ip route: restore route entries in correct order

Sometimes we cannot restore route entries, because in kernel
  [1] fib_check_nh()
  [2] fib_valid_prefsrc()
cause some routes to depend on existence of others while adding.

For example, we saved all the routes, and flushed all tables
  [a] default via 192.168.122.1 dev eth0
  [b] 192.168.122.0/24 dev eth0 src 192.168.122.21
  [c] broadcast 127.0.0.0 dev lo table local src 127.0.0.1
  [d] local 127.0.0.0/8 dev lo table local  src 127.0.0.1
  [e] local 127.0.0.1 dev lo table local src 127.0.0.1
  [f] broadcast 127.255.255.255 dev lo table local src 127.0.0.1
  [g] broadcast 192.168.122.0 dev eth0 table local src 192.168.122.21
  [h] local 192.168.122.21 dev eth0 table local src 192.168.122.21
  [i] broadcast 192.168.122.255 dev eth0 table local src 192.168.122.21

  Now start to restore them:
    If we want to add [a], we have to add [b] first, as [1] and
    'via 192.168.122.1' in [a].
    If we want to add [b], we have to add [h] first, as [2] and
    'src 192.168.122.21' in [b].

  So the correct order to restore should be like:
    [e][h] -> [b][c][d][f][g][i] -> [a]

This patch fixes it by traversing the file 3 times, it only restores
part of them in each run according to the following conditions, to
make sure every entry can be restored successfully.
  1. !gw && (!fib_prefsrc || fib_prefsrc == cfg->fc_dst)
  2. !gw && (fib_prefsrc != cfg->fc_dst)
  3. gw

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Phil Sutter <phil@nwl.cc>

diff --git a/ip/iproute.c b/ip/iproute.c
index 24f6b010108191fb3be9b4394758b9338bad9075..c73500095cd38e6f1960d57a3d5caf42931d3d76 100644 (file)
--- a/ip/iproute.c
+++ b/ip/iproute.c
@@ -1810,12 +1810,42 @@ static int iproute_get(int argc, char **argv)
        return 0;
 }
 
+static int rtattr_cmp(struct rtattr *rta1, struct rtattr *rta2)
+{
+       if (!rta1 || !rta2 || rta1->rta_len != rta2->rta_len)
+               return 1;
+
+       return memcmp(RTA_DATA(rta1), RTA_DATA(rta2), RTA_PAYLOAD(rta1));
+}
+
 static int restore_handler(const struct sockaddr_nl *nl,
                           struct rtnl_ctrl_data *ctrl,
                           struct nlmsghdr *n, void *arg)
 {
-       int ret;
+       struct rtmsg *r = NLMSG_DATA(n);
+       struct rtattr *tb[RTA_MAX+1];
+       int len = n->nlmsg_len - NLMSG_LENGTH(sizeof(*r));
+       int ret, prio = *(int *)arg;
+
+       parse_rtattr(tb, RTA_MAX, RTM_RTA(r), len);
 
+       /* Restore routes in correct order:
+        * 0. ones for local addresses,
+        * 1. ones for local networks,
+        * 2. others (remote networks/hosts).
+        */
+       if (!prio && !tb[RTA_GATEWAY] && (!tb[RTA_PREFSRC] ||
+           !rtattr_cmp(tb[RTA_PREFSRC], tb[RTA_DST])))
+               goto restore;
+       else if (prio == 1 && !tb[RTA_GATEWAY] &&
+                rtattr_cmp(tb[RTA_PREFSRC], tb[RTA_DST]))
+               goto restore;
+       else if (prio == 2 && tb[RTA_GATEWAY])
+               goto restore;
+
+       return 0;
+
+restore:
        n->nlmsg_flags |= NLM_F_REQUEST | NLM_F_CREATE | NLM_F_ACK;
 
        ll_init_map(&rth);
@@ -1848,10 +1878,23 @@ static int route_dump_check_magic(void)
 
 static int iproute_restore(void)
 {
+       int pos, prio;
+
        if (route_dump_check_magic())
                exit(-1);
 
-       exit(rtnl_from_file(stdin, &restore_handler, NULL));
+       pos = ftell(stdin);
+       for (prio = 0; prio < 3; prio++) {
+               int err;
+
+               err = rtnl_from_file(stdin, &restore_handler, &prio);
+               if (err)
+                       exit(err);
+
+               fseek(stdin, pos, SEEK_SET);
+       }
+
+       exit(0);
 }
 
 static int show_handler(const struct sockaddr_nl *nl,