Messages in this thread | | | From | Matteo Croce <> | Date | Fri, 20 Dec 2019 13:36:59 +0100 | Subject | Re: [PATCH net-next v2] openvswitch: add TTL decrement action |
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On Tue, Dec 17, 2019 at 5:30 PM Nikolay Aleksandrov <nikolay@cumulusnetworks.com> wrote: > > On 17/12/2019 17:51, Matteo Croce wrote: > > 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 <bindiyakurle@gmail.com> > > Signed-off-by: Bindiya Kurle <bindiyakurle@gmail.com> > > Signed-off-by: Matteo Croce <mcroce@redhat.com> > > --- > > 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] > > +} > > + > > /* 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
> 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
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