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, send the
packet to userspace via output_userspace() to take care of it.
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,1
in_port(1),eth(),eth_type(0x0800), packets:0, bytes:0, used:never,
actions:dec_ttl,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-authored-by: Bindiya Kurle <[email protected]>
Signed-off-by: Bindiya Kurle <[email protected]>
Signed-off-by: Matteo Croce <[email protected]>
---
include/uapi/linux/openvswitch.h | 2 ++
net/openvswitch/actions.c | 46 ++++++++++++++++++++++++++++++++
net/openvswitch/flow_netlink.c | 6 +++++
3 files changed, 54 insertions(+)
diff --git a/include/uapi/linux/openvswitch.h b/include/uapi/linux/openvswitch.h
index 1887a451c388..a3bdb1ecd1e7 100644
--- a/include/uapi/linux/openvswitch.h
+++ b/include/uapi/linux/openvswitch.h
@@ -890,6 +890,7 @@ struct check_pkt_len_arg {
* @OVS_ACTION_ATTR_CHECK_PKT_LEN: Check the packet length and execute a set
* of actions if greater than the specified packet length, else execute
* another set of actions.
+ * @OVS_ACTION_ATTR_DEC_TTL: Decrement the IP TTL.
*
* Only a single header can be set with a single %OVS_ACTION_ATTR_SET. Not all
* fields within a header are modifiable, e.g. the IPv4 protocol and fragment
@@ -925,6 +926,7 @@ enum ovs_action_attr {
OVS_ACTION_ATTR_METER, /* u32 meter ID. */
OVS_ACTION_ATTR_CLONE, /* Nested OVS_CLONE_ATTR_*. */
OVS_ACTION_ATTR_CHECK_PKT_LEN, /* Nested OVS_CHECK_PKT_LEN_ATTR_*. */
+ OVS_ACTION_ATTR_DEC_TTL, /* Decrement ttl action */
__OVS_ACTION_ATTR_MAX, /* Nothing past this will be accepted
* from userspace. */
diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c
index 12936c151cc0..077b7f309c93 100644
--- a/net/openvswitch/actions.c
+++ b/net/openvswitch/actions.c
@@ -1174,6 +1174,43 @@ 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 = ipv6_hdr(skb);
+
+ err = skb_ensure_writable(skb, skb_network_offset(skb) +
+ sizeof(*nh));
+ if (unlikely(err))
+ return err;
+
+ if (nh->hop_limit <= 1)
+ return -EHOSTUNREACH;
+
+ key->ip.ttl = --nh->hop_limit;
+ } else {
+ struct iphdr *nh = ip_hdr(skb);
+ u8 old_ttl;
+
+ err = skb_ensure_writable(skb, skb_network_offset(skb) +
+ sizeof(*nh));
+ if (unlikely(err))
+ return err;
+
+ 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,
@@ -1345,6 +1382,15 @@ 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) {
+ output_userspace(dp, skb, key, a, attr,
+ len, OVS_CB(skb)->cutlen);
+ OVS_CB(skb)->cutlen = 0;
+ }
+ break;
}
if (unlikely(err)) {
diff --git a/net/openvswitch/flow_netlink.c b/net/openvswitch/flow_netlink.c
index 65c2e3458ff5..d17f2d4b420f 100644
--- a/net/openvswitch/flow_netlink.c
+++ b/net/openvswitch/flow_netlink.c
@@ -79,6 +79,7 @@ static bool actions_may_change_flow(const struct nlattr
*actions)
case OVS_ACTION_ATTR_SET_MASKED:
case OVS_ACTION_ATTR_METER:
case OVS_ACTION_ATTR_CHECK_PKT_LEN:
+ case OVS_ACTION_ATTR_DEC_TTL:
default:
return true;
}
@@ -3005,6 +3006,7 @@ static int __ovs_nla_copy_actions(struct net *net, const
struct nlattr *attr,
[OVS_ACTION_ATTR_METER] = sizeof(u32),
[OVS_ACTION_ATTR_CLONE] = (u32)-1,
[OVS_ACTION_ATTR_CHECK_PKT_LEN] = (u32)-1,
+ [OVS_ACTION_ATTR_DEC_TTL] = 0,
};
const struct ovs_action_push_vlan *vlan;
int type = nla_type(a);
@@ -3233,6 +3235,10 @@ static int __ovs_nla_copy_actions(struct net *net, const
struct nlattr *attr,
break;
}
+ case OVS_ACTION_ATTR_DEC_TTL:
+ /* Nothing to do. */
+ break;
+
default:
OVS_NLERR(log, "Unknown Action type %d", type);
return -EINVAL;
--
2.23.0
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