network: Add support to advertie ipv6 route

Implements https://tools.ietf.org/html/rfc4191

cat veth99.network
```
[Match]
Name=veth99

[Network]
DHCP=no
IPv6PrefixDelegation=yes
Address=2001:db8:0:1::1/64

[IPv6Prefix]
Prefix=2001:db8:0:1::4/64

[IPv6RoutePrefix]
Route=2001:db0:fff::/48

```
Wireshark

```
Frame 481: 142 bytes on wire (1136 bits), 142 bytes captured (1136 bits) on interface 0
Ethernet II, Src: 1e:04:f8:b8:2f:d4 (1e:04:f8:b8:2f:d4), Dst: IPv6mcast_01 (33:33:00:00:00:01)
Internet Protocol Version 6, Src: fe80::1c04:f8ff:feb8:2fd4, Dst: ff02::1
Internet Control Message Protocol v6
    Type: Router Advertisement (134)
    Code: 0
    Checksum: 0xec77 [correct]
    [Checksum Status: Good]
    Cur hop limit: 0
    Flags: 0x00, Prf (Default Router Preference): Medium
    Router lifetime (s): 0
    Reachable time (ms): 0
    Retrans timer (ms): 0
    ICMPv6 Option (Source link-layer address : 1e:04:f8:b8:2f:d4)
        Type: Source link-layer address (1)
        Length: 1 (8 bytes)
        Link-layer address: 1e:04:f8:b8:2f:d4 (1e:04:f8:b8:2f:d4)
    ICMPv6 Option (MTU : 1500)
        Type: MTU (5)
        Length: 1 (8 bytes)
        Reserved
        MTU: 1500
    ICMPv6 Option (Prefix information : 2001:db8:0:1::4/64)
        Type: Prefix information (3)
        Length: 4 (32 bytes)
        Prefix Length: 64
        Flag: 0xc0, On-link flag(L), Autonomous address-configuration flag(A)
        Valid Lifetime: 2592000
        Preferred Lifetime: 604800
        Reserved
        Prefix: 2001:db8:0:1::4
    ICMPv6 Option (Route Information : Medium 2001:db0:fff::/48)
        Type: Route Information (24)
        Length: 3 (24 bytes)
        Prefix Length: 48
        Flag: 0x00, Route Preference: Medium
            ...0 0... = Route Preference: Medium (0)
            000. .000 = Reserved: 0
        Route Lifetime: 604800
        Prefix: 2001:db0:fff::
```

src/network/networkd-network-gperf.gperf

@@ -223,6 +223,8 @@ IPv6Prefix.OnLink,                      config_parse_prefix_flags,
 IPv6Prefix.AddressAutoconfiguration,    config_parse_prefix_flags,                       0,                             0
 IPv6Prefix.ValidLifetimeSec,            config_parse_prefix_lifetime,                    0,                             0
 IPv6Prefix.PreferredLifetimeSec,        config_parse_prefix_lifetime,                    0,                             0
+IPv6RoutePrefix.Route,                  config_parse_route_prefix,                       0,                             0
+IPv6RoutePrefix.LifetimeSec,            config_parse_route_prefix_lifetime,              0,                             0
 CAN.BitRate,                            config_parse_si_size,                            0,                             offsetof(Network, can_bitrate)
 CAN.SamplePoint,                        config_parse_permille,                           0,                             offsetof(Network, can_sample_point)
 CAN.RestartSec,                         config_parse_sec,                                0,                             offsetof(Network, can_restart_us)

src/network/networkd-network.c

@@ -458,6 +458,7 @@ int network_load_one(Manager *manager, const char *filename) {
                               "BridgeVLAN\0"
                               "IPv6PrefixDelegation\0"
                               "IPv6Prefix\0"
+                              "IPv6RoutePrefix\0"
                               "CAN\0",
                               config_item_perf_lookup, network_network_gperf_lookup,
                               CONFIG_PARSE_WARN, network);

src/network/networkd-network.h

@@ -221,6 +221,7 @@ struct Network {
         LIST_HEAD(Neighbor, neighbors);
         LIST_HEAD(AddressLabel, address_labels);
         LIST_HEAD(Prefix, static_prefixes);
+        LIST_HEAD(Prefix, static_route_prefixes);
         LIST_HEAD(RoutingPolicyRule, rules);
 
         unsigned n_static_addresses;
@@ -230,6 +231,7 @@ struct Network {
         unsigned n_neighbors;
         unsigned n_address_labels;
         unsigned n_static_prefixes;
+        unsigned n_static_route_prefixes;
         unsigned n_rules;
 
         Hashmap *addresses_by_section;
@@ -238,6 +240,7 @@ struct Network {
         Hashmap *neighbors_by_section;
         Hashmap *address_labels_by_section;
         Hashmap *prefixes_by_section;
+        Hashmap *route_prefixes_by_section;
         Hashmap *rules_by_section;
 
         /* All kinds of DNS configuration */

src/network/networkd-radv.c

@@ -101,16 +101,100 @@ static int prefix_new_static(Network *network, const char *filename,
         return 0;
 }
 
+int route_prefix_new(Prefix **ret) {
+        _cleanup_(prefix_freep) Prefix *prefix = NULL;
+
+        prefix = new0(Prefix, 1);
+        if (!prefix)
+                return -ENOMEM;
+
+        if (sd_radv_route_prefix_new(&prefix->radv_route_prefix) < 0)
+                return -ENOMEM;
+
+        *ret = TAKE_PTR(prefix);
+
+        return 0;
+}
+
+void route_prefix_free(Prefix *prefix) {
+        if (!prefix)
+                return;
+
+        if (prefix->network) {
+                LIST_REMOVE(prefixes, prefix->network->static_route_prefixes, prefix);
+                assert(prefix->network->n_static_route_prefixes > 0);
+                prefix->network->n_static_route_prefixes--;
+
+                if (prefix->section)
+                        hashmap_remove(prefix->network->route_prefixes_by_section,
+                                       prefix->section);
+        }
+
+        network_config_section_free(prefix->section);
+
+        free(prefix);
+}
+
+static int route_prefix_new_static(Network *network, const char *filename,
+                                   unsigned section_line, Prefix **ret) {
+        _cleanup_(network_config_section_freep) NetworkConfigSection *n = NULL;
+        _cleanup_(prefix_freep) Prefix *prefix = NULL;
+        int r;
+
+        assert(network);
+        assert(ret);
+        assert(!!filename == (section_line > 0));
+
+        if (filename) {
+                r = network_config_section_new(filename, section_line, &n);
+                if (r < 0)
+                        return r;
+
+                if (section_line) {
+                        prefix = hashmap_get(network->route_prefixes_by_section, n);
+                        if (prefix) {
+                                *ret = TAKE_PTR(prefix);
+
+                                return 0;
+                        }
+                }
+        }
+
+        r = route_prefix_new(&prefix);
+        if (r < 0)
+                return r;
+
+        prefix->network = network;
+        LIST_APPEND(prefixes, network->static_route_prefixes, prefix);
+        network->n_static_route_prefixes++;
+
+        if (filename) {
+                prefix->section = TAKE_PTR(n);
+
+                r = hashmap_ensure_allocated(&network->route_prefixes_by_section, &network_config_hash_ops);
+                if (r < 0)
+                        return r;
+
+                r = hashmap_put(network->route_prefixes_by_section, prefix->section, prefix);
+                if (r < 0)
+                        return r;
+        }
+
+        *ret = TAKE_PTR(prefix);
+
+        return 0;
+}
+
 int config_parse_prefix(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) {
+                        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_(prefix_free_or_set_invalidp) Prefix *p = NULL;
@@ -234,6 +318,90 @@ int config_parse_prefix_lifetime(const char *unit,
         return 0;
 }
 
+int config_parse_route_prefix(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_(prefix_free_or_set_invalidp) Prefix *p = NULL;
+        uint8_t prefixlen = 64;
+        union in_addr_union in6addr;
+        int r;
+
+        assert(filename);
+        assert(section);
+        assert(lvalue);
+        assert(rvalue);
+        assert(data);
+
+        r = route_prefix_new_static(network, filename, section_line, &p);
+        if (r < 0)
+                return r;
+
+        r = in_addr_prefix_from_string(rvalue, AF_INET6, &in6addr, &prefixlen);
+        if (r < 0) {
+                log_syntax(unit, LOG_ERR, filename, line, r, "Route prefix is invalid, ignoring assignment: %s", rvalue);
+                return 0;
+        }
+
+        if (sd_radv_prefix_set_route_prefix(p->radv_route_prefix, &in6addr.in6, prefixlen) < 0)
+                return -EADDRNOTAVAIL;
+
+        log_syntax(unit, LOG_INFO, filename, line, r, "Found route prefix %s", rvalue);
+
+        p = NULL;
+
+        return 0;
+}
+
+int config_parse_route_prefix_lifetime(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_(prefix_free_or_set_invalidp) Prefix *p = NULL;
+        usec_t usec;
+        int r;
+
+        assert(filename);
+        assert(section);
+        assert(lvalue);
+        assert(rvalue);
+        assert(data);
+
+        r = route_prefix_new_static(network, filename, section_line, &p);
+        if (r < 0)
+                return r;
+
+        r = parse_sec(rvalue, &usec);
+        if (r < 0) {
+                log_syntax(unit, LOG_ERR, filename, line, r, "Roure lifetime is invalid, ignoring assignment: %s", rvalue);
+                return 0;
+        }
+
+        /* a value of 0xffffffff represents infinity */
+        r = sd_radv_route_prefix_set_lifetime(p->radv_route_prefix, DIV_ROUND_UP(usec, USEC_PER_SEC));
+        if (r < 0)
+                return r;
+
+        p = NULL;
+
+        return 0;
+}
+
 static int radv_get_ip6dns(Network *network, struct in6_addr **dns,
                            size_t *n_dns) {
         _cleanup_free_ struct in6_addr *addresses = NULL;
@@ -438,6 +606,15 @@ int radv_configure(Link *link) {
                         if (r < 0)
                                 return r;
                 }
+
+                LIST_FOREACH(prefixes, p, link->network->static_route_prefixes) {
+                        r = sd_radv_add_route_prefix(link->radv, p->radv_route_prefix, false);
+                        if (r == -EEXIST)
+                                continue;
+                        if (r < 0)
+                                return r;
+                }
+
         }
 
         return radv_emit_dns(link);

src/network/networkd-radv.h

@@ -26,8 +26,10 @@ struct Prefix {
         NetworkConfigSection *section;
 
         sd_radv_prefix *radv_prefix;
+        sd_radv_route_prefix *radv_route_prefix;
 
         LIST_FIELDS(Prefix, prefixes);
+        LIST_FIELDS(Prefix, route_prefixes);
 };
 
 int prefix_new(Prefix **ret);
@@ -35,6 +37,11 @@ void prefix_free(Prefix *prefix);
 
 DEFINE_NETWORK_SECTION_FUNCTIONS(Prefix, prefix_free);
 
+int route_prefix_new(Prefix **ret);
+void route_prefix_free(Prefix *prefix);
+
+DEFINE_NETWORK_SECTION_FUNCTIONS(Prefix, route_prefix_free);
+
 int radv_emit_dns(Link *link);
 int radv_configure(Link *link);
 
@@ -48,3 +55,5 @@ CONFIG_PARSER_PROTOTYPE(config_parse_prefix_flags);
 CONFIG_PARSER_PROTOTYPE(config_parse_prefix_lifetime);
 CONFIG_PARSER_PROTOTYPE(config_parse_radv_dns);
 CONFIG_PARSER_PROTOTYPE(config_parse_radv_search_domains);
+CONFIG_PARSER_PROTOTYPE(config_parse_route_prefix);
+CONFIG_PARSER_PROTOTYPE(config_parse_route_prefix_lifetime);