[ovs-discuss] Problems executing decap(eth)+encap(eth) actions

Jaime Caamaño Ruiz jcaamano at suse.de
Fri Oct 19 08:39:00 UTC 2018


Hello

When using nsh encapsulation, it's useful to normalize your pipeline to
packet_type=nsh, poping an ethernet header on input if necessary and
pushing an ethernet header again if required before output.

But it seems to be problematic:

---
2018-10-18T13:10:59.196Z|00010|dpif(handler3)|WARN|system at ovs-system:
execute pop_eth,push_eth(src=fe:16:3e:c1:9e:87,dst=fa:16:3e:c1:9e:87),5
failed (Invalid argument) on packet
vlan_tci=0x0000,dl_src=fa:16:3e:c2:e6:68,dl_dst=fe:16:3e:c2:e6:68,dl_ty
pe=0x894f,nsh_flags=0,nsh_ttl=63,nsh_mdtype=1,nsh_np=3,nsh_spi=0x1a,nsh
_si=254,nsh_c1=0xc0a82a01,nsh_c2=0x3,nsh_c3=0x0,nsh_c4=0x90000100,nw_pr
oto=0,nw_tos=0,nw_ecn=0,nw_ttl=0
 with metadata
skb_priority(0),tunnel(tun_id=0x0,src=192.168.42.1,dst=192.168.42.3,ttl
=64,tp_src=47656,tp_dst=4789,flags(key)),skb_mark(0),in_port(4) mtu 0
---

Looking at the code datapath/flow_netlink.c @ __ovs_nla_copy_actions:

                case OVS_ACTION_ATTR_PUSH_ETH:
                        /* Disallow pushing an Ethernet header if one
                         * is already present */
                        if (mac_proto != MAC_PROTO_NONE)
                                return -EINVAL;
                        mac_proto = MAC_PROTO_NONE;
                        break;

                case OVS_ACTION_ATTR_POP_ETH:
                        if (mac_proto != MAC_PROTO_ETHERNET)
                                return -EINVAL;
                        if (vlan_tci & htons(VLAN_TAG_PRESENT))
                                return -EINVAL;
                        mac_proto = MAC_PROTO_ETHERNET;
                        break;


Isn't the mac_proto set inverted here, should'nt it look like this?


                case OVS_ACTION_ATTR_PUSH_ETH:
                        /* Disallow pushing an Ethernet header if one
                         * is already present */
                        if (mac_proto != MAC_PROTO_NONE)
                                return -EINVAL;
                        mac_proto = MAC_PROTO_ETHERNET;
                        break;

                case OVS_ACTION_ATTR_POP_ETH:
                        if (mac_proto != MAC_PROTO_ETHERNET)
                                return -EINVAL;
                        if (vlan_tci & htons(VLAN_TAG_PRESENT))
                                return -EINVAL;
                        mac_proto = MAC_PROTO_NONE;
                        break;


BR
Jaime.


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