networkd: make IPv6 route preference configurable (#5700)

The work supports route preference configurable.
i.e. able to set low, medium and high.

4 files changed, 43 insertions, 0 deletions

diff --git a/man/systemd.network.xml b/man/systemd.network.xml
index fdf7d5caaf..4b80578333 100644
--- a/man/systemd.network.xml
+++ b/man/systemd.network.xml
@@ -842,6 +842,16 @@
           </listitem>
         </varlistentry>
         <varlistentry>
+          <term><varname>IPv6Preference=</varname></term>
+          <listitem>
+            <para>Specifies the route preference as defined in <ulink
+            url="https://tools.ietf.org/html/rfc4191">RFC4191</ulink> for Router Discovery messages.
+            Which can be one of <literal>low</literal> the route has a lowest priority,
+            <literal>medium</literal> the route has a default priority or
+            <literal>high</literal> the route has a highest priority.</para>
+          </listitem>
+        </varlistentry>
+        <varlistentry>
           <term><varname>Scope=</varname></term>
           <listitem>
             <para>The scope of the route, which can be <literal>global</literal>,
diff --git a/src/network/networkd-network-gperf.gperf b/src/network/networkd-network-gperf.gperf
index abd921ee1a..3743113825 100644
--- a/src/network/networkd-network-gperf.gperf
+++ b/src/network/networkd-network-gperf.gperf
@@ -87,6 +87,7 @@ Route.Scope,                            config_parse_route_scope,
 Route.PreferredSource,                  config_parse_preferred_src,                     0,                             0
 Route.Table,                            config_parse_route_table,                       0,                             0
 Route.GatewayOnlink,                    config_parse_gateway_onlink,                    0,                             0
+Route.IPv6Preference,                   config_parse_ipv6_route_preference,             0,                             0
 DHCP.ClientIdentifier,                  config_parse_dhcp_client_identifier,            0,                             offsetof(Network, dhcp_client_identifier)
 DHCP.UseDNS,                            config_parse_bool,                              0,                             offsetof(Network, dhcp_use_dns)
 DHCP.UseNTP,                            config_parse_bool,                              0,                             offsetof(Network, dhcp_use_ntp)
diff --git a/src/network/networkd-route.c b/src/network/networkd-route.c
index e2a5c77ed1..56f831628c 100644
--- a/src/network/networkd-route.c
+++ b/src/network/networkd-route.c
@@ -17,6 +17,8 @@
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+#include <linux/icmpv6.h>
+
 #include "alloc-util.h"
 #include "conf-parser.h"
 #include "in-addr-util.h"
@@ -975,6 +977,35 @@ int config_parse_gateway_onlink(const char *unit,
                 n->flags |= RTNH_F_ONLINK;
         else
                 n->flags &= ~RTNH_F_ONLINK;
+        n = NULL;
+
+        return 0;
+}
+
+int config_parse_ipv6_route_preference(const char *unit,
+                                       const char *filename,
+                                       unsigned line,
+                                       const char *section,
+                                       unsigned section_line,
+                                       const char *lvalue,
+                                       int ltype,
+                                       const char *rvalue,
+                                       void *data,
+                                       void *userdata) {
+        Network *network = userdata;
+        _cleanup_route_free_ Route *n = NULL;
+        int r;
+
+        if (streq(rvalue, "low"))
+                n->pref = ICMPV6_ROUTER_PREF_LOW;
+        else if (streq(rvalue, "medium"))
+                n->pref = ICMPV6_ROUTER_PREF_MEDIUM;
+        else if (streq(rvalue, "high"))
+                n->pref = ICMPV6_ROUTER_PREF_HIGH;
+        else {
+                log_syntax(unit, LOG_ERR, filename, line, 0, "Unknown route preference: %s", rvalue);
+                return 0;
+        }
 
         n = NULL;
 
diff --git a/src/network/networkd-route.h b/src/network/networkd-route.h
index e2446b3e92..47ff6f28a0 100644
--- a/src/network/networkd-route.h
+++ b/src/network/networkd-route.h
@@ -76,3 +76,4 @@ int config_parse_route_priority(const char *unit, const char *filename, unsigned
 int config_parse_route_scope(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
 int config_parse_route_table(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
 int config_parse_gateway_onlink(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
+int config_parse_ipv6_route_preference(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);