iproute: Add magic cookie to route dump file

In order to somehow verify that a blob contains route dump a
4-bytes magic is put at the head of the data and is checked
on restore.

Magic digits are taken from Portland (OR) coordinates :) Is
there any more reliable way of generating such?

Signed-of-by: Pavel Emelyanov <xemul@parallels.com>

diff --git a/ip/iproute.c b/ip/iproute.c
index 522dd2873a09594081c0f23879bc8bd8ac3eb0f8..1cf341799f52709cb23d60f4184959619a5dc381 100644 (file)
--- a/ip/iproute.c
+++ b/ip/iproute.c
@@ -1063,6 +1063,8 @@ static int iproute_flush_cache(void)
        return 0;
 }
 
+static __u32 route_dump_magic = 0x45311224;
+
 int save_route(const struct sockaddr_nl *who, struct nlmsghdr *n, void *arg)
 {
        int ret;
@@ -1071,11 +1073,6 @@ int save_route(const struct sockaddr_nl *who, struct nlmsghdr *n, void *arg)
        struct rtattr *tb[RTA_MAX+1];
        int host_len = -1;
 
-       if (isatty(STDOUT_FILENO)) {
-               fprintf(stderr, "Not sending binary stream to stdout\n");
-               return -1;
-       }
-
        host_len = calc_host_len(r);
        len -= NLMSG_LENGTH(sizeof(*r));
        parse_rtattr(tb, RTA_MAX, RTM_RTA(r), len);
@@ -1092,6 +1089,24 @@ int save_route(const struct sockaddr_nl *who, struct nlmsghdr *n, void *arg)
        return ret == n->nlmsg_len ? 0 : ret;
 }
 
+static int save_route_prep(void)
+{
+       int ret;
+
+       if (isatty(STDOUT_FILENO)) {
+               fprintf(stderr, "Not sending binary stream to stdout\n");
+               return -1;
+       }
+
+       ret = write(STDOUT_FILENO, &route_dump_magic, sizeof(route_dump_magic));
+       if (ret != sizeof(route_dump_magic)) {
+               fprintf(stderr, "Can't write magic to dump file\n");
+               return -1;
+       }
+
+       return 0;
+}
+
 static int iproute_list_flush_or_save(int argc, char **argv, int action)
 {
        int do_ipv6 = preferred_family;
@@ -1100,9 +1115,12 @@ static int iproute_list_flush_or_save(int argc, char **argv, int action)
        unsigned int mark = 0;
        rtnl_filter_t filter_fn;
 
-       if (action == IPROUTE_SAVE)
+       if (action == IPROUTE_SAVE) {
+               if (save_route_prep())
+                       return -1;
+
                filter_fn = save_route;
-       else
+       } else
                filter_fn = print_route;
 
        iproute_reset_filter();
@@ -1520,8 +1538,30 @@ int restore_handler(const struct sockaddr_nl *nl, struct nlmsghdr *n, void *arg)
        return ret;
 }
 
+static int route_dump_check_magic(void)
+{
+       int ret;
+       __u32 magic = 0;
+
+       if (isatty(STDIN_FILENO)) {
+               fprintf(stderr, "Can't restore route dump from a terminal\n");
+               return -1;
+       }
+
+       ret = fread(&magic, sizeof(magic), 1, stdin);
+       if (magic != route_dump_magic) {
+               fprintf(stderr, "Magic mismatch (%d elems, %x magic)\n", ret, magic);
+               return -1;
+       }
+
+       return 0;
+}
+
 int iproute_restore(void)
 {
+       if (route_dump_check_magic())
+               exit(-1);
+
        exit(rtnl_from_file(stdin, &restore_handler, NULL));
 }