Implement last remaining bits to update from RFC 4941 to RFC 8981.

The desync factor is now tracked per temporary IP and the max value
has been increased to about 9 hours.
While here fix a bug where the minimum acceptable pltime in a router
advertisement should be bigger than PRIV_REGEN_ADVANCE not the desync
factor (which didn't make any sense at all).

From Fernando Gont, thanks!
OK sthen

diff --git a/sbin/slaacd/engine.c b/sbin/slaacd/engine.c
index 4160d79..2d19ab8 100644 (file)
--- a/sbin/slaacd/engine.c
+++ b/sbin/slaacd/engine.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: engine.c,v 1.61 2021/03/02 17:17:15 florian Exp $     */
+/*     $OpenBSD: engine.c,v 1.62 2021/03/06 19:02:53 florian Exp $     */
 
 /*
  * Copyright (c) 2017 Florian Obser <florian@openbsd.org>
@@ -88,10 +88,14 @@
 #define        RTR_SOLICITATION_INTERVAL       4
 #define        MAX_RTR_SOLICITATIONS           3
 
-/* constants for RFC 4941 autoconf privacy extension */
-#define PRIV_MAX_DESYNC_FACTOR 600     /* 10 minutes */
+/*
+ * Constants for RFC 8981 autoconf privacy extensions
+ *
+ * PRIV_PREFERRED_LIFETIME > (PRIV_MAX_DESYNC_FACTOR + PRIV_REGEN_ADVANCE)
+ */
 #define PRIV_VALID_LIFETIME    172800  /* 2 days */
 #define PRIV_PREFERRED_LIFETIME        86400   /* 1 day */
+#define PRIV_MAX_DESYNC_FACTOR 34560   /* PRIV_PREFERRED_LIFETIME * 0.4 */
 #define        PRIV_REGEN_ADVANCE      5       /* 5 seconds */
 
 enum if_state {
@@ -198,6 +202,7 @@ struct address_proposal {
        uint8_t                          prefix_len;
        uint32_t                         vltime;
        uint32_t                         pltime;
+       uint32_t                         desync_factor;
        uint8_t                          soiikey[SLAACD_SOIIKEY_LEN];
        uint32_t                         mtu;
 };
@@ -327,8 +332,6 @@ static struct imsgev        *iev_frontend;
 static struct imsgev   *iev_main;
 int64_t                         proposal_id;
 
-uint32_t                desync_factor;
-
 void
 engine_sig_handler(int sig, short event, void *arg)
 {
@@ -399,8 +402,6 @@ engine(int debug, int verbose)
 
        LIST_INIT(&slaacd_interfaces);
 
-       desync_factor = arc4random_uniform(PRIV_MAX_DESYNC_FACTOR);
-
        event_dispatch();
 
        engine_shutdown();
@@ -1858,14 +1859,18 @@ update_iface_ra_prefix(struct slaacd_iface *iface, struct radv *ra,
 
                if (addr_proposal->privacy) {
                        struct timespec now;
-                       int64_t         ltime;
+                       int64_t         ltime, mtime;
 
                        if (clock_gettime(CLOCK_MONOTONIC, &now))
                                fatal("clock_gettime");
 
-                       ltime = MINIMUM(addr_proposal->created.tv_sec +
-                           PRIV_PREFERRED_LIFETIME - desync_factor,
-                           now.tv_sec + prefix->pltime) - now.tv_sec;
+                       mtime = addr_proposal->created.tv_sec +
+                           PRIV_PREFERRED_LIFETIME -
+                           addr_proposal->desync_factor;
+
+                       ltime = MINIMUM(mtime, now.tv_sec + prefix->pltime) -
+                           now.tv_sec;
+
                        pltime = ltime > 0 ? ltime : 0;
 
                        ltime = MINIMUM(addr_proposal->created.tv_sec +
@@ -1873,7 +1878,7 @@ update_iface_ra_prefix(struct slaacd_iface *iface, struct radv *ra,
                            now.tv_sec;
                        vltime = ltime > 0 ? ltime : 0;
 
-                       if (pltime > PRIV_REGEN_ADVANCE)
+                       if ((mtime - now.tv_sec) > PRIV_REGEN_ADVANCE)
                                found_privacy = 1;
                } else {
                        pltime = prefix->pltime;
@@ -1919,11 +1924,11 @@ update_iface_ra_prefix(struct slaacd_iface *iface, struct radv *ra,
 
        /* privacy addresses do not depend on eui64 */
        if (!found_privacy && iface->autoconfprivacy) {
-               if (prefix->pltime < desync_factor) {
+               if (prefix->pltime < PRIV_REGEN_ADVANCE) {
                        log_warnx("%s: pltime from %s is too small: %d < %d; "
                            "not generating privacy address", __func__,
                            sin6_to_str(&ra->from), prefix->pltime,
-                           desync_factor);
+                           PRIV_REGEN_ADVANCE);
                } else
                        /* new privacy proposal */
                        gen_address_proposal(iface, ra, prefix, 1);
@@ -2055,8 +2060,11 @@ gen_address_proposal(struct slaacd_iface *iface, struct radv *ra, struct
        if (privacy) {
                addr_proposal->vltime = MINIMUM(prefix->vltime,
                    PRIV_VALID_LIFETIME);
+               addr_proposal->desync_factor =
+                   arc4random_uniform(PRIV_MAX_DESYNC_FACTOR);
+
                addr_proposal->pltime = MINIMUM(prefix->pltime,
-                   PRIV_PREFERRED_LIFETIME - desync_factor);
+                   PRIV_PREFERRED_LIFETIME - addr_proposal->desync_factor);
        } else {
                addr_proposal->vltime = prefix->vltime;
                addr_proposal->pltime = prefix->pltime;

diff --git a/sbin/slaacd/slaacd.8 b/sbin/slaacd/slaacd.8
index fb9bb3d..eec7187 100644 (file)
--- a/sbin/slaacd/slaacd.8
+++ b/sbin/slaacd/slaacd.8
@@ -1,4 +1,4 @@
-.\"    $OpenBSD: slaacd.8,v 1.10 2018/07/23 11:51:38 florian Exp $
+.\"    $OpenBSD: slaacd.8,v 1.11 2021/03/06 19:02:53 florian Exp $
 .\"
 .\" Copyright (c) 2017 Florian Obser <florian@openbsd.org>
 .\" Copyright (c) 2016 Kenneth R Westerback <kwesterback@gmail.com>
@@ -15,7 +15,7 @@
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
-.Dd $Mdocdate: July 23 2018 $
+.Dd $Mdocdate: March 6 2021 $
 .Dt SLAACD 8
 .Os
 .Sh NAME
@@ -110,15 +110,6 @@ socket used for communication with
 .Re
 .Pp
 .Rs
-.%A T. Narten
-.%A R. Draves
-.%A S. Krishnan
-.%D September 2007
-.%R RFC 4941
-.%T Privacy Extensions for Stateless Address Autoconfiguration in IPv6
-.Re
-.Pp
-.Rs
 .%A F. Gont
 .%D April 2014
 .%R RFC 7217
@@ -152,6 +143,16 @@ socket used for communication with
 .%R RFC 8106
 .%T IPv6 Router Advertisement Options for DNS Configuration
 .Re
+.Pp
+.Rs
+.%A F. Gont
+.%A S. Krishnan
+.%A T. Narten
+.%A R. Draves
+.%D February 2021
+.%R RFC 8981
+.%T Temporary Address Extensions for Stateless Address Autoconfiguration in IPv6
+.Re
 .Sh HISTORY
 The
 .Nm