network: DHCP server Add support to transmit SIP server

1. DHCP server trasmit
2. Client parses and saves in leases
Implements http://www.rfc-editor.org/rfc/rfc3361.txt

```
Frame 134: 348 bytes on wire (2784 bits), 348 bytes captured (2784 bits) on interface 0
Ethernet II, Src: 42:65:85:d6:4e:32 (42:65:85:d6:4e:32), Dst: 1e:04:f8:b8:2f:d4 (1e:04:f8:b8:2f:d4)
Internet Protocol Version 4, Src: 192.168.5.1, Dst: 192.168.5.11
User Datagram Protocol, Src Port: 67, Dst Port: 68
Dynamic Host Configuration Protocol (ACK)
    Message type: Boot Reply (2)
    Hardware type: Ethernet (0x01)
    Hardware address length: 6
    Hops: 0
    Transaction ID: 0x7cc87cb4
    Seconds elapsed: 0
    Bootp flags: 0x0000 (Unicast)
    Client IP address: 0.0.0.0
    Your (client) IP address: 192.168.5.11
    Next server IP address: 0.0.0.0
    Relay agent IP address: 0.0.0.0
    Client MAC address: 1e:04:f8:b8:2f:d4 (1e:04:f8:b8:2f:d4)
    Client hardware address padding: 00000000000000000000
    Server host name not given
    Boot file name not given
    Magic cookie: DHCP
    Option: (53) DHCP Message Type (ACK)
        Length: 1
        DHCP: ACK (5)
    Option: (51) IP Address Lease Time
        Length: 4
        IP Address Lease Time: (3600s) 1 hour
    Option: (1) Subnet Mask (255.255.255.0)
        Length: 4
        Subnet Mask: 255.255.255.0
    Option: (3) Router
        Length: 4
        Router: 192.168.5.1
    Option: (6) Domain Name Server
        Length: 4
        Domain Name Server: 192.168.5.1
    Option: (42) Network Time Protocol Servers
        Length: 4
        Network Time Protocol Server: 192.168.1.1
    Option: (120) SIP Servers <=====here
        Length: 9
        SIP Server Encoding: IPv4 Address (1)
        SIP Server Address: 192.168.1.1
        SIP Server Address: 192.168.5.2
    Option: (101) TCode
        Length: 13
        TZ TCode: Europe/Berlin
    Option: (54) DHCP Server Identifier (192.168.5.1)
        Length: 4
        DHCP Server Identifier: 192.168.5.1
    Option: (255) End
        Option End: 255
```

```
cat /run/systemd/netif/state                                                                                                   ✔  ⚡  3148  16:40:51
OPER_STATE=routable
CARRIER_STATE=carrier
ADDRESS_STATE=routable
DNS=192.168.94.2 192.168.5.1
NTP=192.168.5.1
SIP=192.168.1.1 192.168.5.2

```

aa

5 files changed, 118 insertions, 2 deletions

diff --git a/src/libsystemd-network/dhcp-lease-internal.h b/src/libsystemd-network/dhcp-lease-internal.h
index 122042ab58..a2d0f8bd5e 100644
--- a/src/libsystemd-network/dhcp-lease-internal.h
+++ b/src/libsystemd-network/dhcp-lease-internal.h
@@ -58,6 +58,9 @@ struct sd_dhcp_lease {
         struct in_addr *ntp;
         size_t ntp_size;
 
+        struct in_addr *sip;
+        size_t sip_size;
+
         struct sd_dhcp_route *static_route;
         size_t static_route_size, static_route_allocated;
 
diff --git a/src/libsystemd-network/dhcp-option.c b/src/libsystemd-network/dhcp-option.c
index 05386b615d..d2f1f5d806 100644
--- a/src/libsystemd-network/dhcp-option.c
+++ b/src/libsystemd-network/dhcp-option.c
@@ -65,6 +65,18 @@ static int option_append(uint8_t options[], size_t size, size_t *offset,
 
                 break;
         }
+        case SD_DHCP_OPTION_SIP_SERVER:
+                if (*offset + 3 + optlen > size)
+                        return -ENOBUFS;
+
+                options[*offset] = code;
+                options[*offset + 1] = optlen + 1;
+                options[*offset + 2] = 1;
+
+                memcpy_safe(&options[*offset + 3], optval, optlen);
+                *offset += 3 + optlen;
+
+                break;
         default:
                 if (*offset + 2 + optlen > size)
                         return -ENOBUFS;
diff --git a/src/libsystemd-network/dhcp-server-internal.h b/src/libsystemd-network/dhcp-server-internal.h
index 256006ebeb..0a64082cd1 100644
--- a/src/libsystemd-network/dhcp-server-internal.h
+++ b/src/libsystemd-network/dhcp-server-internal.h
@@ -45,8 +45,8 @@ struct sd_dhcp_server {
 
         char *timezone;
 
-        struct in_addr *ntp, *dns;
-        unsigned n_ntp, n_dns;
+        struct in_addr *ntp, *dns, *sip;
+        unsigned n_ntp, n_dns, n_sip;
 
         bool emit_router;
 
diff --git a/src/libsystemd-network/sd-dhcp-lease.c b/src/libsystemd-network/sd-dhcp-lease.c
index 17b2bb7aa4..e360b725ac 100644
--- a/src/libsystemd-network/sd-dhcp-lease.c
+++ b/src/libsystemd-network/sd-dhcp-lease.c
@@ -120,6 +120,17 @@ int sd_dhcp_lease_get_ntp(sd_dhcp_lease *lease, const struct in_addr **addr) {
         return (int) lease->ntp_size;
 }
 
+int sd_dhcp_lease_get_sip(sd_dhcp_lease *lease, const struct in_addr **addr) {
+        assert_return(lease, -EINVAL);
+        assert_return(addr, -EINVAL);
+
+        if (lease->sip_size <= 0)
+                return -ENODATA;
+
+        *addr = lease->sip;
+        return (int) lease->sip_size;
+}
+
 int sd_dhcp_lease_get_domainname(sd_dhcp_lease *lease, const char **domainname) {
         assert_return(lease, -EINVAL);
         assert_return(domainname, -EINVAL);
@@ -269,6 +280,7 @@ static sd_dhcp_lease *dhcp_lease_free(sd_dhcp_lease *lease) {
         free(lease->domainname);
         free(lease->dns);
         free(lease->ntp);
+        free(lease->sip);
         free(lease->static_route);
         free(lease->client_id);
         free(lease->vendor_specific);
@@ -402,6 +414,36 @@ static int lease_parse_in_addrs(const uint8_t *option, size_t len, struct in_add
         return 0;
 }
 
+static int lease_parse_sip_server(const uint8_t *option, size_t len, struct in_addr **ret, size_t *n_ret) {
+        assert(option);
+        assert(ret);
+        assert(n_ret);
+
+        if (len <= 0) {
+                *ret = mfree(*ret);
+                *n_ret = 0;
+        } else {
+                size_t n_addresses;
+                struct in_addr *addresses;
+                int l = len - 1;
+
+                if (l % 4 != 0)
+                        return -EINVAL;
+
+                n_addresses = l / 4;
+
+                addresses = newdup(struct in_addr, option + 1, n_addresses);
+                if (!addresses)
+                        return -ENOMEM;
+
+                free(*ret);
+                *ret = addresses;
+                *n_ret = n_addresses;
+        }
+
+        return 0;
+}
+
 static int lease_parse_routes(
                 const uint8_t *option, size_t len,
                 struct sd_dhcp_route **routes, size_t *routes_size, size_t *routes_allocated) {
@@ -555,6 +597,12 @@ int dhcp_lease_parse_options(uint8_t code, uint8_t len, const void *option, void
                         log_debug_errno(r, "Failed to parse NTP server, ignoring: %m");
                 break;
 
+        case SD_DHCP_OPTION_SIP_SERVER:
+                r = lease_parse_sip_server(option, len, &lease->sip, &lease->sip_size);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse SIP server, ignoring: %m");
+                break;
+
         case SD_DHCP_OPTION_STATIC_ROUTE:
                 r = lease_parse_routes(option, len, &lease->static_route, &lease->static_route_size, &lease->static_route_allocated);
                 if (r < 0)
@@ -893,6 +941,13 @@ int dhcp_lease_save(sd_dhcp_lease *lease, const char *lease_file) {
                 fputc('\n', f);
         }
 
+        r = sd_dhcp_lease_get_sip(lease, &addresses);
+        if (r > 0) {
+                fputs("SIP=", f);
+                serialize_in_addrs(f, addresses, r, false, NULL);
+                fputc('\n', f);
+        }
+
         r = sd_dhcp_lease_get_domainname(lease, &string);
         if (r >= 0)
                 fprintf(f, "DOMAINNAME=%s\n", string);
@@ -983,6 +1038,7 @@ int dhcp_lease_load(sd_dhcp_lease **ret, const char *lease_file) {
                 *broadcast = NULL,
                 *dns = NULL,
                 *ntp = NULL,
+                *sip = NULL,
                 *mtu = NULL,
                 *routes = NULL,
                 *domains = NULL,
@@ -1011,6 +1067,7 @@ int dhcp_lease_load(sd_dhcp_lease **ret, const char *lease_file) {
                            "BROADCAST", &broadcast,
                            "DNS", &dns,
                            "NTP", &ntp,
+                           "SIP", &sip,
                            "MTU", &mtu,
                            "DOMAINNAME", &lease->domainname,
                            "HOSTNAME", &lease->hostname,
@@ -1115,6 +1172,14 @@ int dhcp_lease_load(sd_dhcp_lease **ret, const char *lease_file) {
                         lease->ntp_size = r;
         }
 
+        if (sip) {
+                r = deserialize_in_addrs(&lease->sip, sip);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to deserialize SIP servers %s, ignoring: %m", ntp);
+                else
+                        lease->ntp_size = r;
+        }
+
         if (mtu) {
                 r = safe_atou16(mtu, &lease->mtu);
                 if (r < 0)
diff --git a/src/libsystemd-network/sd-dhcp-server.c b/src/libsystemd-network/sd-dhcp-server.c
index 7cb44d1fdf..13f104f9ef 100644
--- a/src/libsystemd-network/sd-dhcp-server.c
+++ b/src/libsystemd-network/sd-dhcp-server.c
@@ -139,6 +139,7 @@ static sd_dhcp_server *dhcp_server_free(sd_dhcp_server *server) {
         free(server->timezone);
         free(server->dns);
         free(server->ntp);
+        free(server->sip);
 
         hashmap_free(server->leases_by_client_id);
 
@@ -498,6 +499,15 @@ static int server_send_ack(sd_dhcp_server *server, DHCPRequest *req,
                         return r;
         }
 
+        if (server->n_sip > 0) {
+                r = dhcp_option_append(
+                                &packet->dhcp, req->max_optlen, &offset, 0,
+                                SD_DHCP_OPTION_SIP_SERVER,
+                                sizeof(struct in_addr) * server->n_sip, server->sip);
+                if (r < 0)
+                        return r;
+        }
+
         if (server->timezone) {
                 r = dhcp_option_append(
                                 &packet->dhcp, req->max_optlen, &offset, 0,
@@ -1124,6 +1134,32 @@ int sd_dhcp_server_set_ntp(sd_dhcp_server *server, const struct in_addr ntp[], u
         return 1;
 }
 
+int sd_dhcp_server_set_sip(sd_dhcp_server *server, const struct in_addr sip[], unsigned n) {
+        assert_return(server, -EINVAL);
+        assert_return(sip || n <= 0, -EINVAL);
+
+        if (server->n_sip == n &&
+            memcmp(server->sip, sip, sizeof(struct in_addr) * n) == 0)
+                return 0;
+
+        if (n <= 0) {
+                server->sip = mfree(server->sip);
+                server->n_sip = 0;
+        } else {
+                struct in_addr *c;
+
+                c = newdup(struct in_addr, sip, n);
+                if (!c)
+                        return -ENOMEM;
+
+                free(server->sip);
+                server->sip = c;
+                server->n_sip = n;
+        }
+
+        return 1;
+}
+
 int sd_dhcp_server_set_emit_router(sd_dhcp_server *server, int enabled) {
         assert_return(server, -EINVAL);