Subject: Re: [PATCH net-next v15] openvswitch: enable NSH support

From: "Yang, Yi" <[email-masked]>
Date: Tue, 7 Nov 2017 19:55:04 +0800

On Tue, Nov 07, 2017 at 03:58:35AM -0800, Pravin Shelar wrote:
> On Tue, Nov 7, 2017 at 3:28 AM, Yang, Yi <[email-masked]> wrote:
> > On Tue, Nov 07, 2017 at 06:57:30PM +0800, Pravin Shelar wrote:
> >> On Mon, Nov 6, 2017 at 4:22 AM, Jiri Benc <[email-masked]> wrote:
> >> > On Sat, 4 Nov 2017 07:29:46 -0700, Pravin Shelar wrote:
> >> >> > +int nsh_push(struct sk_buff *skb, const struct nshhdr *pushed_nh)
> >> >> > +{
> >> >> > +       struct nshhdr *nh;
> >> >> > +       size_t length = nsh_hdr_len(pushed_nh);
> >> >> > +       u8 next_proto;
> >> >> > +
> >> >> > +       if (skb->mac_len) {
> >> >> > +               next_proto = TUN_P_ETHERNET;
> >> >> > +       } else {
> >> >> > +               next_proto = tun_p_from_eth_p(skb->protocol);
> >> >> > +               if (!next_proto)
> >> >> > +                       return -EAFNOSUPPORT;
> >> >> check for supported protocols can be moved to flow install validation
> >> >> in __ovs_nla_copy_actions().
> >> >
> >> > You mean the check for !next_proto? It needs to be present for
> >> > correctness of nsh_push. This function has to be self contained, it
> >> > will be used by more callers than opevswitch, namely tc.
> >> >
> >> > It's actually not so much a check for "supported protocols", it's
> >> > rather a check of return value of a function that converts ethertype to
> >> > a 1 byte tunnel type. Blindly using a result of a function that may
> >> > return error would be wrong. Openvswitch is free to perform additional
> >> > checks but this needs to stay.
> >> >
> >> I am not disputing validity of the checks, but it could be done at
> >> flow install phase.
> >> For other use case we could refactor code. If it is too complex, I am
> >> fine with duplicate code that check the protocol in flow install for
> >> now.
> >
> > Ok, I'll add check code in __ovs_nla_copy_actions for both nsh_push and
> > nsh_pop, but how can we get value of skb->protocol in
> > __ovs_nla_copy_actions? Is it argument eth_type of
> > __ovs_nla_copy_actions?
> >
> Yes.

So here is newly-added check code, is it ok?

diff --git a/net/openvswitch/flow_netlink.c b/net/openvswitch/flow_netlink.c
index fa07a17..b64b754 100644
--- a/net/openvswitch/flow_netlink.c
+++ b/net/openvswitch/flow_netlink.c
@@ -3001,20 +3001,34 @@ static int __ovs_nla_copy_actions(struct net *net, const struct nlattr *attr,
 			mac_proto = MAC_PROTO_ETHERNET;
 			break;
 
-		case OVS_ACTION_ATTR_PUSH_NSH:
+		case OVS_ACTION_ATTR_PUSH_NSH: {
+			u8 next_proto;
+
+			if (mac_proto != MAC_PROTO_ETHERNET) {
+				next_proto = tun_p_from_eth_p(eth_type);
+				if (!next_proto)
+					return -EINVAL;
+			}
 			mac_proto = MAC_PROTO_NONE;
 			if (!validate_nsh(nla_data(a), false, true, true))
 				return -EINVAL;
 			break;
+		}
+
+		case OVS_ACTION_ATTR_POP_NSH: {
+			__be16 inner_proto;
 
-		case OVS_ACTION_ATTR_POP_NSH:
 			if (eth_type != htons(ETH_P_NSH))
 				return -EINVAL;
+			inner_proto = tun_p_to_eth_p(key->nsh.base.np);
+			if (!inner_proto)
+				return -EINVAL;
 			if (key->nsh.base.np == TUN_P_ETHERNET)
 				mac_proto = MAC_PROTO_ETHERNET;
 			else
 				mac_proto = MAC_PROTO_NONE;
 			break;
+		}
 
 		default:
 			OVS_NLERR(log, "Unknown Action type %d", type);