treewide: switch to C-code style comments
[oweals/odhcpd.git] / src / dhcpv6.c
index 55b9ea9208f8aee993bdde236a8c34b440cd3583..4e7d0d014b29a7b5b3454aaa00aba3525b6d5b2b 100644 (file)
 #include <stddef.h>
 #include <resolv.h>
 #include <sys/timerfd.h>
+#include <arpa/inet.h>
 
 #include "odhcpd.h"
 #include "dhcpv6.h"
 
-static const char *excluded_class = "HOMENET";
-
 
 static void relay_client_request(struct sockaddr_in6 *source,
                const void *data, size_t len, struct interface *iface);
 static void relay_server_response(uint8_t *data, size_t len);
 
 static void handle_dhcpv6(void *addr, void *data, size_t len,
-               struct interface *iface);
+               struct interface *iface, void *dest);
 static void handle_client_request(void *addr, void *data, size_t len,
-               struct interface *iface);
-
+               struct interface *iface, void *dest_addr);
 
 
-// Create socket and register events
-int init_dhcpv6(void)
+/* Create socket and register events */
+int dhcpv6_init(void)
 {
        dhcpv6_ia_init();
        return 0;
 }
 
-
-int setup_dhcpv6_interface(struct interface *iface, bool enable)
+int dhcpv6_setup_interface(struct interface *iface, bool enable)
 {
+       int ret = 0;
+
        if (iface->dhcpv6_event.uloop.fd > 0) {
                uloop_fd_delete(&iface->dhcpv6_event.uloop);
                close(iface->dhcpv6_event.uloop.fd);
                iface->dhcpv6_event.uloop.fd = -1;
        }
 
-       // Configure multicast settings
-       if (enable && iface->dhcpv6 && !iface->master) {
-               int sock = socket(AF_INET6, SOCK_DGRAM | SOCK_CLOEXEC, IPPROTO_UDP);
-               if (sock < 0) {
-                       syslog(LOG_ERR, "Failed to create DHCPv6 server socket: %s",
-                                       strerror(errno));
-                       return -1;
+       /* Configure multicast settings */
+       if (enable && iface->dhcpv6) {
+               struct sockaddr_in6 bind_addr = {AF_INET6, htons(DHCPV6_SERVER_PORT),
+                                       0, IN6ADDR_ANY_INIT, 0};
+               struct ipv6_mreq mreq;
+               int val = 1;
+
+               iface->dhcpv6_event.uloop.fd = socket(AF_INET6, SOCK_DGRAM | SOCK_CLOEXEC, IPPROTO_UDP);
+               if (iface->dhcpv6_event.uloop.fd < 0) {
+                       syslog(LOG_ERR, "socket(AF_INET6): %m");
+                       ret = -1;
+                       goto out;
                }
 
-               // Basic IPv6 configuration
-               setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, iface->ifname, strlen(iface->ifname));
+               /* Basic IPv6 configuration */
+               if (setsockopt(iface->dhcpv6_event.uloop.fd, SOL_SOCKET, SO_BINDTODEVICE,
+                                       iface->ifname, strlen(iface->ifname)) < 0) {
+                       syslog(LOG_ERR, "setsockopt(SO_BINDTODEVICE): %m");
+                       ret = -1;
+                       goto out;
+               }
 
-               int val = 1;
-               setsockopt(sock, IPPROTO_IPV6, IPV6_V6ONLY, &val, sizeof(val));
-               setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val));
-               setsockopt(sock, IPPROTO_IPV6, IPV6_RECVPKTINFO, &val, sizeof(val));
+               if (setsockopt(iface->dhcpv6_event.uloop.fd, IPPROTO_IPV6, IPV6_V6ONLY,
+                                       &val, sizeof(val)) < 0) {
+                       syslog(LOG_ERR, "setsockopt(IPV6_V6ONLY): %m");
+                       ret = -1;
+                       goto out;
+               }
+
+               if (setsockopt(iface->dhcpv6_event.uloop.fd, SOL_SOCKET, SO_REUSEADDR,
+                                       &val, sizeof(val)) < 0) {
+                       syslog(LOG_ERR, "setsockopt(SO_REUSEADDR): %m");
+                       ret = -1;
+                       goto out;
+               }
+
+               if (setsockopt(iface->dhcpv6_event.uloop.fd, IPPROTO_IPV6, IPV6_RECVPKTINFO,
+                                       &val, sizeof(val)) < 0) {
+                       syslog(LOG_ERR, "setsockopt(IPV6_RECVPKTINFO): %m");
+                       ret = -1;
+                       goto out;
+               }
 
                val = DHCPV6_HOP_COUNT_LIMIT;
-               setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
+               if (setsockopt(iface->dhcpv6_event.uloop.fd, IPPROTO_IPV6, IPV6_MULTICAST_HOPS,
+                                       &val, sizeof(val)) < 0) {
+                       syslog(LOG_ERR, "setsockopt(IPV6_MULTICAST_HOPS): %m");
+                       ret = -1;
+                       goto out;
+               }
 
                val = 0;
-               setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, &val, sizeof(val));
+               if (setsockopt(iface->dhcpv6_event.uloop.fd, IPPROTO_IPV6, IPV6_MULTICAST_LOOP,
+                                       &val, sizeof(val)) < 0) {
+                       syslog(LOG_ERR, "setsockopt(IPV6_MULTICAST_LOOP): %m");
+                       ret = -1;
+                       goto out;
+               }
 
-               struct sockaddr_in6 bind_addr = {AF_INET6, htons(DHCPV6_SERVER_PORT),
-                                       0, IN6ADDR_ANY_INIT, 0};
+               if (bind(iface->dhcpv6_event.uloop.fd, (struct sockaddr*)&bind_addr,
+                                       sizeof(bind_addr)) < 0) {
+                       syslog(LOG_ERR, "bind(): %m");
+                       ret = -1;
+                       goto out;
+               }
+
+               memset(&mreq, 0, sizeof(mreq));
+               inet_pton(AF_INET6, ALL_DHCPV6_RELAYS, &mreq.ipv6mr_multiaddr);
+               mreq.ipv6mr_interface = iface->ifindex;
 
-               if (bind(sock, (struct sockaddr*)&bind_addr, sizeof(bind_addr))) {
-                       syslog(LOG_ERR, "Failed to open DHCPv6 server socket: %s",
-                                       strerror(errno));
-                       return -1;
+               if (setsockopt(iface->dhcpv6_event.uloop.fd, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP,
+                                       &mreq, sizeof(mreq)) < 0) {
+                       syslog(LOG_ERR, "setsockopt(IPV6_ADD_MEMBERSHIP): %m");
+                       ret = -1;
+                       goto out;
                }
 
-               struct ipv6_mreq relay = {ALL_DHCPV6_RELAYS, iface->ifindex};
-               struct ipv6_mreq server = {ALL_DHCPV6_SERVERS, iface->ifindex};
-               setsockopt(sock, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, &relay, sizeof(relay));
+               if (iface->dhcpv6 == MODE_SERVER) {
+                       memset(&mreq, 0, sizeof(mreq));
+                       inet_pton(AF_INET6, ALL_DHCPV6_SERVERS, &mreq.ipv6mr_multiaddr);
+                       mreq.ipv6mr_interface = iface->ifindex;
 
-               if (iface->dhcpv6 == RELAYD_SERVER)
-                       setsockopt(sock, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, &server, sizeof(server));
+                       if (setsockopt(iface->dhcpv6_event.uloop.fd, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP,
+                                               &mreq, sizeof(mreq)) < 0) {
+                               syslog(LOG_ERR, "setsockopt(IPV6_ADD_MEMBERSHIP): %m");
+                               ret = -1;
+                               goto out;
+                       }
+               }
 
-               iface->dhcpv6_event.uloop.fd = sock;
                iface->dhcpv6_event.handle_dgram = handle_dhcpv6;
                odhcpd_register(&iface->dhcpv6_event);
        }
 
-       return setup_dhcpv6_ia_interface(iface, enable);
+       ret = dhcpv6_setup_ia_interface(iface, enable);
+
+out:
+       if (ret < 0 && iface->dhcpv6_event.uloop.fd > 0) {
+               close(iface->dhcpv6_event.uloop.fd);
+               iface->dhcpv6_event.uloop.fd = -1;
+       }
+
+       return ret;
 }
 
+enum {
+       IOV_NESTED = 0,
+       IOV_DEST,
+       IOV_MAXRT,
+#define IOV_STAT IOV_MAXRT
+       IOV_DNS,
+       IOV_DNS_ADDR,
+       IOV_SEARCH,
+       IOV_SEARCH_DOMAIN,
+       IOV_PDBUF,
+#define        IOV_REFRESH IOV_PDBUF
+       IOV_CERID,
+       IOV_DHCPV6_RAW,
+       IOV_RELAY_MSG,
+       IOV_TOTAL
+};
 
 static void handle_nested_message(uint8_t *data, size_t len,
-               uint8_t **opts, uint8_t **end, struct iovec iov[9])
+               uint8_t **opts, uint8_t **end, struct iovec iov[IOV_TOTAL - 1])
 {
        struct dhcpv6_relay_header *hdr = (struct dhcpv6_relay_header*)data;
-       if (iov[0].iov_base == NULL) {
-               iov[0].iov_base = data;
-               iov[0].iov_len = len;
+       if (iov[IOV_NESTED].iov_base == NULL) {
+               iov[IOV_NESTED].iov_base = data;
+               iov[IOV_NESTED].iov_len = len;
        }
 
        if (len < sizeof(struct dhcpv6_client_header))
                return;
 
        if (hdr->msg_type != DHCPV6_MSG_RELAY_FORW) {
-               iov[0].iov_len = data - (uint8_t*)iov[0].iov_base;
+               iov[IOV_NESTED].iov_len = data - (uint8_t*)iov[IOV_NESTED].iov_base;
                struct dhcpv6_client_header *hdr = (void*)data;
                *opts = (uint8_t*)&hdr[1];
                *end = data + len;
@@ -124,9 +197,9 @@ static void handle_nested_message(uint8_t *data, size_t len,
        uint8_t *odata;
        dhcpv6_for_each_option(hdr->options, data + len, otype, olen, odata) {
                if (otype == DHCPV6_OPT_RELAY_MSG) {
-                       iov[8].iov_base = odata + olen;
-                       iov[8].iov_len = (((uint8_t*)iov[0].iov_base) + iov[0].iov_len)
-                                       - (odata + olen);
+                       iov[IOV_RELAY_MSG].iov_base = odata + olen;
+                       iov[IOV_RELAY_MSG].iov_len = (((uint8_t*)iov[IOV_NESTED].iov_base) + 
+                                       iov[IOV_NESTED].iov_len) - (odata + olen);
                        handle_nested_message(odata, olen, opts, end, iov);
                        return;
                }
@@ -155,18 +228,18 @@ static void update_nested_message(uint8_t *data, size_t len, ssize_t pdiff)
        }
 }
 
-
-// Simple DHCPv6-server for information requests
+/* Simple DHCPv6-server for information requests */
 static void handle_client_request(void *addr, void *data, size_t len,
-               struct interface *iface)
+               struct interface *iface, void *dest_addr)
 {
        struct dhcpv6_client_header *hdr = data;
+
        if (len < sizeof(*hdr))
                return;
 
        syslog(LOG_NOTICE, "Got DHCPv6 request");
 
-       // Construct reply message
+       /* Construct reply message */
        struct __attribute__((packed)) {
                uint8_t msg_type;
                uint8_t tr_id[3];
@@ -175,9 +248,6 @@ static void handle_client_request(void *addr, void *data, size_t len,
                uint16_t duid_type;
                uint16_t hardware_type;
                uint8_t mac[6];
-               uint16_t solmaxrt_type;
-               uint16_t solmaxrt_length;
-               uint32_t solmaxrt_value;
                uint16_t clientid_type;
                uint16_t clientid_length;
                uint8_t clientid_buf[130];
@@ -187,20 +257,24 @@ static void handle_client_request(void *addr, void *data, size_t len,
                .serverid_length = htons(10),
                .duid_type = htons(3),
                .hardware_type = htons(1),
-               .solmaxrt_type = htons(DHCPV6_OPT_SOL_MAX_RT),
-               .solmaxrt_length = htons(4),
-               .solmaxrt_value = htonl(60),
                .clientid_type = htons(DHCPV6_OPT_CLIENTID),
                .clientid_buf = {0}
        };
        odhcpd_get_mac(iface, dest.mac);
 
+       struct __attribute__((packed)) {
+               uint16_t type;
+               uint16_t len;
+               uint32_t value;
+       } maxrt = {htons(DHCPV6_OPT_SOL_MAX_RT), htons(sizeof(maxrt) - 4),
+                       htonl(60)};
+
        struct __attribute__((packed)) {
                uint16_t type;
                uint16_t len;
                uint16_t value;
        } stat = {htons(DHCPV6_OPT_STATUS), htons(sizeof(stat) - 4),
-                       htons(DHCPV6_STATUS_NOADDRSAVAIL)};
+                       htons(DHCPV6_STATUS_USEMULTICAST)};
 
        struct __attribute__((packed)) {
                uint16_t type;
@@ -209,23 +283,23 @@ static void handle_client_request(void *addr, void *data, size_t len,
        } refresh = {htons(DHCPV6_OPT_INFO_REFRESH), htons(sizeof(uint32_t)),
                        htonl(600)};
 
-       struct odhcpd_ipaddr ipaddr;
-       struct in6_addr *dns_addr = iface->dns;
+       struct in6_addr dns_addr, *dns_addr_ptr = iface->dns;
        size_t dns_cnt = iface->dns_cnt;
 
-       if (dns_cnt == 0 && odhcpd_get_interface_addresses(iface->ifindex, &ipaddr, 1) == 1) {
-               dns_addr = &ipaddr.addr;
+       if ((dns_cnt == 0) &&
+               !odhcpd_get_interface_dns_addr(iface, &dns_addr)) {
+               dns_addr_ptr = &dns_addr;
                dns_cnt = 1;
        }
 
        struct {
                uint16_t type;
                uint16_t len;
-       } dns = {htons(DHCPV6_OPT_DNS_SERVERS), htons(dns_cnt * sizeof(*dns_addr))};
+       } dns = {htons(DHCPV6_OPT_DNS_SERVERS), htons(dns_cnt * sizeof(*dns_addr_ptr))};
 
 
 
-       // DNS Search options
+       /* DNS Search options */
        uint8_t search_buf[256], *search_domain = iface->search;
        size_t search_len = iface->search_len;
 
@@ -254,15 +328,19 @@ static void handle_client_request(void *addr, void *data, size_t len,
 
 
        uint8_t pdbuf[512];
-       struct iovec iov[] = {{NULL, 0},
-                       {&dest, (uint8_t*)&dest.clientid_type - (uint8_t*)&dest},
-                       {&dns, (dns_cnt) ? sizeof(dns) : 0},
-                       {dns_addr, dns_cnt * sizeof(*dns_addr)},
-                       {&search, (search_len) ? sizeof(search) : 0},
-                       {search_domain, search_len},
-                       {pdbuf, 0},
-                       {&cerid, 0},
-                       {NULL, 0}};
+       struct iovec iov[IOV_TOTAL] = {
+               [IOV_NESTED] = {NULL, 0},
+               [IOV_DEST] = {&dest, (uint8_t*)&dest.clientid_type - (uint8_t*)&dest},
+               [IOV_MAXRT] = {&maxrt, sizeof(maxrt)},
+               [IOV_DNS] = {&dns, (dns_cnt) ? sizeof(dns) : 0},
+               [IOV_DNS_ADDR] = {dns_addr_ptr, dns_cnt * sizeof(*dns_addr_ptr)},
+               [IOV_SEARCH] = {&search, (search_len) ? sizeof(search) : 0},
+               [IOV_SEARCH_DOMAIN] = {search_domain, search_len},
+               [IOV_PDBUF] = {pdbuf, 0},
+               [IOV_CERID] = {&cerid, 0},
+               [IOV_DHCPV6_RAW] = {iface->dhcpv6_raw, iface->dhcpv6_raw_len},
+               [IOV_RELAY_MSG] = {NULL, 0}
+       };
 
        uint8_t *opts = (uint8_t*)&hdr[1], *opts_end = (uint8_t*)data + len;
        if (hdr->msg_type == DHCPV6_MSG_RELAY_FORW)
@@ -273,73 +351,97 @@ static void handle_client_request(void *addr, void *data, size_t len,
        if (opts[-4] == DHCPV6_MSG_ADVERTISE || opts[-4] == DHCPV6_MSG_REPLY || opts[-4] == DHCPV6_MSG_RELAY_REPL)
                return;
 
+       if (!IN6_IS_ADDR_MULTICAST((struct in6_addr *)dest_addr) && iov[IOV_NESTED].iov_len == 0 &&
+               (opts[-4] == DHCPV6_MSG_SOLICIT || opts[-4] == DHCPV6_MSG_CONFIRM ||
+                opts[-4] == DHCPV6_MSG_REBIND || opts[-4] == DHCPV6_MSG_INFORMATION_REQUEST))
+               return;
+
        if (opts[-4] == DHCPV6_MSG_SOLICIT) {
                dest.msg_type = DHCPV6_MSG_ADVERTISE;
        } else if (opts[-4] == DHCPV6_MSG_INFORMATION_REQUEST) {
-               iov[6].iov_base = &refresh;
-               iov[6].iov_len = sizeof(refresh);
+               iov[IOV_REFRESH].iov_base = &refresh;
+               iov[IOV_REFRESH].iov_len = sizeof(refresh);
+
+               /* Return inf max rt option in reply to information request */
+               maxrt.type = htons(DHCPV6_OPT_INF_MAX_RT);
        }
 
-       // Go through options and find what we need
+       /* Go through options and find what we need */
        uint16_t otype, olen;
        uint8_t *odata;
        dhcpv6_for_each_option(opts, opts_end, otype, olen, odata) {
                if (otype == DHCPV6_OPT_CLIENTID && olen <= 130) {
                        dest.clientid_length = htons(olen);
                        memcpy(dest.clientid_buf, odata, olen);
-                       iov[1].iov_len += 4 + olen;
+                       iov[IOV_DEST].iov_len += 4 + olen;
                } else if (otype == DHCPV6_OPT_SERVERID) {
                        if (olen != ntohs(dest.serverid_length) ||
                                        memcmp(odata, &dest.duid_type, olen))
-                               return; // Not for us
-               } else if (otype == DHCPV6_OPT_USER_CLASS) {
+                               return; /* Not for us */
+               } else if (iface->filter_class && otype == DHCPV6_OPT_USER_CLASS) {
                        uint8_t *c = odata, *cend = &odata[olen];
                        for (; &c[2] <= cend && &c[2 + (c[0] << 8) + c[1]] <= cend; c = &c[2 + (c[0] << 8) + c[1]]) {
-                               size_t elen = strlen(excluded_class);
-                               if (((((size_t)c[0]) << 8) | c[1]) == elen && !memcmp(&c[2], excluded_class, elen))
-                                       return; // Ignore from homenet
+                               size_t elen = strlen(iface->filter_class);
+                               if (((((size_t)c[0]) << 8) | c[1]) == elen && !memcmp(&c[2], iface->filter_class, elen))
+                                       return; /* Ignore from homenet */
                        }
                } else if (otype == DHCPV6_OPT_IA_PD) {
 #ifdef EXT_CER_ID
-                       iov[7].iov_len = sizeof(cerid);
+                       iov[IOV_CERID].iov_len = sizeof(cerid);
 
                        if (IN6_IS_ADDR_UNSPECIFIED(&cerid.addr)) {
-                               struct odhcpd_ipaddr addrs[32];
-                               ssize_t len = odhcpd_get_interface_addresses(0, addrs,
-                                               sizeof(addrs) / sizeof(*addrs));
+                               struct odhcpd_ipaddr *addrs;
+                               ssize_t len = netlink_get_interface_addrs(0, true, &addrs);
 
                                for (ssize_t i = 0; i < len; ++i)
                                        if (IN6_IS_ADDR_UNSPECIFIED(&cerid.addr)
                                                        || memcmp(&addrs[i].addr, &cerid.addr, sizeof(cerid.addr)) < 0)
-                                               cerid.addr = addrs[i].addr;
+                                               cerid.addr = addrs[i].addr.in6;
+
+                               free(addrs);
                        }
 #endif
                }
        }
 
+       if (!IN6_IS_ADDR_MULTICAST((struct in6_addr *)dest_addr) && iov[IOV_NESTED].iov_len == 0 &&
+               (opts[-4] == DHCPV6_MSG_REQUEST || opts[-4] == DHCPV6_MSG_RENEW ||
+                opts[-4] == DHCPV6_MSG_RELEASE || opts[-4] == DHCPV6_MSG_DECLINE)) {
+               iov[IOV_STAT].iov_base = &stat;
+               iov[IOV_STAT].iov_len = sizeof(stat);
+
+               for (ssize_t i = IOV_STAT + 1; i < IOV_TOTAL; ++i)
+                       iov[i].iov_len = 0;
+
+               odhcpd_send(iface->dhcpv6_event.uloop.fd, addr, iov, ARRAY_SIZE(iov), iface);
+               return;
+       }
+
        if (opts[-4] != DHCPV6_MSG_INFORMATION_REQUEST) {
                ssize_t ialen = dhcpv6_handle_ia(pdbuf, sizeof(pdbuf), iface, addr, &opts[-4], opts_end);
-               iov[6].iov_len = ialen;
+               iov[IOV_PDBUF].iov_len = ialen;
                if (ialen < 0 || (ialen == 0 && (opts[-4] == DHCPV6_MSG_REBIND || opts[-4] == DHCPV6_MSG_CONFIRM)))
                        return;
        }
 
-       if (iov[0].iov_len > 0) // Update length
-               update_nested_message(data, len, iov[1].iov_len + iov[2].iov_len +
-                               iov[3].iov_len + iov[4].iov_len + iov[5].iov_len +
-                               iov[6].iov_len + iov[7].iov_len - (4 + opts_end - opts));
+       if (iov[IOV_NESTED].iov_len > 0) /* Update length */
+               update_nested_message(data, len, iov[IOV_DEST].iov_len + iov[IOV_MAXRT].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_CERID].iov_len +
+                               iov[IOV_DHCPV6_RAW].iov_len - (4 + opts_end - opts));
 
        odhcpd_send(iface->dhcpv6_event.uloop.fd, addr, iov, ARRAY_SIZE(iov), iface);
 }
 
 
-// Central DHCPv6-relay handler
+/* Central DHCPv6-relay handler */
 static void handle_dhcpv6(void *addr, void *data, size_t len,
-               struct interface *iface)
+               struct interface *iface, void *dest_addr)
 {
-       if (iface->dhcpv6 == RELAYD_SERVER) {
-               handle_client_request(addr, data, len, iface);
-       } else if (iface->dhcpv6 == RELAYD_RELAY) {
+       if (iface->dhcpv6 == MODE_SERVER) {
+               handle_client_request(addr, data, len, iface, dest_addr);
+       } else if (iface->dhcpv6 == MODE_RELAY) {
                if (iface->master)
                        relay_server_response(data, len);
                else
@@ -348,10 +450,10 @@ static void handle_dhcpv6(void *addr, void *data, size_t len,
 }
 
 
-// Relay server response (regular relay server handling)
+/* Relay server response (regular relay server handling) */
 static void relay_server_response(uint8_t *data, size_t len)
 {
-       // Information we need to gather
+       /* Information we need to gather */
        uint8_t *payload_data = NULL;
        size_t payload_len = 0;
        int32_t ifaceidx = 0;
@@ -363,7 +465,7 @@ static void relay_server_response(uint8_t *data, size_t len)
        int otype, olen;
        uint8_t *odata, *end = data + len;
 
-       // Relay DHCPv6 reply from server to client
+       /* Relay DHCPv6 reply from server to client */
        struct dhcpv6_relay_header *h = (void*)data;
        if (len < sizeof(*h) || h->msg_type != DHCPV6_MSG_RELAY_REPL)
                return;
@@ -371,7 +473,7 @@ static void relay_server_response(uint8_t *data, size_t len)
        memcpy(&target.sin6_addr, &h->peer_address,
                        sizeof(struct in6_addr));
 
-       // Go through options and find what we need
+       /* Go through options and find what we need */
        dhcpv6_for_each_option(h->options, end, otype, olen, odata) {
                if (otype == DHCPV6_OPT_INTERFACE_ID
                                && olen == sizeof(ifaceidx)) {
@@ -382,7 +484,7 @@ static void relay_server_response(uint8_t *data, size_t len)
                }
        }
 
-       // Invalid interface-id or basic payload
+       /* Invalid interface-id or basic payload */
        struct interface *iface = odhcpd_get_interface_by_index(ifaceidx);
        if (!iface || iface->master || !payload_data || payload_len < 4)
                return;
@@ -391,10 +493,10 @@ static void relay_server_response(uint8_t *data, size_t len)
        struct in6_addr *dns_ptr = NULL;
        size_t dns_count = 0;
 
-       // If the payload is relay-reply we have to send to the server port
+       /* If the payload is relay-reply we have to send to the server port */
        if (payload_data[0] == DHCPV6_MSG_RELAY_REPL) {
                target.sin6_port = htons(DHCPV6_SERVER_PORT);
-       } else { // Go through the payload data
+       } else { /* Go through the payload data */
                struct dhcpv6_client_header *h = (void*)payload_data;
                end = payload_data + payload_len;
 
@@ -408,24 +510,24 @@ static void relay_server_response(uint8_t *data, size_t len)
                }
        }
 
-       // Rewrite DNS servers if requested
+       /* Rewrite DNS servers if requested */
        if (iface->always_rewrite_dns && dns_ptr && dns_count > 0) {
                if (is_authenticated)
-                       return; // Impossible to rewrite
+                       return; /* Impossible to rewrite */
 
-               struct odhcpd_ipaddr ip;
                const struct in6_addr *rewrite = iface->dns;
+               struct in6_addr addr;
                size_t rewrite_cnt = iface->dns_cnt;
 
                if (rewrite_cnt == 0) {
-                       if (odhcpd_get_interface_addresses(iface->ifindex, &ip, 1) < 1)
+                       if (odhcpd_get_interface_dns_addr(iface, &addr))
                                return; // Unable to get interface address
 
-                       rewrite = &ip.addr;
+                       rewrite = &addr;
                        rewrite_cnt = 1;
                }
 
-               // Copy over any other addresses
+               /* Copy over any other addresses */
                for (size_t i = 0; i < dns_count; ++i) {
                        size_t j = (i < rewrite_cnt) ? i : rewrite_cnt - 1;
                        memcpy(&dns_ptr[i], &rewrite[j], sizeof(*rewrite));
@@ -436,23 +538,45 @@ static void relay_server_response(uint8_t *data, size_t len)
        odhcpd_send(iface->dhcpv6_event.uloop.fd, &target, &iov, 1, iface);
 }
 
+static struct odhcpd_ipaddr *relay_link_address(struct interface *iface)
+{
+       struct odhcpd_ipaddr *addr = NULL;
+       time_t now = odhcpd_time();
+
+       for (size_t i = 0; i < iface->addr6_len; i++) {
+               if (iface->addr6[i].valid <= (uint32_t)now)
+                       continue;
+
+               if (iface->addr6[i].preferred > (uint32_t)now) {
+                       addr = &iface->addr6[i];
+                       break;
+               }
+
+               if (!addr || (iface->addr6[i].valid > addr->valid))
+                       addr = &iface->addr6[i];
+       }
+
+       return addr;
+}
 
-// Relay client request (regular DHCPv6-relay)
+/* Relay client request (regular DHCPv6-relay) */
 static void relay_client_request(struct sockaddr_in6 *source,
                const void *data, size_t len, struct interface *iface)
 {
        struct interface *master = odhcpd_get_master_interface();
        const struct dhcpv6_relay_header *h = data;
-       if (!master || master->dhcpv6 != RELAYD_RELAY ||
+       struct sockaddr_in6 s;
+
+       if (!master || master->dhcpv6 != MODE_RELAY ||
                        h->msg_type == DHCPV6_MSG_RELAY_REPL ||
                        h->msg_type == DHCPV6_MSG_RECONFIGURE ||
                        h->msg_type == DHCPV6_MSG_REPLY ||
                        h->msg_type == DHCPV6_MSG_ADVERTISE)
-               return; // Invalid message types for client
+               return; /* Invalid message types for client */
 
        syslog(LOG_NOTICE, "Got a DHCPv6-request");
 
-       // Construct our forwarding envelope
+       /* Construct our forwarding envelope */
        struct dhcpv6_relay_forward_envelope hdr = {
                .msg_type = DHCPV6_MSG_RELAY_FORW,
                .hop_count = 0,
@@ -462,33 +586,38 @@ static void relay_client_request(struct sockaddr_in6 *source,
                .relay_message_len = htons(len),
        };
 
-       if (h->msg_type == DHCPV6_MSG_RELAY_FORW) { // handle relay-forward
+       if (h->msg_type == DHCPV6_MSG_RELAY_FORW) { /* handle relay-forward */
                if (h->hop_count >= DHCPV6_HOP_COUNT_LIMIT)
                        return; // Invalid hop count
                else
                        hdr.hop_count = h->hop_count + 1;
        }
 
-       // use memcpy here as the destination fields are unaligned
+       /* use memcpy here as the destination fields are unaligned */
        uint32_t ifindex = iface->ifindex;
        memcpy(&hdr.peer_address, &source->sin6_addr, sizeof(struct in6_addr));
        memcpy(&hdr.interface_id_data, &ifindex, sizeof(ifindex));
 
-       // Detect public IP of slave interface to use as link-address
-       struct odhcpd_ipaddr ip;
-       if (odhcpd_get_interface_addresses(iface->ifindex, &ip, 1) < 1) {
-               // No suitable address! Is the slave not configured yet?
-               // Detect public IP of master interface and use it instead
-               // This is WRONG and probably violates the RFC. However
-               // otherwise we have a hen and egg problem because the
-               // slave-interface cannot be auto-configured.
-               if (odhcpd_get_interface_addresses(master->ifindex, &ip, 1) < 1)
-                       return; // Could not obtain a suitable address
+       /* Detect public IP of slave interface to use as link-address */
+       struct odhcpd_ipaddr *ip = relay_link_address(iface);
+       if (!ip) {
+               /* No suitable address! Is the slave not configured yet?
+                * Detect public IP of master interface and use it instead
+                * This is WRONG and probably violates the RFC. However
+                * otherwise we have a hen and egg problem because the
+                * slave-interface cannot be auto-configured. */
+               ip = relay_link_address(master);
+               if (!ip)
+                       return; /* Could not obtain a suitable address */
        }
-       memcpy(&hdr.link_address, &ip.addr, sizeof(hdr.link_address));
 
-       struct sockaddr_in6 dhcpv6_servers = {AF_INET6,
-                       htons(DHCPV6_SERVER_PORT), 0, ALL_DHCPV6_SERVERS, 0};
+       memcpy(&hdr.link_address, &ip->addr.in6, sizeof(hdr.link_address));
+
+       memset(&s, 0, sizeof(s));
+       s.sin6_family = AF_INET6;
+       s.sin6_port = htons(DHCPV6_SERVER_PORT);
+       inet_pton(AF_INET6, ALL_DHCPV6_SERVERS, &s.sin6_addr);
+
        struct iovec iov[2] = {{&hdr, sizeof(hdr)}, {(void*)data, len}};
-       odhcpd_send(iface->dhcpv6_event.uloop.fd, &dhcpv6_servers, iov, 2, master);
+       odhcpd_send(master->dhcpv6_event.uloop.fd, &s, iov, 2, master);
 }