Re: [ovs-dev] [PATCH net-next v2] openvswitch: add TTL decrement action

On Wed, Dec 25, 2019 at 7:16 AM bindiya Kurle [off-list ref] wrote:

Hi Tonghao,
Once this kernel patch is integrated . I will be submitting patch to ovs-dpdk  for implementing dec_ttl action on dpdk datapath.

Good， thanks

Regards,
Bindiya

On Tue, Dec 24, 2019 at 2:12 PM Tonghao Zhang [off-list ref] wrote:

quoted

Hi Matteo,
Did you have plan to implement the TTL decrement action in userspace
datapath(with dpdk),
I am doing some research offloading about TTL decrement action, and
may sent patch TTL decrement offload action,
using dpdk rte_flow.

On Fri, Dec 20, 2019 at 8:37 PM Matteo Croce [off-list ref] wrote:

quoted

On Tue, Dec 17, 2019 at 5:30 PM Nikolay Aleksandrov
[off-list ref] wrote:

quoted

On 17/12/2019 17:51, Matteo Croce wrote:

quoted

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)},1,1
    in_port(1),eth(),eth_type(0x0800), packets:0, bytes:0, used:never, actions:dec_ttl{ttl<=1 action:(drop)},1,2
    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 [off-list ref]
Signed-off-by: Bindiya Kurle <redacted>
Signed-off-by: Matteo Croce <redacted>
---
 include/uapi/linux/openvswitch.h |  22 +++++++
 net/openvswitch/actions.c        |  71 +++++++++++++++++++++
 net/openvswitch/flow_netlink.c   | 105 +++++++++++++++++++++++++++++++
 3 files changed, 198 insertions(+)

Hi Matteo,

[snip]

quoted

+}
+
 /* When 'last' is true, sample() should always consume the 'skb'.
  * Otherwise, sample() should keep 'skb' intact regardless what
  * actions are executed within sample().

@@ -1176,6 +1201,44 @@ 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));

skb_ensure_writable() calls pskb_may_pull() which may reallocate so nh might become invalid.
It seems the IPv4 version below is ok as the ptr is reloaded.

Right

quoted

One q as I don't know ovs that much - can this action be called only with
skb->protocol ==  ETH_P_IP/IPV6 ? I.e. Are we sure that if it's not v6, then it must be v4 ?

I'm adding a check in validate_and_copy_dec_ttl() so only ipv4/ipv6
packet will pass.

Thanks,

--
Matteo Croce
per aspera ad upstream

_______________________________________________
dev mailing list
dev@openvswitch.org
https://mail.openvswitch.org/mailman/listinfo/ovs-dev