router: improve RA PIO search logic

We need to properly handle when the user modifies the prefix length
assigned to an interface by:
- Checking if the prefix matches the address taking into account:
    - The biggest length of address and PIO.
    - A minimum PIO of /64.
- Updating addresses and lengths for existing PIOs.

Signed-off-by: Álvaro Fernández Rojas <[email protected]>

diff --git a/src/router.c b/src/router.c
index 4fe8ccfb0fd0a687d3cbe2ec533a200a1138d905..31a4c339f5a49ea9231f2ba38a523ea55ea801eb 100644 (file)
--- a/src/router.c
+++ b/src/router.c
@@ -449,14 +449,20 @@ struct nd_opt_capt_portal {
 };
 
 /* IPv6 RA PIOs */
+inline static int router_compare_pio_addr(const struct ra_pio *pio, const struct odhcpd_ipaddr *addr)
+{
+       uint8_t cmp_len = max(64, max(pio->length, addr->prefix_len));
+
+       return odhcpd_bmemcmp(&pio->prefix, &addr->addr.in6, cmp_len);
+}
+
 static struct ra_pio *router_find_ra_pio(struct interface *iface,
        struct odhcpd_ipaddr *addr)
 {
        for (size_t i = 0; i < iface->pio_cnt; i++) {
                struct ra_pio *cur_pio = &iface->pios[i];
 
-               if (addr->prefix_len == cur_pio->length &&
-                   !odhcpd_bmemcmp(&addr->addr.in6, &cur_pio->prefix, cur_pio->length))
+               if (!router_compare_pio_addr(cur_pio, addr))
                        return cur_pio;
        }
 
@@ -471,6 +477,23 @@ static void router_add_ra_pio(struct interface *iface,
 
        pio = router_find_ra_pio(iface, addr);
        if (pio) {
+               if (memcmp(&pio->prefix, &addr->addr.in6, sizeof(struct in6_addr)) != 0 ||
+                   pio->length != addr->prefix_len)
+               {
+                       char new_ipv6_str[INET6_ADDRSTRLEN];
+
+                       iface->pio_update = true;
+                       warn("rfc9096: %s: changed %s/%u -> %s/%u",
+                            iface->ifname,
+                            inet_ntop(AF_INET6, &pio->prefix, ipv6_str, sizeof(ipv6_str)),
+                            pio->length,
+                            inet_ntop(AF_INET6, &addr->addr.in6, new_ipv6_str, sizeof(new_ipv6_str)),
+                            addr->prefix_len);
+
+                       memcpy(&pio->prefix, &addr->addr.in6, sizeof(struct in6_addr));
+                       pio->length = addr->prefix_len;
+               }
+
                if (pio->lifetime) {
                        pio->lifetime = 0;
 
@@ -492,7 +515,7 @@ static void router_add_ra_pio(struct interface *iface,
        pio = &iface->pios[iface->pio_cnt];
        iface->pio_cnt++;
 
-       memcpy(&pio->prefix, &addr->addr.in6, sizeof(pio->prefix));
+       memcpy(&pio->prefix, &addr->addr.in6, sizeof(struct in6_addr));
        pio->length = addr->prefix_len;
        pio->lifetime = 0;
 
@@ -659,8 +682,7 @@ static int send_router_advert(struct interface *iface, const struct in6_addr *fr
                        for (size_t j = 0; j < valid_addr_cnt; j++) {
                                struct odhcpd_ipaddr *cur_addr = &addrs[j];
 
-                               if (cur_pio->length == cur_addr->prefix_len &&
-                                   !odhcpd_bmemcmp(&cur_pio->prefix, &cur_addr->addr.in6, cur_pio->length)) {
+                               if (!router_compare_pio_addr(cur_pio, cur_addr)) {
                                        pio_found = true;
                                        break;
                                }