ctdb-daemon: Gratuitous ARP equivalent for IPv6 is neighbor advertisement

Not neighbour solicitation.  See:

  https://tools.ietf.org/html/rfc4861#section-4.4

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>

diff --git a/ctdb/common/system_linux.c b/ctdb/common/system_linux.c
index 9aaa1fdd7cea8ab25d292e70f435e4432a65b71e..97a57ac8b6596c47414185472defb13e9446e044 100644 (file)
--- a/ctdb/common/system_linux.c
+++ b/ctdb/common/system_linux.c
@@ -75,9 +75,14 @@ int ctdb_sys_send_arp(const ctdb_sock_addr *addr, const char *iface)
        struct ether_header *eh;
        struct arphdr *ah;
        struct ip6_hdr *ip6;
-       struct nd_neighbor_solicit *nd_ns;
+       struct nd_neighbor_advert *nd_na;
+       struct nd_opt_hdr *nd_oh;
        struct ifreq if_hwaddr;
-       unsigned char buffer[78]; /* ipv6 neigh solicitation size */
+       /* Size of IPv6 neighbor advertisement (with option) */
+       unsigned char buffer[sizeof(struct ether_header) +
+                            sizeof(struct ip6_hdr) +
+                            sizeof(struct nd_neighbor_advert) +
+                            sizeof(struct nd_opt_hdr) + ETH_ALEN];
        char *ptr;
        char bdcast[] = {0xff,0xff,0xff,0xff,0xff,0xff};
        struct ifreq ifr;
@@ -219,31 +224,45 @@ int ctdb_sys_send_arp(const ctdb_sock_addr *addr, const char *iface)
 
                memset(buffer, 0 , sizeof(buffer));
                eh = (struct ether_header *)buffer;
-               memset(eh->ether_dhost, 0xff, ETH_ALEN);
+               /* Ethernet multicast: 33:33:00:00:00:01 (see RFC2464,
+                * section 7) - note zeroes above! */
+               eh->ether_dhost[0] = eh->ether_dhost[1] = 0x33;
+               eh->ether_dhost[5] = 0x01;
                memcpy(eh->ether_shost, if_hwaddr.ifr_hwaddr.sa_data, ETH_ALEN);
                eh->ether_type = htons(ETHERTYPE_IP6);
 
                ip6 = (struct ip6_hdr *)(eh+1);
                ip6->ip6_vfc  = 0x60;
-               ip6->ip6_plen = htons(sizeof(*nd_ns));
+               ip6->ip6_plen = htons(sizeof(*nd_na) +
+                                     sizeof(struct nd_opt_hdr) +
+                                     ETH_ALEN);
                ip6->ip6_nxt  = IPPROTO_ICMPV6;
                ip6->ip6_hlim = 255;
-               ip6->ip6_dst  = addr->ip6.sin6_addr;
-
-               nd_ns = (struct nd_neighbor_solicit *)(ip6+1);
-               nd_ns->nd_ns_type = ND_NEIGHBOR_SOLICIT;
-               nd_ns->nd_ns_code = 0;
-               nd_ns->nd_ns_reserved = 0;
-               nd_ns->nd_ns_target = addr->ip6.sin6_addr;
-
-               nd_ns->nd_ns_cksum = tcp_checksum6((uint16_t *)nd_ns, ntohs(ip6->ip6_plen), ip6);
+               ip6->ip6_src  = addr->ip6.sin6_addr;
+               /* all-nodes multicast */
+               inet_pton(AF_INET6, "ff02::1", &ip6->ip6_dst);
+
+               nd_na = (struct nd_neighbor_advert *)(ip6+1);
+               nd_na->nd_na_type = ND_NEIGHBOR_ADVERT;
+               nd_na->nd_na_code = 0;
+               nd_na->nd_na_flags_reserved = ND_NA_FLAG_OVERRIDE;
+               nd_na->nd_na_target = addr->ip6.sin6_addr;
+               /* Option: Target link-layer address */
+               nd_oh = (struct nd_opt_hdr *)(nd_na+1);
+               nd_oh->nd_opt_type = ND_OPT_TARGET_LINKADDR;
+               nd_oh->nd_opt_len = 1;
+               memcpy(&(nd_oh+1)[0], if_hwaddr.ifr_hwaddr.sa_data, ETH_ALEN);
+
+               nd_na->nd_na_cksum = tcp_checksum6((uint16_t *)nd_na,
+                                                  ntohs(ip6->ip6_plen), ip6);
 
                sall.sll_family = AF_PACKET;
                sall.sll_halen = 6;
-               memcpy(&sall.sll_addr[0], bdcast, sall.sll_halen);
+               memcpy(&sall.sll_addr[0], &eh->ether_dhost[0], sall.sll_halen);
                sall.sll_protocol = htons(ETH_P_ALL);
                sall.sll_ifindex = ifr.ifr_ifindex;
-               ret = sendto(s, buffer, 78, 0, (struct sockaddr *)&sall, sizeof(sall));
+               ret = sendto(s, buffer, sizeof(buffer),
+                            0, (struct sockaddr *)&sall, sizeof(sall));
                if (ret < 0 ){
                        close(s);
                        DEBUG(DEBUG_CRIT,(__location__ " failed sendto\n"));