networkd: Add support for ERSPAN tunnel

Please see: https://patchwork.ozlabs.org/patch/800327/
```
[NetDev]
Name=erspan-test
Kind=erspan

[Tunnel]
Independent=true
ERSPANIndex=123
Local = 172.16.1.200
Remote = 172.16.1.100
Key=101
SerializeTunneledPackets=true
```

src/network/netdev/netdev-gperf.gperf

@@ -71,6 +71,8 @@ Tunnel.FOUDestinationPort,         config_parse_ip_port,                 0,
 Tunnel.FOUSourcePort,              config_parse_ip_port,                 0,                             offsetof(Tunnel, encap_src_port)
 Tunnel.Encapsulation,              config_parse_fou_encap_type,          0,                             offsetof(Tunnel, fou_encap_type)
 Tunnel.IPv6RapidDeploymentPrefix,  config_parse_6rd_prefix,              0,                             0
+Tunnel.ERSPANIndex,                config_parse_uint32,                  0,                             offsetof(Tunnel, erspan_index)
+Tunnel.SerializeTunneledPackets,   config_parse_tristate,                0,                             offsetof(Tunnel, erspan_sequence)
 FooOverUDP.Protocol,               config_parse_uint8,                   0,                             offsetof(FouTunnel, fou_protocol)
 FooOverUDP.Encapsulation,          config_parse_fou_encap_type,          0,                             offsetof(FouTunnel, fou_encap_type)
 FooOverUDP.Port,                   config_parse_ip_port,                 0,                             offsetof(FouTunnel, port)

src/network/netdev/netdev.c

@@ -64,6 +64,7 @@ const NetDevVTable * const netdev_vtable[_NETDEV_KIND_MAX] = {
         [NETDEV_KIND_WIREGUARD] = &wireguard_vtable,
         [NETDEV_KIND_NETDEVSIM] = &netdevsim_vtable,
         [NETDEV_KIND_FOU] = &foutnl_vtable,
+        [NETDEV_KIND_ERSPAN] = &erspan_vtable,
 };
 
 static const char* const netdev_kind_table[_NETDEV_KIND_MAX] = {
@@ -94,6 +95,7 @@ static const char* const netdev_kind_table[_NETDEV_KIND_MAX] = {
         [NETDEV_KIND_WIREGUARD] = "wireguard",
         [NETDEV_KIND_NETDEVSIM] = "netdevsim",
         [NETDEV_KIND_FOU] = "fou",
+        [NETDEV_KIND_ERSPAN] = "erspan",
 };
 
 DEFINE_STRING_TABLE_LOOKUP(netdev_kind, NetDevKind);

src/network/netdev/netdev.h

@@ -45,6 +45,7 @@ typedef enum NetDevKind {
         NETDEV_KIND_WIREGUARD,
         NETDEV_KIND_NETDEVSIM,
         NETDEV_KIND_FOU,
+        NETDEV_KIND_ERSPAN,
         _NETDEV_KIND_MAX,
         _NETDEV_KIND_INVALID = -1
 } NetDevKind;

src/network/netdev/tunnel.c

@@ -173,6 +173,77 @@ static int netdev_gre_fill_message_create(NetDev *netdev, Link *link, sd_netlink
         return r;
 }
 
+static int netdev_erspan_fill_message_create(NetDev *netdev, Link *link, sd_netlink_message *m) {
+        uint32_t ikey = 0;
+        uint32_t okey = 0;
+        uint16_t iflags = 0;
+        uint16_t oflags = 0;
+        Tunnel *t;
+        int r;
+
+        assert(netdev);
+
+        t = ERSPAN(netdev);
+
+        assert(t);
+        assert(IN_SET(t->family, AF_INET, AF_UNSPEC));
+        assert(m);
+
+        r = sd_netlink_message_append_u32(m, IFLA_GRE_ERSPAN_INDEX, t->erspan_index);
+        if (r < 0)
+                return log_netdev_error_errno(netdev, r, "Could not append IFLA_GRE_ERSPAN_INDEX attribute: %m");
+
+        if (t->key != 0) {
+                ikey = okey = htobe32(t->key);
+                iflags |= GRE_KEY;
+                oflags |= GRE_KEY;
+        }
+
+        if (t->ikey != 0) {
+                ikey = htobe32(t->ikey);
+                iflags |= GRE_KEY;
+        }
+
+        if (t->okey != 0) {
+                okey = htobe32(t->okey);
+                oflags |= GRE_KEY;
+        }
+
+        if (t->erspan_sequence > 0) {
+                iflags |= GRE_SEQ;
+                oflags |= GRE_SEQ;
+        } else if (t->erspan_sequence == 0) {
+                iflags &= ~GRE_SEQ;
+                oflags &= ~GRE_SEQ;
+        }
+
+        r = sd_netlink_message_append_u32(m, IFLA_GRE_IKEY, ikey);
+        if (r < 0)
+                return log_netdev_error_errno(netdev, r, "Could not append IFLA_GRE_IKEY attribute: %m");
+
+        r = sd_netlink_message_append_u32(m, IFLA_GRE_OKEY, okey);
+        if (r < 0)
+                return log_netdev_error_errno(netdev, r, "Could not append IFLA_GRE_OKEY attribute: %m");
+
+        r = sd_netlink_message_append_u16(m, IFLA_GRE_IFLAGS, iflags);
+        if (r < 0)
+                return log_netdev_error_errno(netdev, r, "Could not append IFLA_GRE_IFLAGS attribute: %m");
+
+        r = sd_netlink_message_append_u16(m, IFLA_GRE_OFLAGS, oflags);
+        if (r < 0)
+                return log_netdev_error_errno(netdev, r, "Could not append IFLA_GRE_OFLAGS, attribute: %m");
+
+        r = sd_netlink_message_append_in_addr(m, IFLA_GRE_LOCAL, &t->local.in);
+        if (r < 0)
+                return log_netdev_error_errno(netdev, r, "Could not append IFLA_GRE_LOCAL attribute: %m");
+
+        r = sd_netlink_message_append_in_addr(m, IFLA_GRE_REMOTE, &t->remote.in);
+        if (r < 0)
+                log_netdev_error_errno(netdev, r, "Could not append IFLA_GRE_REMOTE attribute: %m");
+
+        return r;
+}
+
 static int netdev_ip6gre_fill_message_create(NetDev *netdev, Link *link, sd_netlink_message *m) {
         Tunnel *t;
         int r;
@@ -415,6 +486,9 @@ static int netdev_tunnel_verify(NetDev *netdev, const char *filename) {
         case NETDEV_KIND_IP6TNL:
                 t = IP6TNL(netdev);
                 break;
+        case NETDEV_KIND_ERSPAN:
+                t = ERSPAN(netdev);
+                break;
         default:
                 assert_not_reached("Invalid tunnel kind");
         }
@@ -427,10 +501,10 @@ static int netdev_tunnel_verify(NetDev *netdev, const char *filename) {
                 return -EINVAL;
         }
 
-        if (IN_SET(netdev->kind, NETDEV_KIND_VTI, NETDEV_KIND_IPIP, NETDEV_KIND_SIT, NETDEV_KIND_GRE, NETDEV_KIND_GRETAP) &&
+        if (IN_SET(netdev->kind, NETDEV_KIND_VTI, NETDEV_KIND_IPIP, NETDEV_KIND_SIT, NETDEV_KIND_GRE, NETDEV_KIND_GRETAP, NETDEV_KIND_ERSPAN) &&
             (t->family != AF_INET || in_addr_is_null(t->family, &t->local))) {
                 log_netdev_error(netdev,
-                                 "vti/ipip/sit/gre/gretap tunnel without a local IPv4 address configured in %s. Ignoring", filename);
+                                 "vti/ipip/sit/gre/gretap/erspan tunnel without a local IPv4 address configured in %s. Ignoring", filename);
                 return -EINVAL;
         }
 
@@ -453,6 +527,11 @@ static int netdev_tunnel_verify(NetDev *netdev, const char *filename) {
                 return -EINVAL;
         }
 
+        if (netdev->kind == NETDEV_KIND_ERSPAN && (t->erspan_index >= (1 << 20) || t->erspan_index == 0)) {
+                log_netdev_error(netdev, "Invalid erspan index %d. Ignoring", t->erspan_index);
+                return -EINVAL;
+        }
+
         return 0;
 }
 
@@ -729,6 +808,18 @@ static void ip6gre_init(NetDev *n) {
         t->ttl = DEFAULT_TNL_HOP_LIMIT;
 }
 
+static void erspan_init(NetDev *n) {
+        Tunnel *t;
+
+        assert(n);
+
+        t = ERSPAN(n);
+
+        assert(t);
+
+        t->erspan_sequence = -1;
+}
+
 static void ip6tnl_init(NetDev *n) {
         Tunnel *t = IP6TNL(n);
 
@@ -822,3 +913,12 @@ const NetDevVTable ip6tnl_vtable = {
         .create_type = NETDEV_CREATE_STACKED,
         .config_verify = netdev_tunnel_verify,
 };
+
+const NetDevVTable erspan_vtable = {
+        .object_size = sizeof(Tunnel),
+        .init = erspan_init,
+        .sections = "Match\0NetDev\0Tunnel\0",
+        .fill_message_create = netdev_erspan_fill_message_create,
+        .create_type = NETDEV_CREATE_INDEPENDENT,
+        .config_verify = netdev_tunnel_verify,
+};

src/network/netdev/tunnel.h

@@ -29,6 +29,7 @@ typedef struct Tunnel {
         int family;
         int ipv6_flowlabel;
         int allow_localremote;
+        int erspan_sequence;
 
         unsigned ttl;
         unsigned tos;
@@ -37,6 +38,7 @@ typedef struct Tunnel {
         uint32_t key;
         uint32_t ikey;
         uint32_t okey;
+        uint32_t erspan_index;
 
         union in_addr_union local;
         union in_addr_union remote;
@@ -65,6 +67,7 @@ DEFINE_NETDEV_CAST(SIT, Tunnel);
 DEFINE_NETDEV_CAST(VTI, Tunnel);
 DEFINE_NETDEV_CAST(VTI6, Tunnel);
 DEFINE_NETDEV_CAST(IP6TNL, Tunnel);
+DEFINE_NETDEV_CAST(ERSPAN, Tunnel);
 extern const NetDevVTable ipip_vtable;
 extern const NetDevVTable sit_vtable;
 extern const NetDevVTable vti_vtable;
@@ -74,6 +77,7 @@ extern const NetDevVTable gretap_vtable;
 extern const NetDevVTable ip6gre_vtable;
 extern const NetDevVTable ip6gretap_vtable;
 extern const NetDevVTable ip6tnl_vtable;
+extern const NetDevVTable erspan_vtable;
 
 const char *ip6tnl_mode_to_string(Ip6TnlMode d) _const_;
 Ip6TnlMode ip6tnl_mode_from_string(const char *d) _pure_;