Rate limit router advertisements according to RFC 4861 6.2.6. In

particular make sure to send at most one multicast advertisement every
three seconds.
input & OK deraadt

diff --git a/usr.sbin/rad/engine.c b/usr.sbin/rad/engine.c
index 7c999bc..dddff2d 100644 (file)
--- a/usr.sbin/rad/engine.c
+++ b/usr.sbin/rad/engine.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: engine.c,v 1.19 2021/05/13 11:22:15 florian Exp $     */
+/*     $OpenBSD: engine.c,v 1.20 2022/03/23 15:26:08 florian Exp $     */
 
 /*
  * Copyright (c) 2018 Florian Obser <florian@openbsd.org>
@@ -23,6 +23,7 @@
 #include <sys/queue.h>
 #include <sys/socket.h>
 #include <sys/syslog.h>
+#include <sys/time.h>
 #include <sys/uio.h>
 
 #include <netinet/in.h>
@@ -33,10 +34,11 @@
 #include <errno.h>
 #include <event.h>
 #include <imsg.h>
+#include <pwd.h>
 #include <signal.h>
 #include <stdlib.h>
 #include <string.h>
-#include <pwd.h>
+#include <time.h>
 #include <unistd.h>
 
 #include "log.h"
@@ -46,7 +48,9 @@
 struct engine_iface {
        TAILQ_ENTRY(engine_iface)       entry;
        struct event                    timer;
+       struct timespec                 last_ra;
        uint32_t                        if_index;
+       int                             ras_delayed;
 };
 
 TAILQ_HEAD(, engine_iface)     engine_interfaces;
@@ -464,20 +468,21 @@ void
 parse_rs(struct imsg_ra_rs *rs)
 {
        struct nd_router_solicit        *nd_rs;
-       struct imsg_send_ra              send_ra;
+       struct engine_iface             *engine_iface;
        ssize_t                          len;
+       int                              unicast_ra = 0;
        const char                      *hbuf;
        char                             ifnamebuf[IFNAMSIZ];
        uint8_t                         *p;
 
        hbuf = sin6_to_str(&rs->from);
 
-       send_ra.if_index = rs->if_index;
-       memcpy(&send_ra.to, &all_nodes, sizeof(send_ra.to));
-
        log_debug("got RS from %s on %s", hbuf, if_indextoname(rs->if_index,
            ifnamebuf));
 
+       if ((engine_iface = find_engine_iface_by_id(rs->if_index)) == NULL)
+               return;
+
        len = rs->len;
 
        if (!(IN6_IS_ADDR_LINKLOCAL(&rs->from.sin6_addr) ||
@@ -517,7 +522,7 @@ parse_rs(struct imsg_ra_rs *rs)
                switch (nd_opt_hdr->nd_opt_type) {
                case ND_OPT_SOURCE_LINKADDR:
                        log_debug("got RS with source linkaddr option");
-                       memcpy(&send_ra.to, &rs->from, sizeof(send_ra.to));
+                       unicast_ra = 1;
                        break;
                default:
                        log_debug("\t\tUNKNOWN: %d", nd_opt_hdr->nd_opt_type);
@@ -526,8 +531,34 @@ parse_rs(struct imsg_ra_rs *rs)
                len -= nd_opt_hdr->nd_opt_len * 8 - 2;
                p += nd_opt_hdr->nd_opt_len * 8 - 2;
        }
-       engine_imsg_compose_frontend(IMSG_SEND_RA, 0, &send_ra,
-           sizeof(send_ra));
+
+       if (unicast_ra) {
+               struct imsg_send_ra      send_ra;
+
+               send_ra.if_index = rs->if_index;
+               memcpy(&send_ra.to, &rs->from, sizeof(send_ra.to));
+               engine_imsg_compose_frontend(IMSG_SEND_RA, 0, &send_ra,
+                   sizeof(send_ra));
+       } else {
+               struct timespec  now, diff, ra_delay = {MIN_DELAY_BETWEEN_RAS, 0};
+               struct timeval   tv = {0, 0};
+
+               /* a multicast RA is already scheduled within the next 3 seconds */
+               if (engine_iface->ras_delayed)
+                       return;
+
+               engine_iface->ras_delayed = 1;
+               clock_gettime(CLOCK_MONOTONIC, &now);
+               timespecsub(&now, &engine_iface->last_ra, &diff);
+
+               if (timespeccmp(&diff, &ra_delay, <)) {
+                       timespecsub(&ra_delay, &diff, &ra_delay);
+                       TIMESPEC_TO_TIMEVAL(&tv, &ra_delay);
+               }
+
+               tv.tv_usec = arc4random_uniform(MAX_RA_DELAY_TIME * 1000);
+               evtimer_add(&engine_iface->timer, &tv);
+       }
 }
 
 struct engine_iface*
@@ -607,4 +638,6 @@ iface_timeout(int fd, short events, void *arg)
        memcpy(&send_ra.to, &all_nodes, sizeof(send_ra.to));
        engine_imsg_compose_frontend(IMSG_SEND_RA, 0, &send_ra,
            sizeof(send_ra));
+       clock_gettime(CLOCK_MONOTONIC, &engine_iface->last_ra);
+       engine_iface->ras_delayed = 0;
 }

diff --git a/usr.sbin/rad/rad.h b/usr.sbin/rad/rad.h
index d6fdaf5..9b0fedd 100644 (file)
--- a/usr.sbin/rad/rad.h
+++ b/usr.sbin/rad/rad.h
@@ -1,4 +1,4 @@
-/*     $OpenBSD: rad.h,v 1.21 2021/02/27 10:35:20 florian Exp $        */
+/*     $OpenBSD: rad.h,v 1.22 2022/03/23 15:26:08 florian Exp $        */
 
 /*
  * Copyright (c) 2018 Florian Obser <florian@openbsd.org>
@@ -30,7 +30,9 @@
 #define        MIN_RTR_ADV_INTERVAL    200
 #define        ADV_DEFAULT_LIFETIME    3 * MAX_RTR_ADV_INTERVAL
 #define        ADV_PREFERRED_LIFETIME  604800  /* 7 days */
-#define ADV_VALID_LIFETIME     2592000 /* 30 days */
+#define        ADV_VALID_LIFETIME      2592000 /* 30 days */
+#define        MAX_RA_DELAY_TIME       500     /* 500 milliseconds */
+#define        MIN_DELAY_BETWEEN_RAS   3       /* 3 seconds */
 #define        MAX_SEARCH              1025    /* MAXDNAME in arpa/nameser.h */
 #define        DEFAULT_RDNS_LIFETIME   600 * 1.5