dhcpv6: add DHCPv4-over-DHCPv6 support

Add support for DHCPv4-over-DHCPv6 (DHCP 4o6) Transport (RFC 7341).

Signed-off-by: Mikael Magnusson <mikma@users.sourceforge.net>
Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>

4 files changed, 150 insertions, 4 deletions

diff --git a/src/dhcpv4.c b/src/dhcpv4.c
index 51236d2..25a4c77 100644
--- a/src/dhcpv4.c
+++ b/src/dhcpv4.c
@@ -588,10 +588,28 @@ static void dhcpv4_fr_stop(struct dhcp_assignment *a)
 	a->fr_timer.cb = NULL;
 }
 
+static int dhcpv4_send_reply(const void *buf, size_t len,
+			     const struct sockaddr *dest, socklen_t dest_len,
+			     void *opaque)
+{
+	int *sock = opaque;
+
+	return sendto(*sock, buf, len, MSG_DONTWAIT, dest, dest_len);
+}
+
 /* Handler for DHCPv4 messages */
 static void handle_dhcpv4(void *addr, void *data, size_t len,
 		struct interface *iface, _unused void *dest_addr)
 {
+	int sock = iface->dhcpv4_event.uloop.fd;
+
+	dhcpv4_handle_msg(addr, data, len, iface, dest_addr, dhcpv4_send_reply, &sock);
+}
+
+void dhcpv4_handle_msg(void *addr, void *data, size_t len,
+		struct interface *iface, _unused void *dest_addr,
+	        send_reply_cb_t send_reply, void *opaque)
+{
 	struct dhcpv4_message *req = data;
 
 	if (iface->dhcpv4 == MODE_DISABLED)
@@ -878,8 +896,8 @@ static void handle_dhcpv4(void *addr, void *data, size_t len,
 			syslog(LOG_ERR, "ioctl(SIOCSARP): %m");
 	}
 
-	if (sendto(sock, &reply, PACKET_SIZE(&reply, cookie), MSG_DONTWAIT,
-			(struct sockaddr*)&dest, sizeof(dest)) < 0)
+	if (send_reply(&reply, PACKET_SIZE(&reply, cookie),
+		       (struct sockaddr*)&dest, sizeof(dest), opaque) < 0)
 		syslog(LOG_ERR, "Failed to send %s to %s - %s: %m",
 			dhcpv4_msg_to_string(msg),
 			dest.sin_addr.s_addr == INADDR_BROADCAST ?
diff --git a/src/dhcpv6.c b/src/dhcpv6.c
index 7c6c7ab..cc068a3 100644
--- a/src/dhcpv6.c
+++ b/src/dhcpv6.c
@@ -25,7 +25,9 @@
 
 #include "odhcpd.h"
 #include "dhcpv6.h"
-
+#ifdef DHCPV4_SUPPORT
+#include "dhcpv4.h"
+#endif
 
 static void relay_client_request(struct sockaddr_in6 *source,
 		const void *data, size_t len, struct interface *iface);
@@ -175,6 +177,7 @@ enum {
 	IOV_CERID,
 	IOV_DHCPV6_RAW,
 	IOV_RELAY_MSG,
+	IOV_DHCPV4O6_SERVER,
 	IOV_TOTAL
 };
 
@@ -235,6 +238,68 @@ static void update_nested_message(uint8_t *data, size_t len, ssize_t pdiff)
 	}
 }
 
+#ifdef DHCPV4_SUPPORT
+
+struct dhcpv4_msg_data {
+	uint8_t *msg;
+	size_t maxsize;
+	ssize_t len;
+};
+
+static int send_reply(_unused const void *buf, size_t len,
+		      _unused const struct sockaddr *dest, _unused socklen_t dest_len,
+		      _unused void *opaque)
+{
+	struct dhcpv4_msg_data *reply = opaque;
+
+	if (len > reply->maxsize) {
+		syslog(LOG_ERR, "4o6: reply too large, %u > %u", len, reply->maxsize);
+		reply->len = -1;
+	} else {
+		memcpy(reply->msg, buf, len);
+		reply->len = len;
+	}
+
+	return reply->len;
+}
+
+static ssize_t dhcpv6_4o6_query(uint8_t *buf, size_t buflen,
+				struct interface *iface,
+				const struct sockaddr_in6 *addr,
+				const void *data, const uint8_t *end)
+{
+	const struct dhcpv6_client_header *hdr = data;
+	uint16_t otype, olen, msgv4_len = 0;
+	uint8_t *msgv4_data = NULL;
+	uint8_t *start = (uint8_t *)&hdr[1], *odata;
+	struct sockaddr_in addrv4;
+	struct dhcpv4_msg_data reply = { .msg = buf, .maxsize = buflen, .len = -1 };
+
+	dhcpv6_for_each_option(start, end, otype, olen, odata) {
+		if (otype == DHCPV6_OPT_DHCPV4_MSG) {
+			msgv4_data = odata;
+			msgv4_len = olen;
+		}
+	}
+
+	if (!msgv4_data || msgv4_len == 0) {
+		syslog(LOG_ERR, "4o6: missing DHCPv4 message option (%d)", DHCPV6_OPT_DHCPV4_MSG);
+		return -1;
+	}
+
+	// Dummy IPv4 address
+	memset(&addrv4, 0, sizeof(addrv4));
+	addrv4.sin_family = AF_INET;
+	addrv4.sin_addr.s_addr = INADDR_ANY;
+	addrv4.sin_port = htons(DHCPV4_CLIENT_PORT);
+
+	dhcpv4_handle_msg(&addrv4, msgv4_data, msgv4_len,
+			  iface, NULL, send_reply, &reply);
+
+	return reply.len;
+}
+#endif	/* DHCPV4_SUPPORT */
+
 /* Simple DHCPv6-server for information requests */
 static void handle_client_request(void *addr, void *data, size_t len,
 		struct interface *iface, void *dest_addr)
@@ -332,6 +397,11 @@ static void handle_client_request(void *addr, void *data, size_t len,
 	} search = {htons(DHCPV6_OPT_DNS_DOMAIN), htons(search_len)};
 
 
+	struct __attribute__((packed)) {
+		uint16_t type;
+		uint16_t len;
+	} dhcpv4o6_server = {htons(DHCPV6_OPT_4O6_SERVER), 0};
+
 	struct dhcpv6_cer_id cerid = {
 #ifdef EXT_CER_ID
 		.type = htons(EXT_CER_ID),
@@ -354,7 +424,8 @@ static void handle_client_request(void *addr, void *data, size_t len,
 		[IOV_PDBUF] = {pdbuf, 0},
 		[IOV_CERID] = {&cerid, 0},
 		[IOV_DHCPV6_RAW] = {iface->dhcpv6_raw, iface->dhcpv6_raw_len},
-		[IOV_RELAY_MSG] = {NULL, 0}
+		[IOV_RELAY_MSG] = {NULL, 0},
+		[IOV_DHCPV4O6_SERVER] = {&dhcpv4o6_server, 0},
 	};
 
 	if (hdr->msg_type == DHCPV6_MSG_RELAY_FORW)
@@ -370,11 +441,18 @@ static void handle_client_request(void *addr, void *data, size_t len,
 	case DHCPV6_MSG_DECLINE:
 	case DHCPV6_MSG_INFORMATION_REQUEST:
 	case DHCPV6_MSG_RELAY_FORW:
+#ifdef DHCPV4_SUPPORT
+	case DHCPV6_MSG_DHCPV4_QUERY:
+#endif
 		break; /* Valid message types for clients */
 	case DHCPV6_MSG_ADVERTISE:
 	case DHCPV6_MSG_REPLY:
 	case DHCPV6_MSG_RECONFIGURE:
 	case DHCPV6_MSG_RELAY_REPL:
+	case DHCPV6_MSG_DHCPV4_RESPONSE:
+#ifndef DHCPV4_SUPPORT
+	case DHCPV6_MSG_DHCPV4_QUERY:
+#endif
 	default:
 		return; /* Invalid message types for clients */
 	}
@@ -424,6 +502,20 @@ static void handle_client_request(void *addr, void *data, size_t len,
 		} else if (otype == DHCPV6_OPT_RAPID_COMMIT && hdr->msg_type == DHCPV6_MSG_SOLICIT) {
 			iov[IOV_RAPID_COMMIT].iov_len = sizeof(rapid_commit);
 			o_rapid_commit = true;
+		} else if (otype == DHCPV6_OPT_ORO) {
+			for (int i=0; i < olen/2; i++) {
+				uint16_t option = ntohs(((uint16_t *)odata)[i]);
+				switch (option) {
+#ifdef DHCPV4_SUPPORT
+				case DHCPV6_OPT_4O6_SERVER:
+					if (iface->dhcpv4)
+						iov[IOV_DHCPV4O6_SERVER].iov_len = sizeof(dhcpv4o6_server);
+					break;
+#endif /* DHCPV4_SUPPORT */
+				default:
+					break;
+				}
+			}
 		}
 	}
 
@@ -450,6 +542,30 @@ static void handle_client_request(void *addr, void *data, size_t len,
 		maxrt.type = htons(DHCPV6_OPT_INF_MAX_RT);
 	}
 
+#ifdef DHCPV4_SUPPORT
+	if (hdr->msg_type == DHCPV6_MSG_DHCPV4_QUERY) {
+		struct _packed dhcpv4_msg_data {
+			uint16_t type;
+			uint16_t len;
+			uint8_t msg[1];
+		} *msg_opt = (struct dhcpv4_msg_data*)pdbuf;
+		ssize_t msglen;
+
+		memset(pdbuf, 0, sizeof(pdbuf));
+
+		msglen = dhcpv6_4o6_query(msg_opt->msg, sizeof(pdbuf) - sizeof(*msg_opt) + 1,
+						iface, addr, (const void *)hdr, opts_end);
+		if (msglen <= 0) {
+			syslog(LOG_ERR, "4o6: query failed");
+			return;
+		}
+
+		msg_opt->type = htons(DHCPV6_OPT_DHCPV4_MSG);
+		msg_opt->len = htons(msglen);
+		iov[IOV_PDBUF].iov_len = sizeof(*msg_opt) - 1 + msglen;
+		dest.msg_type = DHCPV6_MSG_DHCPV4_RESPONSE;
+	} else
+#endif	/* DHCPV4_SUPPORT */
 	if (hdr->msg_type != DHCPV6_MSG_INFORMATION_REQUEST) {
 		ssize_t ialen = dhcpv6_ia_handle_IAs(pdbuf, sizeof(pdbuf), iface, addr, (const void *)hdr, opts_end);
 
@@ -464,6 +580,7 @@ static void handle_client_request(void *addr, void *data, size_t len,
 				      iov[IOV_RAPID_COMMIT].iov_len + iov[IOV_DNS].iov_len +
 				      iov[IOV_DNS_ADDR].iov_len + iov[IOV_SEARCH].iov_len +
 				      iov[IOV_SEARCH_DOMAIN].iov_len + iov[IOV_PDBUF].iov_len +
+				      iov[IOV_DHCPV4O6_SERVER].iov_len +
 				      iov[IOV_CERID].iov_len + iov[IOV_DHCPV6_RAW].iov_len -
 				      (4 + opts_end - opts));
 
diff --git a/src/dhcpv6.h b/src/dhcpv6.h
index aaf919c..c96dc0d 100644
--- a/src/dhcpv6.h
+++ b/src/dhcpv6.h
@@ -35,6 +35,8 @@
 #define DHCPV6_MSG_INFORMATION_REQUEST 11
 #define DHCPV6_MSG_RELAY_FORW 12
 #define DHCPV6_MSG_RELAY_REPL 13
+#define DHCPV6_MSG_DHCPV4_QUERY 20
+#define DHCPV6_MSG_DHCPV4_RESPONSE 21
 
 #define DHCPV6_OPT_CLIENTID 1
 #define DHCPV6_OPT_SERVERID 2
@@ -57,6 +59,8 @@
 #define DHCPV6_OPT_FQDN 39
 #define DHCPV6_OPT_SOL_MAX_RT 82
 #define DHCPV6_OPT_INF_MAX_RT 83
+#define DHCPV6_OPT_DHCPV4_MSG 87
+#define DHCPV6_OPT_4O6_SERVER 88
 
 #define DHCPV6_DUID_VENDOR 2
 
diff --git a/src/odhcpd.h b/src/odhcpd.h
index 09013c4..787be1f 100644
--- a/src/odhcpd.h
+++ b/src/odhcpd.h
@@ -54,6 +54,10 @@ struct odhcpd_event {
 	void (*recv_msgs)(struct odhcpd_event *e);
 };
 
+typedef	int (*send_reply_cb_t)(const void *buf, size_t len,
+			       const struct sockaddr *dest, socklen_t dest_len,
+			       void *opaque);
+
 typedef void (*dhcpv6_binding_cb_handler_t)(struct in6_addr *addr, int prefix,
 					    uint32_t pref, uint32_t valid,
 					    void *arg);
@@ -411,6 +415,9 @@ int ndp_init(void);
 int dhcpv4_init(void);
 
 int dhcpv4_setup_interface(struct interface *iface, bool enable);
+void dhcpv4_handle_msg(void *addr, void *data, size_t len,
+		       struct interface *iface, _unused void *dest_addr,
+		       send_reply_cb_t send_reply, void *opaque);
 #endif
 int router_setup_interface(struct interface *iface, bool enable);
 int dhcpv6_setup_interface(struct interface *iface, bool enable);