ipv6: set neighbor parameters from RAs

IPv6 router advertisement messages contain the following parameters
(RFC 4861):

 - Reachable time: 32-bit unsigned integer.  The time, in
   milliseconds, that a node assumes a neighbor is reachable after
   having received a reachability confirmation.  Used by the Neighbor
   Unreachability Detection algorithm.  A value of zero means
   unspecified (by this router).

 - Retrans Timer: 32-bit unsigned integer.  The time, in milliseconds,
   between retransmitted Neighbor Solicitation messages.  Used by
   address resolution and the Neighbor Unreachability Detection
   algorithm.   A value of zero means unspecified (by this router).

Currently NM ignores them; however, since it leaves accept_ra=1, the
kernel parses RAs and applies those parameters for us [1].

In the next commit kernel handling of RAs will be disabled, so let NM
set those neighbor-related parameters.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/net/ipv6/ndisc.c?h=v5.2#n1353

7 files changed, 103 insertions, 0 deletions

diff --git a/src/devices/nm-device.c b/src/devices/nm-device.c
index 5262670886..fb8ac91f34 100644
--- a/src/devices/nm-device.c
+++ b/src/devices/nm-device.c
@@ -9658,6 +9658,18 @@ ndisc_config_changed (NMNDisc *ndisc, const NMNDiscData *rdata, guint changed_in
 	if (changed & NM_NDISC_CONFIG_HOP_LIMIT)
 		nm_platform_sysctl_ip_conf_set_ipv6_hop_limit_safe (nm_device_get_platform (self), nm_device_get_ip_iface (self), rdata->hop_limit);
 
+	if (changed & NM_NDISC_CONFIG_REACHABLE_TIME) {
+		nm_platform_sysctl_ip_neigh_set_ipv6_reachable_time (nm_device_get_platform (self),
+		                                                     nm_device_get_ip_iface (self),
+		                                                     rdata->reachable_time_ms);
+	}
+
+	if (changed & NM_NDISC_CONFIG_RETRANS_TIMER) {
+		nm_platform_sysctl_ip_neigh_set_ipv6_retrans_time (nm_device_get_platform (self),
+		                                                   nm_device_get_ip_iface (self),
+		                                                   rdata->retrans_timer_ms);
+	}
+
 	if (changed & NM_NDISC_CONFIG_MTU) {
 		if (priv->ip6_mtu != rdata->mtu) {
 			_LOGD (LOGD_DEVICE, "mtu: set IPv6 MTU to %u", (guint) rdata->mtu);
diff --git a/src/ndisc/nm-lndp-ndisc.c b/src/ndisc/nm-lndp-ndisc.c
index 5643c19286..9352a75352 100644
--- a/src/ndisc/nm-lndp-ndisc.c
+++ b/src/ndisc/nm-lndp-ndisc.c
@@ -116,6 +116,7 @@ receive_ra (struct ndp *ndp, struct ndp_msg *msg, gpointer user_data)
 	gint32 now = nm_utils_get_monotonic_timestamp_s ();
 	int offset;
 	int hop_limit;
+	guint32 val;
 
 	/* Router discovery is subject to the following RFC documents:
 	 *
@@ -294,6 +295,18 @@ receive_ra (struct ndp *ndp, struct ndp_msg *msg, gpointer user_data)
 		changed |= NM_NDISC_CONFIG_HOP_LIMIT;
 	}
 
+	val = ndp_msgra_reachable_time (msgra);
+	if (val && rdata->public.reachable_time_ms != val) {
+		rdata->public.reachable_time_ms = val;
+		changed |= NM_NDISC_CONFIG_REACHABLE_TIME;
+	}
+
+	val = ndp_msgra_retransmit_time (msgra);
+	if (val && rdata->public.retrans_timer_ms != val) {
+		rdata->public.retrans_timer_ms = val;
+		changed |= NM_NDISC_CONFIG_RETRANS_TIMER;
+	}
+
 	/* MTU */
 	ndp_msg_opt_for_each_offset(offset, msg, NDP_MSG_OPT_MTU) {
 		guint32 mtu = ndp_msg_opt_mtu(msg, offset);
diff --git a/src/ndisc/nm-ndisc.c b/src/ndisc/nm-ndisc.c
index 1acf5ba9e6..a8fabb5634 100644
--- a/src/ndisc/nm-ndisc.c
+++ b/src/ndisc/nm-ndisc.c
@@ -1039,6 +1039,14 @@ _config_changed_log (NMNDisc *ndisc, NMNDiscConfigMap changed)
 	config_map_to_string (changed, changedstr);
 	_LOGD ("neighbor discovery configuration changed [%s]:", changedstr);
 	_LOGD ("  dhcp-level %s", dhcp_level_to_string (priv->rdata.public.dhcp_level));
+
+	if (rdata->public.hop_limit)
+		_LOGD ("  hop limit      : %d", rdata->public.hop_limit);
+	if (rdata->public.reachable_time_ms)
+		_LOGD ("  reachable time : %u", (guint) rdata->public.reachable_time_ms);
+	if (rdata->public.retrans_timer_ms)
+		_LOGD ("  retrans timer  : %u", (guint) rdata->public.retrans_timer_ms);
+
 	for (i = 0; i < rdata->gateways->len; i++) {
 		NMNDiscGateway *gateway = &g_array_index (rdata->gateways, NMNDiscGateway, i);
 
diff --git a/src/ndisc/nm-ndisc.h b/src/ndisc/nm-ndisc.h
index 766d4ab9e4..8e07ca41de 100644
--- a/src/ndisc/nm-ndisc.h
+++ b/src/ndisc/nm-ndisc.h
@@ -112,6 +112,8 @@ typedef enum {
 	NM_NDISC_CONFIG_DNS_DOMAINS                         = 1 << 5,
 	NM_NDISC_CONFIG_HOP_LIMIT                           = 1 << 6,
 	NM_NDISC_CONFIG_MTU                                 = 1 << 7,
+	NM_NDISC_CONFIG_REACHABLE_TIME                      = 1 << 8,
+	NM_NDISC_CONFIG_RETRANS_TIMER                       = 1 << 9,
 } NMNDiscConfigMap;
 
 typedef enum {
@@ -137,6 +139,8 @@ typedef struct {
 	NMNDiscDHCPLevel dhcp_level;
 	guint32 mtu;
 	int hop_limit;
+	guint32 reachable_time_ms;
+	guint32 retrans_timer_ms;
 
 	guint gateways_n;
 	guint addresses_n;
diff --git a/src/nm-iface-helper.c b/src/nm-iface-helper.c
index 239b46a140..f93f3470d5 100644
--- a/src/nm-iface-helper.c
+++ b/src/nm-iface-helper.c
@@ -220,6 +220,18 @@ ndisc_config_changed (NMNDisc *ndisc, const NMNDiscData *rdata, guint changed_in
 	if (changed & NM_NDISC_CONFIG_HOP_LIMIT)
 		nm_platform_sysctl_ip_conf_set_ipv6_hop_limit_safe (NM_PLATFORM_GET, global_opt.ifname, rdata->hop_limit);
 
+	if (changed & NM_NDISC_CONFIG_REACHABLE_TIME) {
+		nm_platform_sysctl_ip_neigh_set_ipv6_reachable_time (NM_PLATFORM_GET,
+		                                                     global_opt.ifname,
+		                                                     rdata->reachable_time_ms);
+	}
+
+	if (changed & NM_NDISC_CONFIG_RETRANS_TIMER) {
+		nm_platform_sysctl_ip_neigh_set_ipv6_retrans_time (NM_PLATFORM_GET,
+		                                                   global_opt.ifname,
+		                                                   rdata->retrans_timer_ms);
+	}
+
 	if (changed & NM_NDISC_CONFIG_MTU) {
 		nm_platform_sysctl_ip_conf_set_int64 (NM_PLATFORM_GET,
 		                                      AF_INET6,
diff --git a/src/platform/nm-platform.c b/src/platform/nm-platform.c
index 6ead15ed35..0a7acba9ab 100644
--- a/src/platform/nm-platform.c
+++ b/src/platform/nm-platform.c
@@ -610,6 +610,54 @@ nm_platform_sysctl_ip_conf_set_ipv6_hop_limit_safe (NMPlatform *self,
 	return TRUE;
 }
 
+gboolean
+nm_platform_sysctl_ip_neigh_set_ipv6_reachable_time (NMPlatform *self,
+                                                     const char *iface,
+                                                     guint value_ms)
+{
+	char path[NM_UTILS_SYSCTL_IP_CONF_PATH_BUFSIZE];
+	char str[128];
+	guint clamped;
+
+	_CHECK_SELF (self, klass, FALSE);
+
+	if (!value_ms)
+		return TRUE;
+
+	/* RFC 4861 says the value can't be greater than one hour.
+	 * Also use a reasonable lower threshold. */
+	clamped = NM_CLAMP (value_ms, 100, 3600000);
+	nm_sprintf_buf (path, "/proc/sys/net/ipv6/neigh/%s/base_reachable_time_ms", iface);
+	nm_sprintf_buf (str, "%u", clamped);
+	if (!nm_platform_sysctl_set (self, NMP_SYSCTL_PATHID_ABSOLUTE (path), str))
+		return FALSE;
+
+	/* Set stale time in the same way as kernel */
+	nm_sprintf_buf (path, "/proc/sys/net/ipv6/neigh/%s/gc_stale_time", iface);
+	nm_sprintf_buf (str, "%u", clamped * 3 / 1000);
+
+	return nm_platform_sysctl_set (self, NMP_SYSCTL_PATHID_ABSOLUTE (path), str);
+}
+
+gboolean
+nm_platform_sysctl_ip_neigh_set_ipv6_retrans_time (NMPlatform *self,
+                                                   const char *iface,
+                                                   guint value_ms)
+{
+	char path[NM_UTILS_SYSCTL_IP_CONF_PATH_BUFSIZE];
+	char str[128];
+
+	_CHECK_SELF (self, klass, FALSE);
+
+	if (!value_ms)
+		return TRUE;
+
+	nm_sprintf_buf (path, "/proc/sys/net/ipv6/neigh/%s/retrans_time_ms", iface);
+	nm_sprintf_buf (str, "%u", NM_CLAMP (value_ms, 10, 3600000));
+
+	return nm_platform_sysctl_set (self, NMP_SYSCTL_PATHID_ABSOLUTE (path), str);
+}
+
 /**
  * nm_platform_sysctl_get:
  * @self: platform instance
diff --git a/src/platform/nm-platform.h b/src/platform/nm-platform.h
index 248eca44f9..44733809f0 100644
--- a/src/platform/nm-platform.h
+++ b/src/platform/nm-platform.h
@@ -1353,6 +1353,12 @@ gboolean nm_platform_sysctl_ip_conf_set_int64 (NMPlatform *self,
 gboolean nm_platform_sysctl_ip_conf_set_ipv6_hop_limit_safe (NMPlatform *self,
                                                              const char *iface,
                                                              int value);
+gboolean nm_platform_sysctl_ip_neigh_set_ipv6_reachable_time (NMPlatform *self,
+                                                              const char *iface,
+                                                              guint value_ms);
+gboolean nm_platform_sysctl_ip_neigh_set_ipv6_retrans_time (NMPlatform *self,
+                                                            const char *iface,
+                                                            guint value_ms);
 int nm_platform_sysctl_ip_conf_get_rp_filter_ipv4 (NMPlatform *platform,
                                                    const char *iface,
                                                    gboolean consider_all,