userspace: Add SRv6 tunnel support.

SRv6 (Segment Routing IPv6) tunnel vport is responsible
for encapsulation and decapsulation the inner packets with
IPv6 header and an extended header called SRH
(Segment Routing Header). See spec in:

https://datatracker.ietf.org/doc/html/rfc8754

This patch implements SRv6 tunneling in userspace datapath.
It uses `remote_ip` and `local_ip` options as with existing
tunnel protocols. It also adds a dedicated `srv6_segs` option
to define a sequence of routers called segment list.

Signed-off-by: Nobuhiro MIKI <nmiki@yahoo-corp.jp>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>

18 files changed, 450 insertions, 1 deletions

diff --git a/Documentation/faq/configuration.rst b/Documentation/faq/configuration.rst
index dc6c92446..4df390dc2 100644
--- a/Documentation/faq/configuration.rst
+++ b/Documentation/faq/configuration.rst
@@ -238,6 +238,27 @@ Q: Does Open vSwitch support GTP-U?
                 set int gtpu0 type=gtpu options:key=<teid> \
                 options:remote_ip=172.31.1.1
 
+Q: Does Open vSwitch support SRv6?
+
+    A: Yes. Starting with version 3.2, the Open vSwitch userspace
+    datapath supports SRv6 (Segment Routing over IPv6). The following
+    example shows tunneling to fc00:300::1 via fc00:100::1 and fc00:200::1.
+    In the current implementation, if "IPv6 in IPv6" or "IPv4 in IPv6" packets
+    are routed to this interface, and these packets are not SRv6 packets, they
+    may be dropped, so be careful in workloads with a mix of these tunnels.
+    Also note the following restrictions:
+
+    * Segment list length is limited to 6.
+    * SRv6 packets with other than segments_left = 0 are simply dropped.
+
+    ::
+
+        $ ovs-vsctl add-br br0
+        $ ovs-vsctl add-port br0 srv6_0 -- \
+                set int srv6_0 type=srv6  \
+                options:remote_ip=fc00:100::1 \
+                options:srv6_segs="fc00:100::1,fc00:200::1,fc00:300::1"
+
 Q: How do I connect two bridges?
 
     A: First, why do you want to do this?  Two connected bridges are not much
diff --git a/Documentation/faq/releases.rst b/Documentation/faq/releases.rst
index 9e1b42262..9fb679e30 100644
--- a/Documentation/faq/releases.rst
+++ b/Documentation/faq/releases.rst
@@ -151,6 +151,7 @@ Q: Are all features available with all datapaths?
     Tunnel - ERSPAN                 4.18           2.10         2.10     NO
     Tunnel - ERSPAN-IPv6            4.18           2.10         2.10     NO
     Tunnel - GTP-U                  NO             NO           2.14     NO
+    Tunnel - SRv6                   NO             NO           3.2      NO
     Tunnel - Bareudp                5.7            NO           NO       NO
     QoS - Policing                  YES            1.1          2.6      NO
     QoS - Shaping                   YES            1.1          NO       NO
diff --git a/NEWS b/NEWS
index 8771ee618..b6418c36e 100644
--- a/NEWS
+++ b/NEWS
@@ -21,6 +21,8 @@ Post-v3.1.0
      * ovs-vswitchd will keep the CAP_SYS_RAWIO capability when started
        with the --hw-rawio-access command line option.  This allows the
        process extra privileges when mapping physical interconnect memory.
+   - SRv6 Tunnel Protocol
+     * Added support for userspace datapath (only).
 
 
 v3.1.0 - 16 Feb 2023
diff --git a/include/linux/openvswitch.h b/include/linux/openvswitch.h
index bc8f74991..e305c3315 100644
--- a/include/linux/openvswitch.h
+++ b/include/linux/openvswitch.h
@@ -254,6 +254,7 @@ enum ovs_vport_type {
 	OVS_VPORT_TYPE_IP6GRE = 109,
 	OVS_VPORT_TYPE_GTPU = 110,
 	OVS_VPORT_TYPE_BAREUDP = 111,  /* Bareudp tunnel. */
+	OVS_VPORT_TYPE_SRV6 = 112,  /* SRv6 tunnel. */
 	__OVS_VPORT_TYPE_MAX
 };
 
diff --git a/include/sparse/netinet/in.h b/include/sparse/netinet/in.h
index 21deceb28..009272816 100644
--- a/include/sparse/netinet/in.h
+++ b/include/sparse/netinet/in.h
@@ -68,6 +68,7 @@ struct sockaddr_in6 {
 #define IPPROTO_HOPOPTS 0
 #define IPPROTO_ICMP 1
 #define IPPROTO_IGMP 2
+#define IPPROTO_IPIP 4
 #define IPPROTO_TCP 6
 #define IPPROTO_UDP 17
 #define IPPROTO_ROUTING 43
diff --git a/lib/dpif-netlink-rtnl.c b/lib/dpif-netlink-rtnl.c
index 4fc42daed..5788294ae 100644
--- a/lib/dpif-netlink-rtnl.c
+++ b/lib/dpif-netlink-rtnl.c
@@ -129,6 +129,8 @@ vport_type_to_kind(enum ovs_vport_type type,
         }
     case OVS_VPORT_TYPE_GTPU:
         return NULL;
+    case OVS_VPORT_TYPE_SRV6:
+        return "srv6";
     case OVS_VPORT_TYPE_BAREUDP:
         return "bareudp";
     case OVS_VPORT_TYPE_NETDEV:
@@ -319,6 +321,7 @@ dpif_netlink_rtnl_verify(const struct netdev_tunnel_config *tnl_cfg,
     case OVS_VPORT_TYPE_LISP:
     case OVS_VPORT_TYPE_STT:
     case OVS_VPORT_TYPE_GTPU:
+    case OVS_VPORT_TYPE_SRV6:
     case OVS_VPORT_TYPE_UNSPEC:
     case __OVS_VPORT_TYPE_MAX:
     default:
@@ -411,6 +414,7 @@ dpif_netlink_rtnl_create(const struct netdev_tunnel_config *tnl_cfg,
     case OVS_VPORT_TYPE_LISP:
     case OVS_VPORT_TYPE_STT:
     case OVS_VPORT_TYPE_GTPU:
+    case OVS_VPORT_TYPE_SRV6:
     case OVS_VPORT_TYPE_UNSPEC:
     case __OVS_VPORT_TYPE_MAX:
     default:
@@ -519,6 +523,7 @@ dpif_netlink_rtnl_port_destroy(const char *name, const char *type)
     case OVS_VPORT_TYPE_ERSPAN:
     case OVS_VPORT_TYPE_IP6ERSPAN:
     case OVS_VPORT_TYPE_IP6GRE:
+    case OVS_VPORT_TYPE_SRV6:
     case OVS_VPORT_TYPE_BAREUDP:
         return dpif_netlink_rtnl_destroy(name);
     case OVS_VPORT_TYPE_NETDEV:
diff --git a/lib/dpif-netlink.c b/lib/dpif-netlink.c
index ebe7b5cb1..55b5b0a85 100644
--- a/lib/dpif-netlink.c
+++ b/lib/dpif-netlink.c
@@ -919,6 +919,9 @@ get_vport_type(const struct dpif_netlink_vport *vport)
     case OVS_VPORT_TYPE_GTPU:
         return "gtpu";
 
+    case OVS_VPORT_TYPE_SRV6:
+        return "srv6";
+
     case OVS_VPORT_TYPE_BAREUDP:
         return "bareudp";
 
@@ -957,6 +960,8 @@ netdev_to_ovs_vport_type(const char *type)
         return OVS_VPORT_TYPE_GRE;
     } else if (!strcmp(type, "gtpu")) {
         return OVS_VPORT_TYPE_GTPU;
+    } else if (!strcmp(type, "srv6")) {
+        return OVS_VPORT_TYPE_SRV6;
     } else if (!strcmp(type, "bareudp")) {
         return OVS_VPORT_TYPE_BAREUDP;
     } else {
diff --git a/lib/netdev-native-tnl.c b/lib/netdev-native-tnl.c
index b89dfdd52..9abdf5107 100644
--- a/lib/netdev-native-tnl.c
+++ b/lib/netdev-native-tnl.c
@@ -845,6 +845,136 @@ netdev_gtpu_build_header(const struct netdev *netdev,
     return 0;
 }
 
+int
+netdev_srv6_build_header(const struct netdev *netdev,
+                         struct ovs_action_push_tnl *data,
+                         const struct netdev_tnl_build_header_params *params)
+{
+    struct netdev_vport *dev = netdev_vport_cast(netdev);
+    struct netdev_tunnel_config *tnl_cfg;
+    const struct in6_addr *segs;
+    struct srv6_base_hdr *srh;
+    struct in6_addr *s;
+    ovs_be16 dl_type;
+    int err = 0;
+    int nr_segs;
+    int i;
+
+    ovs_mutex_lock(&dev->mutex);
+    tnl_cfg = &dev->tnl_cfg;
+
+    if (tnl_cfg->srv6_num_segs) {
+        nr_segs = tnl_cfg->srv6_num_segs;
+        segs = tnl_cfg->srv6_segs;
+    } else {
+        /*
+         * If explicit segment list setting is omitted, tunnel destination
+         * is considered to be the first segment list.
+         */
+        nr_segs = 1;
+        segs = &params->flow->tunnel.ipv6_dst;
+    }
+
+    if (!ipv6_addr_equals(&segs[0], &params->flow->tunnel.ipv6_dst)) {
+        err = EINVAL;
+        goto out;
+    }
+
+    srh = netdev_tnl_ip_build_header(data, params, IPPROTO_ROUTING);
+    srh->rt_hdr.segments_left = nr_segs - 1;
+    srh->rt_hdr.type = IPV6_SRCRT_TYPE_4;
+    srh->rt_hdr.hdrlen = 2 * nr_segs;
+    srh->last_entry = nr_segs - 1;
+    srh->flags = 0;
+    srh->tag = 0;
+
+    dl_type = params->flow->dl_type;
+    if (dl_type == htons(ETH_TYPE_IP)) {
+        srh->rt_hdr.nexthdr = IPPROTO_IPIP;
+    } else if (dl_type == htons(ETH_TYPE_IPV6)) {
+        srh->rt_hdr.nexthdr = IPPROTO_IPV6;
+    } else {
+        err = EOPNOTSUPP;
+        goto out;
+    }
+
+    s = ALIGNED_CAST(struct in6_addr *,
+                     (char *) srh + sizeof *srh);
+    for (i = 0; i < nr_segs; i++) {
+        /* Segment list is written to the header in reverse order. */
+        memcpy(s, &segs[nr_segs - i - 1], sizeof *s);
+        s++;
+    }
+
+    data->header_len += sizeof *srh + 8 * srh->rt_hdr.hdrlen;
+    data->tnl_type = OVS_VPORT_TYPE_SRV6;
+out:
+    ovs_mutex_unlock(&dev->mutex);
+
+    return err;
+}
+
+void
+netdev_srv6_push_header(const struct netdev *netdev OVS_UNUSED,
+                        struct dp_packet *packet,
+                        const struct ovs_action_push_tnl *data)
+{
+    int ip_tot_size;
+
+    netdev_tnl_push_ip_header(packet, data->header,
+                              data->header_len, &ip_tot_size);
+}
+
+struct dp_packet *
+netdev_srv6_pop_header(struct dp_packet *packet)
+{
+    const struct ovs_16aligned_ip6_hdr *nh = dp_packet_l3(packet);
+    size_t size = dp_packet_l3_size(packet) - IPV6_HEADER_LEN;
+    struct pkt_metadata *md = &packet->md;
+    struct flow_tnl *tnl = &md->tunnel;
+    const struct ip6_rt_hdr *rt_hdr;
+    uint8_t nw_proto = nh->ip6_nxt;
+    const void *data = nh + 1;
+    uint8_t nw_frag = 0;
+    unsigned int hlen;
+
+    /*
+     * Verifies that the routing header is present in the IPv6
+     * extension headers and that its type is SRv6.
+     */
+    if (!parse_ipv6_ext_hdrs(&data, &size, &nw_proto, &nw_frag,
+                             NULL, &rt_hdr)) {
+        goto err;
+    }
+
+    if (!rt_hdr || rt_hdr->type != IPV6_SRCRT_TYPE_4) {
+        goto err;
+    }
+
+    if (rt_hdr->segments_left > 0) {
+        VLOG_WARN_RL(&err_rl, "invalid srv6 segments_left=%d\n",
+                     rt_hdr->segments_left);
+        goto err;
+    }
+
+    if (rt_hdr->nexthdr == IPPROTO_IPIP) {
+        packet->packet_type = htonl(PT_IPV4);
+    } else if (rt_hdr->nexthdr == IPPROTO_IPV6) {
+        packet->packet_type = htonl(PT_IPV6);
+    } else {
+        goto err;
+    }
+
+    pkt_metadata_init_tnl(md);
+    netdev_tnl_ip_extract_tnl_md(packet, tnl, &hlen);
+    dp_packet_reset_packet(packet, hlen);
+
+    return packet;
+err:
+    dp_packet_delete(packet);
+    return NULL;
+}
+
 struct dp_packet *
 netdev_vxlan_pop_header(struct dp_packet *packet)
 {
diff --git a/lib/netdev-native-tnl.h b/lib/netdev-native-tnl.h
index 22ae2ce53..4dad8f978 100644
--- a/lib/netdev-native-tnl.h
+++ b/lib/netdev-native-tnl.h
@@ -65,6 +65,16 @@ netdev_gtpu_build_header(const struct netdev *netdev,
                          struct ovs_action_push_tnl *data,
                          const struct netdev_tnl_build_header_params *p);
 
+struct dp_packet *netdev_srv6_pop_header(struct dp_packet *);
+
+void netdev_srv6_push_header(const struct netdev *,
+                             struct dp_packet *,
+                             const struct ovs_action_push_tnl *);
+
+int netdev_srv6_build_header(const struct netdev *,
+                             struct ovs_action_push_tnl *,
+                             const struct netdev_tnl_build_header_params *);
+
 void
 netdev_tnl_push_udp_header(const struct netdev *netdev,
                            struct dp_packet *packet,
diff --git a/lib/netdev-vport.c b/lib/netdev-vport.c
index 3b3927865..663ee8606 100644
--- a/lib/netdev-vport.c
+++ b/lib/netdev-vport.c
@@ -424,6 +424,35 @@ parse_tunnel_ip(const char *value, bool accept_mcast, bool *flow,
     return 0;
 }
 
+static int
+parse_srv6_segs(char *s, struct in6_addr *segs, uint8_t *num_segs)
+{
+    char *save_ptr = NULL;
+    char *token;
+
+    if (!s) {
+        return EINVAL;
+    }
+
+    *num_segs = 0;
+
+    while ((token = strtok_r(s, ",", &save_ptr)) != NULL) {
+        if (*num_segs == SRV6_MAX_SEGS) {
+            return EINVAL;
+        }
+
+        if (inet_pton(AF_INET6, token, segs) != 1) {
+            return EINVAL;
+        }
+
+        segs++;
+        (*num_segs)++;
+        s = NULL;
+    }
+
+    return 0;
+}
+
 enum tunnel_layers {
     TNL_L2 = 1 << 0,       /* 1 if a tunnel type can carry Ethernet traffic. */
     TNL_L3 = 1 << 1        /* 1 if a tunnel type can carry L3 traffic. */
@@ -443,6 +472,8 @@ tunnel_supported_layers(const char *type,
         return TNL_L3;
     } else if (!strcmp(type, "bareudp")) {
         return TNL_L3;
+    } else if (!strcmp(type, "srv6")) {
+        return TNL_L3;
     } else {
         return TNL_L2;
     }
@@ -750,6 +781,17 @@ set_tunnel_config(struct netdev *dev_, const struct smap *args, char **errp)
                     goto out;
                 }
             }
+        } else if (!strcmp(node->key, "srv6_segs")) {
+            err = parse_srv6_segs(node->value,
+                                  tnl_cfg.srv6_segs,
+                                  &tnl_cfg.srv6_num_segs);
+
+            switch (err) {
+            case EINVAL:
+                ds_put_format(&errors, "%s: bad %s 'srv6_segs'\n",
+                              name, node->value);
+                break;
+            }
         } else if (!strcmp(node->key, "payload_type")) {
             if (!strcmp(node->value, "mpls")) {
                  tnl_cfg.payload_ethertype = htons(ETH_TYPE_MPLS);
@@ -1290,6 +1332,17 @@ netdev_vport_tunnel_register(void)
           },
           {{NULL, NULL, 0, 0}}
         },
+        { "srv6_sys",
+          {
+              TUNNEL_FUNCTIONS_COMMON,
+              .type = "srv6",
+              .build_header = netdev_srv6_build_header,
+              .push_header = netdev_srv6_push_header,
+              .pop_header = netdev_srv6_pop_header,
+              .get_ifindex = NETDEV_VPORT_GET_IFINDEX,
+          },
+          {{NULL, NULL, 0, 0}}
+        },
 
     };
     static struct ovsthread_once once = OVSTHREAD_ONCE_INITIALIZER;
diff --git a/lib/netdev.h b/lib/netdev.h
index acf174927..ff207f56c 100644
--- a/lib/netdev.h
+++ b/lib/netdev.h
@@ -140,6 +140,10 @@ struct netdev_tunnel_config {
     bool erspan_idx_flow;
     bool erspan_dir_flow;
     bool erspan_hwid_flow;
+
+    uint8_t srv6_num_segs;
+    #define SRV6_MAX_SEGS 6
+    struct in6_addr srv6_segs[SRV6_MAX_SEGS];
 };
 
 void netdev_run(void);
diff --git a/lib/packets.h b/lib/packets.h
index 70cd07222..9465bec16 100644
--- a/lib/packets.h
+++ b/lib/packets.h
@@ -706,6 +706,10 @@ char *ip_parse_cidr_len(const char *s, int *n, ovs_be32 *ip,
 #define IPPROTO_IGMP 2
 #endif
 
+#ifndef IPPROTO_IPIP
+#define IPPROTO_IPIP 4
+#endif
+
 #ifndef IPPROTO_UDPLITE
 #define IPPROTO_UDPLITE 136
 #endif
@@ -1523,6 +1527,17 @@ BUILD_ASSERT_DECL(sizeof(struct vxlanhdr) == 8);
 #define VXLAN_F_GPE  0x4000
 #define VXLAN_HF_GPE 0x04000000
 
+/* SRv6 protocol header. */
+#define IPV6_SRCRT_TYPE_4 4
+#define SRV6_BASE_HDR_LEN 8
+struct srv6_base_hdr {
+    struct ip6_rt_hdr rt_hdr;
+    uint8_t last_entry;
+    uint8_t flags;
+    ovs_be16 tag;
+};
+BUILD_ASSERT_DECL(sizeof(struct srv6_base_hdr) == SRV6_BASE_HDR_LEN);
+
 /* Input values for PACKET_TYPE macros have to be in host byte order.
  * The _BE postfix indicates result is in network byte order. Otherwise result
  * is in host byte order. */
diff --git a/lib/tnl-ports.c b/lib/tnl-ports.c
index 829457ee5..f16409a0b 100644
--- a/lib/tnl-ports.c
+++ b/lib/tnl-ports.c
@@ -126,7 +126,7 @@ map_insert(odp_port_t port, struct eth_addr mac, struct in6_addr *addr,
          /* XXX: No fragments support. */
         match.wc.masks.nw_frag = FLOW_NW_FRAG_MASK;
 
-        /* 'tp_port' is zero for GRE tunnels. In this case it
+        /* 'tp_port' is zero for GRE and SRv6 tunnels. In this case it
          * doesn't make sense to match on UDP port numbers. */
         if (tp_port) {
             match.wc.masks.tp_dst = OVS_BE16_MAX;
@@ -174,6 +174,9 @@ tnl_type_to_nw_proto(const char type[], uint8_t nw_protos[2])
     } else if (!strcmp(type, "gre") || !strcmp(type, "erspan") ||
                !strcmp(type, "ip6erspan") || !strcmp(type, "ip6gre")) {
         nw_protos[0] = IPPROTO_GRE;
+    } else if (!strcmp(type, "srv6")) {
+        nw_protos[0] = IPPROTO_IPIP;
+        nw_protos[1] = IPPROTO_IPV6;
     }
 }
 
diff --git a/ofproto/ofproto-dpif-xlate.c b/ofproto/ofproto-dpif-xlate.c
index a9cf3cbee..dee4c7d63 100644
--- a/ofproto/ofproto-dpif-xlate.c
+++ b/ofproto/ofproto-dpif-xlate.c
@@ -3632,6 +3632,10 @@ propagate_tunnel_data_to_flow(struct xlate_ctx *ctx, struct eth_addr dmac,
     case OVS_VPORT_TYPE_BAREUDP:
         nw_proto = IPPROTO_UDP;
         break;
+    case OVS_VPORT_TYPE_SRV6:
+        nw_proto = (flow->dl_type == htons(ETH_TYPE_IP))
+                   ? IPPROTO_IPIP : IPPROTO_IPV6;
+        break;
     case OVS_VPORT_TYPE_LISP:
     case OVS_VPORT_TYPE_STT:
     case OVS_VPORT_TYPE_UNSPEC:
diff --git a/tests/system-kmod-macros.at b/tests/system-kmod-macros.at
index 822a80618..fb15a5a7c 100644
--- a/tests/system-kmod-macros.at
+++ b/tests/system-kmod-macros.at
@@ -202,6 +202,14 @@ m4_define([OVS_CHECK_KERNEL_EXCL],
     AT_SKIP_IF([ ! ( test $version -lt $1 || ( test $version -eq $1 && test $sublevel -lt $2 ) || test $version -gt $3 || ( test $version -eq $3 && test $sublevel -gt $4 ) ) ])
 ])
 
+# OVS_CHECK_SRV6()
+#
+# The kernel datapath does not support this feature.
+m4_define([OVS_CHECK_SRV6],
+[
+    AT_SKIP_IF([:])
+])
+
 # CHECK_LATER_IPV6_FRAGMENTS()
 #
 # Upstream kernels beetween 4.20 and 5.19 are not parsing IPv6 fragments
diff --git a/tests/system-traffic.at b/tests/system-traffic.at
index 39a481752..4c378e1d0 100644
--- a/tests/system-traffic.at
+++ b/tests/system-traffic.at
@@ -1164,6 +1164,130 @@ OVS_WAIT_UNTIL([cat p0.pcap | grep -E "IP6 fc00:100::100 > fc00:100::1: GREv0, .
 OVS_TRAFFIC_VSWITCHD_STOP
 AT_CLEANUP
 
+AT_SETUP([datapath - ping over srv6 tunnel])
+OVS_CHECK_TUNNEL_TSO()
+OVS_CHECK_SRV6()
+
+OVS_TRAFFIC_VSWITCHD_START()
+
+ADD_NAMESPACES(at_ns0)
+ADD_NAMESPACES(at_ns1)
+NS_EXEC([at_ns0], [sysctl -w net.ipv6.conf.default.seg6_enabled=1])
+NS_EXEC([at_ns0], [sysctl -w net.ipv4.conf.default.forwarding=1])
+NS_EXEC([at_ns0], [sysctl -w net.ipv6.conf.default.forwarding=1])
+NS_EXEC([at_ns0], [sysctl -w net.ipv6.conf.all.seg6_enabled=1])
+NS_EXEC([at_ns0], [sysctl -w net.ipv4.conf.all.forwarding=1])
+NS_EXEC([at_ns0], [sysctl -w net.ipv6.conf.all.forwarding=1])
+
+dnl Set up underlay link from host into the namespace 'at_ns0'
+dnl using veth pair. Kernel side tunnel endpoint (SID) is
+dnl 'fc00:a::1/128', so add it to the route.
+dnl Only IPPROTO_IPIP(4) and IPPROTO_ICMPV6(58) are needed in underlay link.
+ADD_BR([br-underlay])
+ADD_VETH(p0, at_ns0, br-underlay, "fc00::1/64", [], [], "nodad")
+AT_CHECK([ovs-ofctl add-flow br-underlay "priority=1,actions=drop"])
+AT_CHECK([ovs-ofctl add-flow br-underlay "priority=100,ipv6,nw_proto=4,actions=normal"])
+AT_CHECK([ovs-ofctl add-flow br-underlay "priority=100,ipv6,nw_proto=58,actions=normal"])
+AT_CHECK([ip addr add dev br-underlay "fc00::100/64" nodad])
+AT_CHECK([ip link set dev br-underlay up])
+AT_CHECK([ip route add fc00:a::1/128 dev br-underlay via fc00::1])
+
+dnl Set up tunnel endpoints on OVS outside the namespace.
+ADD_OVS_TUNNEL6([srv6], [br0], [at_srv6], [fc00:a::1], [10.100.100.100/24])
+AT_CHECK([ovs-vsctl set bridge br0 other_config:hwaddr=aa:55:aa:55:00:00])
+AT_CHECK([ip route add 10.1.1.0/24 dev br0 via 10.100.100.1])
+AT_CHECK([arp -s 10.100.100.1 aa:55:aa:55:00:01])
+AT_CHECK([ovs-ofctl add-flow br0 in_port=LOCAL,actions=output:at_srv6])
+AT_CHECK([ovs-ofctl add-flow br0 in_port=at_srv6,actions=mod_dl_dst:aa:55:aa:55:00:00,output:LOCAL])
+
+dnl Set up tunnel endpoints on the namespace 'at_ns0',
+dnl and overlay port on the namespace 'at_ns1'
+ADD_VETH_NS([at_ns0], [veth0], [10.1.1.2/24], [at_ns1], [veth1], [10.1.1.1/24])
+NS_CHECK_EXEC([at_ns0], [ip sr tunsrc set fc00:a::1])
+NS_CHECK_EXEC([at_ns0], [ip route add 10.100.100.0/24 encap seg6 mode encap segs fc00::100 dev p0])
+NS_CHECK_EXEC([at_ns0], [ip -6 route add fc00:a::1 encap seg6local action End.DX4 nh4 0.0.0.0 dev veth0])
+NS_CHECK_EXEC([at_ns1], [ip route add 10.100.100.0/24 via 10.1.1.2 dev veth1])
+
+dnl Linux seems to take a little time to get its IPv6 stack in order. Without
+dnl waiting, we get occasional failures due to the following error:
+dnl "connect: Cannot assign requested address"
+OVS_WAIT_UNTIL([ip netns exec at_ns0 ping6 -c 1 fc00::100])
+
+dnl First, check the underlay.
+NS_CHECK_EXEC([at_ns0], [ping6 -q -c 3 -i 0.3 -w 2 fc00::100 | FORMAT_PING], [0], [dnl
+3 packets transmitted, 3 received, 0% packet loss, time 0ms
+])
+
+dnl Okay, now check the overlay.
+NS_CHECK_EXEC([at_ns1], [ping -q -c 3 -i 0.3 -w 2 10.100.100.100 | FORMAT_PING], [0], [dnl
+3 packets transmitted, 3 received, 0% packet loss, time 0ms
+])
+
+OVS_TRAFFIC_VSWITCHD_STOP
+AT_CLEANUP
+
+AT_SETUP([datapath - ping6 over srv6 tunnel])
+OVS_CHECK_TUNNEL_TSO()
+OVS_CHECK_SRV6()
+
+OVS_TRAFFIC_VSWITCHD_START()
+
+ADD_NAMESPACES(at_ns0)
+ADD_NAMESPACES(at_ns1)
+NS_EXEC([at_ns0], [sysctl -w net.ipv6.conf.default.seg6_enabled=1])
+NS_EXEC([at_ns0], [sysctl -w net.ipv6.conf.default.forwarding=1])
+NS_EXEC([at_ns0], [sysctl -w net.ipv6.conf.all.seg6_enabled=1])
+NS_EXEC([at_ns0], [sysctl -w net.ipv6.conf.all.forwarding=1])
+
+dnl Set up underlay link from host into the namespace 'at_ns0'
+dnl using veth pair. Kernel side tunnel endpoint (SID) is
+dnl 'fc00:a::1/128', so add it to the route.
+dnl Only IPPROTO_IPV6(41) and IPPROTO_ICMPV6(58) are needed in underlay link.
+ADD_BR([br-underlay])
+ADD_VETH(p0, at_ns0, br-underlay, "fc00::1/64", [], [], "nodad")
+AT_CHECK([ovs-ofctl add-flow br-underlay "priority=1,actions=drop"])
+AT_CHECK([ovs-ofctl add-flow br-underlay "priority=100,ipv6,nw_proto=41,actions=normal"])
+AT_CHECK([ovs-ofctl add-flow br-underlay "priority=100,ipv6,nw_proto=58,actions=normal"])
+AT_CHECK([ip addr add dev br-underlay "fc00::100/64" nodad])
+AT_CHECK([ip link set dev br-underlay up])
+AT_CHECK([ip -6 route add fc00:a::1/128 dev br-underlay via fc00::1])
+
+dnl Set up tunnel endpoints on OVS outside the namespace.
+ADD_OVS_TUNNEL6([srv6], [br0], [at_srv6], [fc00:a::1], [fc00:100::100/64])
+AT_CHECK([ovs-vsctl set bridge br0 other_config:hwaddr=aa:55:aa:55:00:00])
+AT_CHECK([ip addr add dev br0 fc00:100::100/64])
+AT_CHECK([ip -6 route add fc00:1::1/128 dev br0 via fc00:100::1])
+AT_CHECK([ip -6 neigh add fc00:100::1 lladdr aa:55:aa:55:00:01 dev br0])
+AT_CHECK([ovs-ofctl add-flow br0 in_port=LOCAL,actions=output:at_srv6])
+AT_CHECK([ovs-ofctl add-flow br0 in_port=at_srv6,actions=mod_dl_dst:aa:55:aa:55:00:00,output:LOCAL])
+
+dnl Set up tunnel endpoints on the namespace 'at_ns0',
+dnl and overlay port on the namespace 'at_ns1'
+ADD_VETH_NS([at_ns0], [veth0], [fc00:1::2/64], [at_ns1], [veth1], [fc00:1::1/64])
+NS_CHECK_EXEC([at_ns0], [ip sr tunsrc set fc00:a::1])
+NS_CHECK_EXEC([at_ns0], [ip -6 route add fc00:100::0/64 encap seg6 mode encap segs fc00::100 dev p0])
+NS_CHECK_EXEC([at_ns0], [ip -6 route add fc00:a::1 encap seg6local action End.DX6 nh6 :: dev veth0])
+NS_CHECK_EXEC([at_ns1], [ip -6 route add fc00:100::/64 via fc00:1::2 dev veth1])
+
+dnl Linux seems to take a little time to get its IPv6 stack in order. Without
+dnl waiting, we get occasional failures due to the following error:
+dnl "connect: Cannot assign requested address"
+OVS_WAIT_UNTIL([ip netns exec at_ns0 ping6 -c 1 fc00::100])
+OVS_WAIT_UNTIL([ip netns exec at_ns1 ping6 -c 1 fc00:100::100])
+
+dnl First, check the underlay.
+NS_CHECK_EXEC([at_ns0], [ping6 -q -c 3 -i 0.3 -w 2 fc00::100 | FORMAT_PING], [0], [dnl
+3 packets transmitted, 3 received, 0% packet loss, time 0ms
+])
+
+dnl Okay, now check the overlay.
+NS_CHECK_EXEC([at_ns1], [ping6 -q -c 3 -i 0.3 -w 2 fc00:100::100 | FORMAT_PING], [0], [dnl
+3 packets transmitted, 3 received, 0% packet loss, time 0ms
+])
+
+OVS_TRAFFIC_VSWITCHD_STOP
+AT_CLEANUP
+
 AT_SETUP([datapath - clone action])
 OVS_TRAFFIC_VSWITCHD_START()
 
diff --git a/tests/system-userspace-macros.at b/tests/system-userspace-macros.at
index 610fa2e94..482079386 100644
--- a/tests/system-userspace-macros.at
+++ b/tests/system-userspace-macros.at
@@ -301,6 +301,12 @@ m4_define([OVS_CHECK_KERNEL_EXCL],
     AT_SKIP_IF([:])
 ])
 
+# OVS_CHECK_SRV6()
+m4_define([OVS_CHECK_SRV6],
+    [AT_SKIP_IF([! ip -6 route add fc00::1/96 encap seg6 mode encap dev lo 2>&1 >/dev/null])
+     AT_CHECK([ip -6 route del fc00::1/96 2>&1 >/dev/null])
+     OVS_CHECK_FIREWALL()])
+
 # CHECK_LATER_IPV6_FRAGMENTS()
 #
 # Userspace is parsing later IPv6 fragments correctly.
diff --git a/tests/tunnel.at b/tests/tunnel.at
index 78cc3f3e9..ddeb66bc9 100644
--- a/tests/tunnel.at
+++ b/tests/tunnel.at
@@ -1223,3 +1223,59 @@ AT_CHECK([ovs-vsctl add-port br0 p1 -- set int p1 type=dummy])
 OVS_APP_EXIT_AND_WAIT([ovs-vswitchd])
 OVS_APP_EXIT_AND_WAIT([ovsdb-server])]
 AT_CLEANUP
+
+AT_SETUP([tunnel - SRV6 basic])
+OVS_VSWITCHD_START([add-port br0 p1 -- set Interface p1 type=dummy \
+                    ofport_request=1 \
+                    -- add-port br0 p2 -- set Interface p2 type=srv6 \
+                    options:remote_ip=flow \
+                    ofport_request=2])
+OVS_VSWITCHD_DISABLE_TUNNEL_PUSH_POP
+
+dnl First setup dummy interface IP address, then add the route
+dnl so that tnl-port table can get valid IP address for the device.
+AT_CHECK([ovs-appctl netdev-dummy/ip6addr br0 fc00::1/64], [0], [OK
+])
+AT_CHECK([ovs-appctl ovs/route/add fc00::0/64 br0], [0], [OK
+])
+AT_CHECK([ovs-appctl ovs/route/show], [0], [dnl
+Route Table:
+User: fc00::/64 dev br0 SRC fc00::1
+])
+
+AT_DATA([flows.txt], [dnl
+in_port=1,actions=set_field:fc00::2->tun_ipv6_dst,output:2
+in_port=2,actions=1
+])
+AT_CHECK([ovs-ofctl add-flows br0 flows.txt])
+
+AT_CHECK([ovs-appctl dpif/show | tail -n +3], [0], [dnl
+    br0 65534/100: (dummy-internal)
+    p1 1/1: (dummy)
+    p2 2/6: (srv6: remote_ip=flow)
+])
+
+AT_CHECK([ovs-appctl tnl/ports/show |sort], [0], [dnl
+Listening ports:
+srv6_sys (6) ref_cnt=1
+srv6_sys (6) ref_cnt=1
+])
+
+AT_CHECK([ovs-appctl ofproto/list-tunnels], [0], [dnl
+port 6: p2 (srv6: ::->flow, key=0, legacy_l3, dp port=6, ttl=64)
+])
+
+dnl Encap: ipv4 inner packet
+AT_CHECK([ovs-appctl ofproto/trace ovs-dummy 'in_port(1),eth(src=50:54:00:00:00:05,dst=50:54:00:00:00:07),eth_type(0x0800),ipv4(src=192.168.0.1,dst=192.168.0.2,proto=6,tos=4,ttl=128,frag=no),tcp(src=8,dst=9)'], [0], [stdout])
+AT_CHECK([tail -1 stdout], [0],
+  [Datapath actions: set(tunnel(ipv6_dst=fc00::2,ttl=64,flags(df))),pop_eth,6
+])
+
+dnl Encap: ipv6 inner packet
+AT_CHECK([ovs-appctl ofproto/trace ovs-dummy 'in_port(1),eth(src=50:54:00:00:00:05,dst=50:54:00:00:00:07),eth_type(0x86dd),ipv6(src=2001:cafe::92,dst=2001:cafe::88,label=0,proto=47,tclass=0x0,hlimit=64)'], [0], [stdout])
+AT_CHECK([tail -1 stdout], [0],
+  [Datapath actions: set(tunnel(ipv6_dst=fc00::2,ttl=64,flags(df))),pop_eth,6
+])
+
+OVS_VSWITCHD_STOP
+AT_CLEANUP