Linux: Use netlink to workout address flags

There seems to be a race with netlink announcing the address vs
it's availability via /proc.
Fixes #76.

diff --git a/src/if-linux.c b/src/if-linux.c
index b642ab30617b8eb62e8a9ec81a0168c8b940fc06..c3bfd03dc0ccea806a91af1ff4efc1a0ecacfe47 100644 (file)
--- a/src/if-linux.c
+++ b/src/if-linux.c
@@ -161,7 +161,6 @@ static const uint8_t ipv4_bcast_addr[] = {
 
 static int if_addressexists(struct interface *, struct in_addr *);
 
-#define PROC_INET6     "/proc/net/if_inet6"
 #define PROC_PROMOTE   "/proc/sys/net/ipv4/conf/%s/promote_secondaries"
 #define SYS_BRIDGE     "/sys/class/net/%s/bridge/bridge_id"
 #define SYS_LAYER2     "/sys/class/net/%s/device/layer2"
@@ -1974,46 +1973,73 @@ if_address6(unsigned char cmd, const struct ipv6_addr *ia)
            NULL, NULL);
 }
 
+struct ifiaddr6
+{
+       unsigned int ifa_ifindex;
+       struct in6_addr ifa_addr;
+       uint32_t ifa_flags;
+       bool ifa_found;
+};
+
+static int
+_if_addrflags6(__unused struct dhcpcd_ctx *ctx,
+    void *arg, struct nlmsghdr *nlm)
+{
+       struct ifiaddr6 *ia = arg;
+       size_t len;
+       struct rtattr *rta;
+       struct ifaddrmsg *ifa;
+       bool matches_addr = false;
+
+       ifa = NLMSG_DATA(nlm);
+       if (ifa->ifa_index != ia->ifa_ifindex || ifa->ifa_family != AF_INET6)
+               return 0;
+
+       rta = IFA_RTA(ifa);
+       len = NLMSG_PAYLOAD(nlm, sizeof(*ifa));
+       for (; RTA_OK(rta, len); rta = RTA_NEXT(rta, len)) {
+               switch (rta->rta_type) {
+               case IFA_ADDRESS:
+                       if (IN6_ARE_ADDR_EQUAL(&ia->ifa_addr, RTA_DATA(rta)))
+                               ia->ifa_found = matches_addr = true;
+                       else
+                               matches_addr = false;
+                       break;
+               case IFA_FLAGS:
+                       if (matches_addr)
+                               memcpy(&ia->ifa_flags, RTA_DATA(rta), sizeof(ia->ifa_flags));
+                       break;
+               }
+       }
+       return 0;
+}
+
 int
 if_addrflags6(const struct interface *ifp, const struct in6_addr *addr,
     __unused const char *alias)
 {
-       char buf[PS_BUFLEN], *bp = buf, *line;
-       ssize_t buflen;
-       char *p, ifaddress[33], address[33], name[IF_NAMESIZE + 1];
-       unsigned int ifindex;
-       int prefix, scope, flags, i;
+       struct ifiaddr6 ia = {
+               .ifa_ifindex = ifp->index,
+               .ifa_addr = *addr,
+               .ifa_found = false,
+       };
+       struct nlma nlm = {
+           .hdr.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifaddrmsg)),
+           .hdr.nlmsg_type = RTM_GETADDR,
+           .hdr.nlmsg_flags = NLM_F_REQUEST | NLM_F_MATCH,
+           .ifa.ifa_family = AF_INET6,
+           .ifa.ifa_index = ifp->index,
+       };
 
-       buflen = dhcp_readfile(ifp->ctx, PROC_INET6, buf, sizeof(buf));
-       if (buflen == -1)
+       int error = if_sendnetlink(ifp->ctx, NETLINK_ROUTE, &nlm.hdr,
+           &_if_addrflags6, &ia);
+       if (error == -1)
                return -1;
-       if ((size_t)buflen == sizeof(buf)) {
-               errno = ENOBUFS;
+       if (!ia.ifa_found) {
+               errno = ESRCH;
                return -1;
        }
-
-       p = ifaddress;
-       for (i = 0; i < (int)sizeof(addr->s6_addr); i++) {
-               p += snprintf(p, 3, "%.2x", addr->s6_addr[i]);
-       }
-       *p = '\0';
-
-       while ((line = get_line(&bp, &buflen)) != NULL) {
-               if (sscanf(line,
-                   "%32[a-f0-9] %x %x %x %x %"TOSTRING(IF_NAMESIZE)"s\n",
-                   address, &ifindex, &prefix, &scope, &flags, name) != 6 ||
-                   strlen(address) != 32)
-               {
-                       errno = EINVAL;
-                       return -1;
-               }
-               if (strcmp(name, ifp->name) == 0 &&
-                   strcmp(ifaddress, address) == 0)
-                       return flags;
-       }
-
-       errno = ESRCH;
-       return -1;
+       return (int)ia.ifa_flags;
 }
 
 int