Merge pull request #28328 from yuwata/network-ndisc-limit-captive-portal

network: limit number of captive portals by RA

1 files changed, 30 insertions, 4 deletions

diff --git a/src/network/networkd-ndisc.c b/src/network/networkd-ndisc.c
index c6ca7f95e2..ae267ce5ca 100644
--- a/src/network/networkd-ndisc.c
+++ b/src/network/networkd-ndisc.c
@@ -27,6 +27,9 @@
 
 #define NDISC_DNSSL_MAX 64U
 #define NDISC_RDNSS_MAX 64U
+/* Not defined RFC, but let's set an upper limit to make not consume much memory.
+ * This should be safe as typically there should be at most 1 portal per network. */
+#define NDISC_CAPTIVE_PORTAL_MAX 64U
 
 bool link_ipv6_accept_ra_enabled(Link *link) {
         assert(link);
@@ -897,21 +900,34 @@ static int ndisc_router_process_captive_portal(Link *link, sd_ndisc_router *rt)
                 return log_link_warning_errno(link, r, "Failed to get captive portal from RA: %m");
 
         if (len == 0)
-                return 0;
+                return log_link_warning_errno(link, SYNTHETIC_ERRNO(EBADMSG), "Received empty captive portal, ignoring.");
 
         r = make_cstring(uri, len, MAKE_CSTRING_REFUSE_TRAILING_NUL, &captive_portal);
         if (r < 0)
                 return log_link_warning_errno(link, r, "Failed to convert captive portal URI: %m");
 
         if (!in_charset(captive_portal, URI_VALID))
-                return log_link_debug_errno(link, SYNTHETIC_ERRNO(EBADMSG), "Received invalid captive portal, ignoring.");
+                return log_link_warning_errno(link, SYNTHETIC_ERRNO(EBADMSG), "Received invalid captive portal, ignoring.");
 
         exist = set_get(link->ndisc_captive_portals, &(NDiscCaptivePortal) { .captive_portal = captive_portal });
         if (exist) {
                 /* update existing entry */
                 exist->router = router;
                 exist->lifetime_usec = lifetime_usec;
-                return 0;
+                return 1;
+        }
+
+        if (set_size(link->ndisc_captive_portals) >= NDISC_CAPTIVE_PORTAL_MAX) {
+                NDiscCaptivePortal *c, *target = NULL;
+
+                /* Find the portal who has the minimal lifetime and drop it to store new one. */
+                SET_FOREACH(c, link->ndisc_captive_portals)
+                        if (!target || c->lifetime_usec < target->lifetime_usec)
+                                target = c;
+
+                assert(target);
+                assert(set_remove(link->ndisc_captive_portals, target) == target);
+                ndisc_captive_portal_free(target);
         }
 
         new_entry = new(NDiscCaptivePortal, 1);
@@ -931,10 +947,11 @@ static int ndisc_router_process_captive_portal(Link *link, sd_ndisc_router *rt)
         TAKE_PTR(new_entry);
 
         link_dirty(link);
-        return 0;
+        return 1;
 }
 
 static int ndisc_router_process_options(Link *link, sd_ndisc_router *rt) {
+        size_t n_captive_portal = 0;
         int r;
 
         assert(link);
@@ -970,7 +987,16 @@ static int ndisc_router_process_options(Link *link, sd_ndisc_router *rt) {
                         r = ndisc_router_process_dnssl(link, rt);
                         break;
                 case SD_NDISC_OPTION_CAPTIVE_PORTAL:
+                        if (n_captive_portal > 0) {
+                                if (n_captive_portal == 1)
+                                        log_link_notice(link, "Received RA with multiple captive portals, only using the first one.");
+
+                                n_captive_portal++;
+                                continue;
+                        }
                         r = ndisc_router_process_captive_portal(link, rt);
+                        if (r > 0)
+                                n_captive_portal++;
                         break;
                 }
                 if (r < 0 && r != -EBADMSG)