kernel_netlink: take IPV6_SUBTREES into account.

The linux kernel should be able to deal correctly with source-sensitive ipv6
route entries since 3.11 (when it is configured with IPV6_SUBTREES).  This patch
modify the kernel so that ipv6 route entries sent into the kernel are not pushed
in a different routing table.

The behavior for v4 doesn't change.

babeld.h

@@ -80,6 +80,12 @@ THE SOFTWARE.
 #endif
 #endif
 
+#ifdef IPV6_SUBTREES
+#define has_ipv6_subtrees 1
+#else
+#define has_ipv6_subtrees 0
+#endif
+
 extern struct timeval now;
 extern int debug;
 extern time_t reboot_time;

kernel_netlink.c

@@ -1013,6 +1013,8 @@ kernel_route(int operation, const unsigned char *dest, unsigned short plen,
     rtm = NLMSG_DATA(&buf.nh);
     rtm->rtm_family = ipv4 ? AF_INET : AF_INET6;
     rtm->rtm_dst_len = ipv4 ? plen - 96 : plen;
+    if(has_ipv6_subtrees && src && !ipv4)
+        rtm->rtm_src_len = src_plen;
     rtm->rtm_table = table;
     rtm->rtm_scope = RT_SCOPE_UNIVERSE;
     if(metric < KERNEL_INFINITY)
@@ -1034,6 +1036,12 @@ kernel_route(int operation, const unsigned char *dest, unsigned short plen,
         rta->rta_len = RTA_LENGTH(sizeof(struct in6_addr));
         rta->rta_type = RTA_DST;
         memcpy(RTA_DATA(rta), dest, sizeof(struct in6_addr));
+        if(has_ipv6_subtrees && src) {
+            rta = RTA_NEXT(rta, len);
+            rta->rta_len = RTA_LENGTH(sizeof(struct in6_addr));
+            rta->rta_type = RTA_SRC;
+            memcpy(RTA_DATA(rta), src, sizeof(struct in6_addr));
+        }
     }
 
     rta = RTA_NEXT(rta, len);
@@ -1073,19 +1081,16 @@ parse_kernel_route_rta(struct rtmsg *rtm, int len, struct kernel_route *route)
     struct rtattr *rta= RTM_RTA(rtm);;
     len -= NLMSG_ALIGN(sizeof(*rtm));
 
-    memset(&route->prefix, 0, sizeof(struct in6_addr));
-    memset(&route->gw, 0, sizeof(struct in6_addr));
-    route->plen = rtm->rtm_dst_len;
+    memset(route, 0, sizeof(struct kernel_route));
     if(rtm->rtm_family == AF_INET) {
+        /* if RTA_DST is not a TLV, that's a default destination */
         const unsigned char zeroes[4] = {0, 0, 0, 0};
         v4tov6(route->prefix, zeroes);
-        route->plen += 96;
+        route->plen = 96;
     }
-
-    route->metric = 0;
-    route->ifindex = 0;
     route->proto = rtm->rtm_protocol;
 
+#define GET_PLEN(p) (rtm->rtm_family == AF_INET) ? p + 96 : p
 #define COPY_ADDR(d, s) \
     do { \
         if(rtm->rtm_family == AF_INET6) \
@@ -1099,8 +1104,13 @@ parse_kernel_route_rta(struct rtmsg *rtm, int len, struct kernel_route *route)
     while(RTA_OK(rta, len)) {
         switch(rta->rta_type) {
         case RTA_DST:
+            route->plen = GET_PLEN(rtm->rtm_dst_len);
             COPY_ADDR(route->prefix, RTA_DATA(rta));
             break;
+        case RTA_SRC:
+            route->src_plen = GET_PLEN(rtm->rtm_src_len);
+            COPY_ADDR(route->src_prefix, RTA_DATA(rta));
+            break;
         case RTA_GATEWAY:
             COPY_ADDR(route->gw, RTA_DATA(rta));
             break;
@@ -1121,6 +1131,7 @@ parse_kernel_route_rta(struct rtmsg *rtm, int len, struct kernel_route *route)
         rta = RTA_NEXT(rta, len);
     }
 #undef COPY_ADDR
+#undef GET_PLEN
 
     int i;
     for(i = 0; i < import_table_count; i++)
@@ -1135,6 +1146,7 @@ print_kernel_route(int add, int protocol, int type,
 {
     char ifname[IFNAMSIZ];
     char addr_prefix[INET6_ADDRSTRLEN];
+    char src_addr_prefix[INET6_ADDRSTRLEN];
     char addr_gw[INET6_ADDRSTRLEN];
 
     if(!inet_ntop(AF_INET6, route->prefix,
@@ -1145,6 +1157,21 @@ print_kernel_route(int add, int protocol, int type,
         return;
     }
 
+    if(route->src_plen >= 0) {
+        if(!inet_ntop(AF_INET6, route->src_prefix,
+                      src_addr_prefix, sizeof(src_addr_prefix))) {
+            kdebugf("Couldn't format kernel route for printing.");
+            return;
+        }
+
+        kdebugf("%s kernel route: dest: %s/%d gw: %s metric: %d if: %s "
+                "(proto: %d, type: %d, from: %s/%d)",
+                add == RTM_NEWROUTE ? "Add" : "Delete",
+                addr_prefix, route->plen, addr_gw, route->metric, ifname,
+                protocol, type, src_addr_prefix, route->src_plen);
+        return;
+    }
+
     kdebugf("%s kernel route: dest: %s/%d gw: %s metric: %d if: %s "
            "(proto: %d, type: %d)",
            add == RTM_NEWROUTE ? "Add" : "Delete",
@@ -1189,9 +1216,6 @@ filter_kernel_routes(struct nlmsghdr *nh, void *data)
     if(rtm->rtm_protocol == RTPROT_BABEL)
         return 0;
 
-    if(rtm->rtm_src_len != 0)
-        return 0;
-
     /* Ignore cached routes, advertised by some kernels (linux 3.x). */
     if(rtm->rtm_flags & RTM_F_CLONED)
         return 0;
@@ -1205,7 +1229,8 @@ filter_kernel_routes(struct nlmsghdr *nh, void *data)
     if(rc < 0)
         return 0;
 
-    if(martian_prefix(current_route->prefix, current_route->plen))
+    if(martian_prefix(current_route->prefix, current_route->plen) ||
+       martian_prefix(current_route->src_prefix, current_route->src_plen))
         return 0;
 
     /* Ignore default unreachable routes; no idea where they come from. */
@@ -1778,6 +1803,9 @@ find_table(const unsigned char *src, unsigned short src_plen)
     struct kernel_table *kt = NULL;
     int i, new_i;
 
+    if(has_ipv6_subtrees && (src_plen < 96 || !v4mapped(src)))
+        return export_table;
+
     if(src_plen == 0)
         return export_table;