.sin_addr,
+	};
+	memcpy(reply.chaddr, req->chaddr, sizeof(reply.chaddr));
+
+	reply.options[0] = 0x63;
+	reply.options[1] = 0x82;
+	reply.options[2] = 0x53;
+	reply.options[3] = 0x63;
+
+	uint8_t *cookie = &reply.options[4];
+	uint8_t reqmsg = DHCPV4_MSG_REQUEST;
+	uint8_t msg = DHCPV4_MSG_ACK;
+
+	struct in_addr reqaddr = {INADDR_ANY};
+	char hostname[256];
+	hostname[0] = 0;
+
+	uint8_t *start = &req->options[4];
+	uint8_t *end = ((uint8_t*)data) + len;
+	struct dhcpv4_option *opt;
+	dhcpv4_for_each_option(start, end, opt) {
+		if (opt->type == DHCPV4_OPT_MESSAGE && opt->len == 1) {
+			reqmsg = opt->data[0];
+		} else if (opt->type == DHCPV4_OPT_HOSTNAME && opt->len > 0) {
+			memcpy(hostname, opt->data, opt->len);
+			hostname[opt->len] = 0;
+		} else if (opt->type == DHCPV4_OPT_IPADDRESS && opt->len == 4) {
+			memcpy(&reqaddr, opt->data, 4);
+		} else if (opt->type == DHCPV4_OPT_SERVERID && opt->len == 4) {
+			if (memcmp(opt->data, &ifaddr.sin_addr, 4))
+				return;
+		}
+	}
+
+	if (reqmsg != DHCPV4_MSG_DISCOVER && reqmsg != DHCPV4_MSG_REQUEST &&
+			reqmsg != DHCPV4_MSG_INFORM && reqmsg != DHCPV4_MSG_DECLINE &&
+			reqmsg != DHCPV4_MSG_RELEASE)
+		return;
+
+	struct dhcpv4_assignment *lease = NULL;
+	if (reqmsg != DHCPV4_MSG_INFORM)
+		lease = dhcpv4_lease(iface, reqmsg, req->chaddr, reqaddr, hostname);
+
+	if (!lease) {
+		if (reqmsg == DHCPV4_MSG_REQUEST)
+			msg = DHCPV4_MSG_NAK;
+		else if (reqmsg == DHCPV4_MSG_DISCOVER)
+			return;
+	} else if (reqmsg == DHCPV4_MSG_DISCOVER) {
+		msg = DHCPV4_MSG_OFFER;
+	}
+
+	if (reqmsg == DHCPV4_MSG_DECLINE || reqmsg == DHCPV4_MSG_RELEASE)
+		return;
+
+	dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MESSAGE, 1, &msg);
+	dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SERVERID, 4, &ifaddr.sin_addr);
+
+	if (lease) {
+		reply.yiaddr.s_addr = htonl(lease->addr);
+
+		uint32_t val = htonl(iface->dhcpv4_leasetime);
+		dhcpv4_put(&reply, &cookie, DHCPV4_OPT_LEASETIME, 4, &val);
+
+		val = htonl(500 * iface->dhcpv4_leasetime / 1000);
+		dhcpv4_put(&reply, &cookie, DHCPV4_OPT_RENEW, 4, &val);
+
+		val = htonl(875 * iface->dhcpv4_leasetime / 1000);
+		dhcpv4_put(&reply, &cookie, DHCPV4_OPT_REBIND, 4, &val);
+
+		dhcpv4_put(&reply, &cookie, DHCPV4_OPT_NETMASK, 4, &ifnetmask.sin_addr);
+
+		if (lease->hostname[0])
+			dhcpv4_put(&reply, &cookie, DHCPV4_OPT_HOSTNAME,
+					strlen(lease->hostname), lease->hostname);
+
+		if (!ioctl(sock, SIOCGIFBRDADDR, &ifr)) {
+			struct sockaddr_in *ina = (struct sockaddr_in*)&ifr.ifr_broadaddr;
+			dhcpv4_put(&reply, &cookie, DHCPV4_OPT_BROADCAST, 4, &ina->sin_addr);
+		}
+	}
+
+	if (!ioctl(sock, SIOCGIFMTU, &ifr)) {
+		uint16_t mtu = htons(ifr.ifr_mtu);
+		dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MTU, 2, &mtu);
+	}
+
+	if (iface->search) {
+		char b[256];
+		if (dn_expand(iface->search, iface->search + iface->search_len,
+				iface->search, b, sizeof(b)) > 0)
+			dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DOMAIN, strlen(b), b);
+	} else if (!res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
+		dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DOMAIN,
+				strlen(_res.dnsrch[0]), _res.dnsrch[0]);
+	}
+
+	dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER, 4, &ifaddr.sin_addr);
+
+
+
+	if (iface->dhcpv4_dns_cnt == 0)
+		dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER, 4, &ifaddr.sin_addr);
+	else
+		dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER,
+				4 * iface->dhcpv4_dns_cnt, iface->dhcpv4_dns);
+
+
+	dhcpv4_put(&reply, &cookie, DHCPV4_OPT_END, 0, NULL);
+
+	struct sockaddr_in dest = *((struct sockaddr_in*)addr);
+	if (req->giaddr.s_addr) {
+		dest.sin_addr = req->giaddr;
+		dest.sin_port = htons(DHCPV4_SERVER_PORT);
+	} else if (req->ciaddr.s_addr && req->ciaddr.s_addr != dest.sin_addr.s_addr) {
+		dest.sin_addr = req->ciaddr;
+		dest.sin_port = htons(DHCPV4_CLIENT_PORT);
+	} else if ((ntohs(req->flags) & DHCPV4_FLAG_BROADCAST) ||
+			req->hlen != reply.hlen) {
+		dest.sin_addr.s_addr = INADDR_BROADCAST;
+		dest.sin_port = htons(DHCPV4_CLIENT_PORT);
+	} else {
+		dest.sin_addr = reply.yiaddr;
+		dest.sin_port = htons(DHCPV4_CLIENT_PORT);
+
+		struct arpreq arp = {.arp_flags = ATF_COM};
+		memcpy(arp.arp_ha.sa_data, req->chaddr, 6);
+		memcpy(&arp.arp_pa, &dest, sizeof(arp.arp_pa));
+		memcpy(arp.arp_dev, iface->ifname, sizeof(arp.arp_dev));
+		ioctl(sock, SIOCSARP, &arp);
+	}
+
+	sendto(sock, &reply, sizeof(reply), MSG_DONTWAIT,
+			(struct sockaddr*)&dest, sizeof(dest));
+}
+
+
+static bool dhcpv4_assign(struct interface *iface,
+		struct dhcpv4_assignment *assign, uint32_t raddr)
+{
+	const unsigned tries = 10;
+	uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
+	uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
+	uint32_t count = end - start + 1;
+
+	// Seed RNG with checksum of DUID
+	uint32_t seed = 0;
+	for (size_t i = 0; i < sizeof(assign->hwaddr); ++i)
+		seed += assign->hwaddr[i];
+	srand(seed);
+
+	// Try to assign up to 100x
+	for (unsigned i = 0; i < tries; ++i) {
+		uint32_t try = (((uint32_t)rand()) % count) + start;
+		if (i == 0 && raddr >= start && raddr <= end)
+			try = raddr;
+		else if (i == tries - 1)
+			try = start;
+
+		if (list_empty(&iface->dhcpv4_assignments)) {
+			assign->addr = try;
+			list_add(&assign->head, &iface->dhcpv4_assignments);
+			return true;
+		}
+
+		struct dhcpv4_assignment *c;
+		list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
+			if (c->addr > try) {
+				assign->addr = try;
+				list_add_tail(&assign->head, &c->head);
+				return true;
+			} else if (c->addr == try) {
+				if (i < tries - 1)
+					break;
+				else
+					++try;
+			}
+		}
+	}
+
+	return false;
+}
+
+
+static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
+		enum dhcpv4_msg msg, const uint8_t *mac, struct in_addr reqaddr,
+		const char *hostname)
+{
+	struct dhcpv4_assignment *lease = NULL;
+	uint32_t raddr = ntohl(reqaddr.s_addr);
+	time_t now = odhcpd_time();
+
+	struct dhcpv4_assignment *c, *n, *a = NULL;
+	list_for_each_entry_safe(c, n, &iface->dhcpv4_assignments, head) {
+		if (c->addr == raddr && !memcmp(c->hwaddr, mac, 6)) {
+			a = c;
+			break;
+		} else if (c->valid_until < now) {
+			list_del(&c->head);
+			free(c);
+		}
+	}
+
+	bool update_state = false;
+	if (msg == DHCPV4_MSG_DISCOVER || msg == DHCPV4_MSG_REQUEST) {
+		bool assigned = !!a;
+		size_t hostlen = strlen(hostname) + 1;
+
+		if (!a && !iface->no_dynamic_dhcp) { // Create new binding
+			a = calloc(1, sizeof(*a) + hostlen);
+			memcpy(a->hwaddr, mac, sizeof(a->hwaddr));
+			memcpy(a->hostname, hostname, hostlen);
+
+			assigned = dhcpv4_assign(iface, a, raddr);
+		}
+
+		if (assigned && !a->hostname[0] && hostname) {
+			a = realloc(a, sizeof(*a) + hostlen);
+			memcpy(a->hostname, hostname, hostlen);
+
+			// Fixup list
+			a->head.next->prev = &a->head;
+			a->head.prev->next = &a->head;
+		}
+
+		// Was only a solicitation: mark binding for removal
+		if (assigned && a->valid_until < now) {
+			a->valid_until = (msg == DHCPV4_MSG_DISCOVER) ? 0 :
+					(now + iface->dhcpv4_leasetime);
+		} else if (!assigned && a) { // Cleanup failed assignment
+			free(a);
+			a = NULL;
+		}
+
+		if (assigned && a)
+			lease = a;
+	} else if (msg == DHCPV4_MSG_RELEASE) {
+		if (a) {
+			a->valid_until = 0;
+			update_state = true;
+		}
+	} else if (msg == DHCPV4_MSG_DECLINE) {
+		memset(a->hwaddr, 0, sizeof(a->hwaddr));
+		a->valid_until = now + 3600; // Block address for 1h
+		update_state = true;
+	}
+
+	if (update_state)
+		dhcpv6_write_statefile();
+
+	return lease;
+}
+