Merge pull request #17551 from yuwata/radv-router-lifetime

network: about router lifetime

man/systemd.network.xml

@@ -2254,9 +2254,8 @@ IPv6Token=prefixstable:2002:da8:1::</programlisting></para>
       <varlistentry>
         <term><varname>RouterLifetimeSec=</varname></term>
 
-        <listitem><para>Takes a timespan. Configures the IPv6 router lifetime in seconds. If set,
+        <listitem><para>Takes a timespan. Configures the IPv6 router lifetime in seconds. When set to
-        this host also announces itself in Router Advertisements as an IPv6
+        0, the host is not acting as a router. Defaults to 30 minutes.</para>
-        router for the network link. When unset, the host is not acting as a router.</para>
         </listitem>
       </varlistentry>
 

src/libsystemd-network/sd-radv.c

@@ -466,14 +466,14 @@ _public_ int sd_radv_set_hop_limit(sd_radv *ra, uint8_t hop_limit) {
         return 0;
 }
 
-_public_ int sd_radv_set_router_lifetime(sd_radv *ra, uint32_t router_lifetime) {
+_public_ int sd_radv_set_router_lifetime(sd_radv *ra, uint16_t router_lifetime) {
         assert_return(ra, -EINVAL);
 
         if (ra->state != SD_RADV_STATE_IDLE)
                 return -EBUSY;
 
-        /* RFC 4191, Section 2.2, "...If the Router Lifetime is zero, the
+        /* RFC 4191, Section 2.2, "...If the Router Lifetime is zero, the preference value MUST be set
-           preference value MUST be set to (00) by the sender..." */
+         * to (00) by the sender..." */
         if (router_lifetime == 0 &&
             (ra->flags & (0x3 << 3)) != (SD_NDISC_PREFERENCE_MEDIUM << 3))
                 return -ETIME;
@@ -506,17 +506,20 @@ _public_ int sd_radv_set_other_information(sd_radv *ra, int other) {
 }
 
 _public_ int sd_radv_set_preference(sd_radv *ra, unsigned preference) {
-        int r = 0;
-
         assert_return(ra, -EINVAL);
         assert_return(IN_SET(preference,
                              SD_NDISC_PREFERENCE_LOW,
                              SD_NDISC_PREFERENCE_MEDIUM,
                              SD_NDISC_PREFERENCE_HIGH), -EINVAL);
 
+        /* RFC 4191, Section 2.2, "...If the Router Lifetime is zero, the preference value MUST be set
+         * to (00) by the sender..." */
+        if (ra->lifetime == 0 && preference != SD_NDISC_PREFERENCE_MEDIUM)
+                return -EINVAL;
+
         ra->flags = (ra->flags & ~(0x3 << 3)) | (preference << 3);
 
-        return r;
+        return 0;
 }
 
 _public_ int sd_radv_add_prefix(sd_radv *ra, sd_radv_prefix *p, int dynamic) {

src/network/networkd-network.c

@@ -379,6 +379,7 @@ int network_load_one(Manager *manager, OrderedHashmap **networks, const char *fi
                 .dhcp_server_emit_router = true,
                 .dhcp_server_emit_timezone = true,
 
+                .router_lifetime_usec = 30 * USEC_PER_MINUTE,
                 .router_emit_dns = true,
                 .router_emit_domains = true,
 

src/network/networkd-radv.c

@@ -641,6 +641,7 @@ static bool link_radv_enabled(Link *link) {
 }
 
 int radv_configure(Link *link) {
+        uint16_t router_lifetime;
         RoutePrefix *q;
         Prefix *p;
         int r;
@@ -675,16 +676,20 @@ int radv_configure(Link *link) {
         if (r < 0)
                 return r;
 
-        /* a value of 0xffffffff represents infinity, 0x0 means this host is
+        /* a value of UINT16_MAX represents infinity, 0x0 means this host is not a router */
-           not a router */
+        if (link->network->router_lifetime_usec == USEC_INFINITY)
-        r = sd_radv_set_router_lifetime(link->radv,
+                router_lifetime = UINT16_MAX;
-                                        DIV_ROUND_UP(link->network->router_lifetime_usec, USEC_PER_SEC));
+        else if (link->network->router_lifetime_usec > (UINT16_MAX - 1) * USEC_PER_SEC)
+                router_lifetime = UINT16_MAX - 1;
+        else
+                router_lifetime = DIV_ROUND_UP(link->network->router_lifetime_usec, USEC_PER_SEC);
+
+        r = sd_radv_set_router_lifetime(link->radv, router_lifetime);
         if (r < 0)
                 return r;
 
-        if (link->network->router_lifetime_usec > 0) {
+        if (router_lifetime > 0) {
-                r = sd_radv_set_preference(link->radv,
+                r = sd_radv_set_preference(link->radv, link->network->router_preference);
-                                           link->network->router_preference);
                 if (r < 0)
                         return r;
         }

src/systemd/sd-radv.h

@@ -56,7 +56,7 @@ int sd_radv_set_ifindex(sd_radv *ra, int interface_index);
 int sd_radv_set_mac(sd_radv *ra, const struct ether_addr *mac_addr);
 int sd_radv_set_mtu(sd_radv *ra, uint32_t mtu);
 int sd_radv_set_hop_limit(sd_radv *ra, uint8_t hop_limit);
-int sd_radv_set_router_lifetime(sd_radv *ra, uint32_t router_lifetime);
+int sd_radv_set_router_lifetime(sd_radv *ra, uint16_t router_lifetime);
 int sd_radv_set_managed_information(sd_radv *ra, int managed);
 int sd_radv_set_other_information(sd_radv *ra, int other);
 int sd_radv_set_preference(sd_radv *ra, unsigned preference);