openvswitch: add TTL decrement action

New action to decrement TTL instead of setting it to a fixed value.
This action will decrement the TTL and, in case of expired TTL, drop it
or execute an action passed via a nested attribute.
The default TTL expired action is to drop the packet.

Supports both IPv4 and IPv6 via the ttl and hop_limit fields, respectively.

Tested with a corresponding change in the userspace:

    # ovs-dpctl dump-flows
    in_port(2),eth(),eth_type(0x0800), packets:0, bytes:0, used:never, actions:dec_ttl{ttl<=1 action:(drop)},1
    in_port(1),eth(),eth_type(0x0800), packets:0, bytes:0, used:never, actions:dec_ttl{ttl<=1 action:(drop)},2
    in_port(1),eth(),eth_type(0x0806), packets:0, bytes:0, used:never, actions:2
    in_port(2),eth(),eth_type(0x0806), packets:0, bytes:0, used:never, actions:1

    # ping -c1 192.168.0.2 -t 42
    IP (tos 0x0, ttl 41, id 61647, offset 0, flags [DF], proto ICMP (1), length 84)
        192.168.0.1 > 192.168.0.2: ICMP echo request, id 386, seq 1, length 64
    # ping -c1 192.168.0.2 -t 120
    IP (tos 0x0, ttl 119, id 62070, offset 0, flags [DF], proto ICMP (1), length 84)
        192.168.0.1 > 192.168.0.2: ICMP echo request, id 388, seq 1, length 64
    # ping -c1 192.168.0.2 -t 1
    #

Co-developed-by: Bindiya Kurle <bindiyakurle@gmail.com>
Signed-off-by: Bindiya Kurle <bindiyakurle@gmail.com>
Signed-off-by: Matteo Croce <mcroce@redhat.com>
Acked-by: Pravin B Shelar <pshelar@ovn.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/uapi/linux/openvswitch.h b/include/uapi/linux/openvswitch.h
index ae2bff1..9b14519 100644 (file)
--- a/include/uapi/linux/openvswitch.h
+++ b/include/uapi/linux/openvswitch.h
@@ -958,6 +958,7 @@ enum ovs_action_attr {
        OVS_ACTION_ATTR_CLONE,        /* Nested OVS_CLONE_ATTR_*.  */
        OVS_ACTION_ATTR_CHECK_PKT_LEN, /* Nested OVS_CHECK_PKT_LEN_ATTR_*. */
        OVS_ACTION_ATTR_ADD_MPLS,     /* struct ovs_action_add_mpls. */
+       OVS_ACTION_ATTR_DEC_TTL,      /* Nested OVS_DEC_TTL_ATTR_*. */
 
        __OVS_ACTION_ATTR_MAX,        /* Nothing past this will be accepted
                                       * from userspace. */
@@ -1050,4 +1051,10 @@ struct ovs_zone_limit {
        __u32 count;
 };
 
+enum ovs_dec_ttl_attr {
+       OVS_DEC_TTL_ATTR_UNSPEC,
+       OVS_DEC_TTL_ATTR_ACTION,        /* Nested struct nlattr */
+       __OVS_DEC_TTL_ATTR_MAX
+};
+
 #endif /* _LINUX_OPENVSWITCH_H */

diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c
index 7fbfe2a..fc0efd8 100644 (file)
--- a/net/openvswitch/actions.c
+++ b/net/openvswitch/actions.c
@@ -964,6 +964,25 @@ static int output_userspace(struct datapath *dp, struct sk_buff *skb,
        return ovs_dp_upcall(dp, skb, key, &upcall, cutlen);
 }
 
+static int dec_ttl_exception_handler(struct datapath *dp, struct sk_buff *skb,
+                                    struct sw_flow_key *key,
+                                    const struct nlattr *attr, bool last)
+{
+       /* The first action is always 'OVS_DEC_TTL_ATTR_ARG'. */
+       struct nlattr *dec_ttl_arg = nla_data(attr);
+       int rem = nla_len(attr);
+
+       if (nla_len(dec_ttl_arg)) {
+               struct nlattr *actions = nla_next(dec_ttl_arg, &rem);
+
+               if (actions)
+                       return clone_execute(dp, skb, key, 0, actions, rem,
+                                            last, false);
+       }
+       consume_skb(skb);
+       return 0;
+}
+
 /* When 'last' is true, sample() should always consume the 'skb'.
  * Otherwise, sample() should keep 'skb' intact regardless what
  * actions are executed within sample().
@@ -1180,6 +1199,45 @@ static int execute_check_pkt_len(struct datapath *dp, struct sk_buff *skb,
                             nla_len(actions), last, clone_flow_key);
 }
 
+static int execute_dec_ttl(struct sk_buff *skb, struct sw_flow_key *key)
+{
+       int err;
+
+       if (skb->protocol == htons(ETH_P_IPV6)) {
+               struct ipv6hdr *nh;
+
+               err = skb_ensure_writable(skb, skb_network_offset(skb) +
+                                         sizeof(*nh));
+               if (unlikely(err))
+                       return err;
+
+               nh = ipv6_hdr(skb);
+
+               if (nh->hop_limit <= 1)
+                       return -EHOSTUNREACH;
+
+               key->ip.ttl = --nh->hop_limit;
+       } else {
+               struct iphdr *nh;
+               u8 old_ttl;
+
+               err = skb_ensure_writable(skb, skb_network_offset(skb) +
+                                         sizeof(*nh));
+               if (unlikely(err))
+                       return err;
+
+               nh = ip_hdr(skb);
+               if (nh->ttl <= 1)
+                       return -EHOSTUNREACH;
+
+               old_ttl = nh->ttl--;
+               csum_replace2(&nh->check, htons(old_ttl << 8),
+                             htons(nh->ttl << 8));
+               key->ip.ttl = nh->ttl;
+       }
+       return 0;
+}
+
 /* Execute a list of actions against 'skb'. */
 static int do_execute_actions(struct datapath *dp, struct sk_buff *skb,
                              struct sw_flow_key *key,
@@ -1365,6 +1423,15 @@ static int do_execute_actions(struct datapath *dp, struct sk_buff *skb,
 
                        break;
                }
+
+               case OVS_ACTION_ATTR_DEC_TTL:
+                       err = execute_dec_ttl(skb, key);
+                       if (err == -EHOSTUNREACH) {
+                               err = dec_ttl_exception_handler(dp, skb, key,
+                                                               a, true);
+                               return err;
+                       }
+                       break;
                }
 
                if (unlikely(err)) {

diff --git a/net/openvswitch/flow_netlink.c b/net/openvswitch/flow_netlink.c
index 7da4230..1ccd5e0 100644 (file)
--- a/net/openvswitch/flow_netlink.c
+++ b/net/openvswitch/flow_netlink.c
@@ -80,6 +80,7 @@ static bool actions_may_change_flow(const struct nlattr *actions)
                case OVS_ACTION_ATTR_METER:
                case OVS_ACTION_ATTR_CHECK_PKT_LEN:
                case OVS_ACTION_ATTR_ADD_MPLS:
+               case OVS_ACTION_ATTR_DEC_TTL:
                default:
                        return true;
                }
@@ -2495,6 +2496,39 @@ static int validate_and_copy_sample(struct net *net, const struct nlattr *attr,
        return 0;
 }
 
+static int validate_and_copy_dec_ttl(struct net *net,
+                                    const struct nlattr *attr,
+                                    const struct sw_flow_key *key,
+                                    struct sw_flow_actions **sfa,
+                                    __be16 eth_type, __be16 vlan_tci,
+                                    u32 mpls_label_count, bool log)
+{
+       int start, err;
+       u32 nested = true;
+
+       if (!nla_len(attr))
+               return ovs_nla_add_action(sfa, OVS_ACTION_ATTR_DEC_TTL,
+                                         NULL, 0, log);
+
+       start = add_nested_action_start(sfa, OVS_ACTION_ATTR_DEC_TTL, log);
+       if (start < 0)
+               return start;
+
+       err = ovs_nla_add_action(sfa, OVS_DEC_TTL_ATTR_ACTION, &nested,
+                                sizeof(nested), log);
+
+       if (err)
+               return err;
+
+       err = __ovs_nla_copy_actions(net, attr, key, sfa, eth_type,
+                                    vlan_tci, mpls_label_count, log);
+       if (err)
+               return err;
+
+       add_nested_action_end(*sfa, start);
+       return 0;
+}
+
 static int validate_and_copy_clone(struct net *net,
                                   const struct nlattr *attr,
                                   const struct sw_flow_key *key,
@@ -3007,6 +3041,7 @@ static int __ovs_nla_copy_actions(struct net *net, const struct nlattr *attr,
                        [OVS_ACTION_ATTR_CLONE] = (u32)-1,
                        [OVS_ACTION_ATTR_CHECK_PKT_LEN] = (u32)-1,
                        [OVS_ACTION_ATTR_ADD_MPLS] = sizeof(struct ovs_action_add_mpls),
+                       [OVS_ACTION_ATTR_DEC_TTL] = (u32)-1,
                };
                const struct ovs_action_push_vlan *vlan;
                int type = nla_type(a);
@@ -3267,6 +3302,15 @@ static int __ovs_nla_copy_actions(struct net *net, const struct nlattr *attr,
                        break;
                }
 
+               case OVS_ACTION_ATTR_DEC_TTL:
+                       err = validate_and_copy_dec_ttl(net, a, key, sfa,
+                                                       eth_type, vlan_tci,
+                                                       mpls_label_count, log);
+                       if (err)
+                               return err;
+                       skip_copy = true;
+                       break;
+
                default:
                        OVS_NLERR(log, "Unknown Action type %d", type);
                        return -EINVAL;
@@ -3438,6 +3482,26 @@ out:
        return err;
 }
 
+static int dec_ttl_action_to_attr(const struct nlattr *attr,
+                                 struct sk_buff *skb)
+{
+       int err = 0, rem = nla_len(attr);
+       struct nlattr *start;
+
+       start = nla_nest_start_noflag(skb, OVS_ACTION_ATTR_DEC_TTL);
+
+       if (!start)
+               return -EMSGSIZE;
+
+       err = ovs_nla_put_actions(nla_data(attr), rem, skb);
+       if (err)
+               nla_nest_cancel(skb, start);
+       else
+               nla_nest_end(skb, start);
+
+       return err;
+}
+
 static int set_action_to_attr(const struct nlattr *a, struct sk_buff *skb)
 {
        const struct nlattr *ovs_key = nla_data(a);
@@ -3538,6 +3602,12 @@ int ovs_nla_put_actions(const struct nlattr *attr, int len, struct sk_buff *skb)
                                return err;
                        break;
 
+               case OVS_ACTION_ATTR_DEC_TTL:
+                       err = dec_ttl_action_to_attr(a, skb);
+                       if (err)
+                               return err;
+                       break;
+
                default:
                        if (nla_put(skb, type, nla_len(a), nla_data(a)))
                                return -EMSGSIZE;