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netfilter: flowtable: consolidate xmit path

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Use dev_queue_xmit() for the XMIT_NEIGH case. Store the interface index
of the real device behind the vlan/pppoe device, this introduces  an
extra lookup for the real device in the xmit path because rt->dst.dev
provides the vlan/pppoe device.

XMIT_NEIGH now looks more similar to XMIT_DIRECT but the check for stale
dst and the neighbour lookup still remain in place which is convenient
to deal with network topology changes.

Note that nft_flow_route() needs to relax the check for _XMIT_NEIGH so
the existing basic xfrm offload (which only works in one direction) does
not break.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Pablo Neira Ayuso
2025-10-10 12:32:35 +02:00
parent 93d7a7ed07
commit b5964aac51
4 changed files with 57 additions and 39 deletions
Download Patch File Download Diff File Expand all files Collapse all files

1
include/net/netfilter/nf_flow_table.h
View File

@@ -141,6 +141,7 @@ struct flow_offload_tuple {
union {
struct {
struct dst_entry *dst_cache;
u32 ifidx;
u32 dst_cookie;
};
struct {

1
net/netfilter/nf_flow_table_core.c
View File

@@ -132,6 +132,7 @@ static int flow_offload_fill_route(struct flow_offload *flow,
break;
case FLOW_OFFLOAD_XMIT_XFRM:
case FLOW_OFFLOAD_XMIT_NEIGH:
flow_tuple->ifidx = route->tuple[dir].out.ifindex;
flow_tuple->dst_cache = dst;
flow_tuple->dst_cookie = flow_offload_dst_cookie(flow_tuple);
break;

87
net/netfilter/nf_flow_table_ip.c
View File

@@ -333,19 +333,18 @@ static void nf_flow_encap_pop(struct sk_buff *skb,
}
}
struct nf_flow_xmit {
const void *dest;
const void *source;
struct net_device *outdev;
};
static unsigned int nf_flow_queue_xmit(struct net *net, struct sk_buff *skb,
const struct flow_offload_tuple_rhash *tuplehash,
unsigned short type)
struct nf_flow_xmit *xmit)
{
struct net_device *outdev;
outdev = dev_get_by_index_rcu(net, tuplehash->tuple.out.ifidx);
if (!outdev)
return NF_DROP;
skb->dev = outdev;
dev_hard_header(skb, skb->dev, type, tuplehash->tuple.out.h_dest,
tuplehash->tuple.out.h_source, skb->len);
skb->dev = xmit->outdev;
dev_hard_header(skb, skb->dev, ntohs(skb->protocol),
xmit->dest, xmit->source, skb->len);
dev_queue_xmit(skb);
return NF_STOLEN;
@@ -424,10 +423,10 @@ nf_flow_offload_ip_hook(void *priv, struct sk_buff *skb,
struct nf_flowtable_ctx ctx = {
.in = state->in,
};
struct nf_flow_xmit xmit = {};
struct flow_offload *flow;
struct net_device *outdev;
struct neighbour *neigh;
struct rtable *rt;
__be32 nexthop;
int ret;
tuplehash = nf_flow_offload_lookup(&ctx, flow_table, skb);
@@ -454,25 +453,34 @@ nf_flow_offload_ip_hook(void *priv, struct sk_buff *skb,
switch (tuplehash->tuple.xmit_type) {
case FLOW_OFFLOAD_XMIT_NEIGH:
rt = dst_rtable(tuplehash->tuple.dst_cache);
outdev = rt->dst.dev;
skb->dev = outdev;
nexthop = rt_nexthop(rt, flow->tuplehash[!dir].tuple.src_v4.s_addr);
xmit.outdev = dev_get_by_index_rcu(state->net, tuplehash->tuple.ifidx);
if (!xmit.outdev) {
flow_offload_teardown(flow);
return NF_DROP;
}
neigh = ip_neigh_gw4(rt->dst.dev, rt_nexthop(rt, flow->tuplehash[!dir].tuple.src_v4.s_addr));
if (IS_ERR(neigh)) {
flow_offload_teardown(flow);
return NF_DROP;
}
xmit.dest = neigh->ha;
skb_dst_set_noref(skb, &rt->dst);
neigh_xmit(NEIGH_ARP_TABLE, outdev, &nexthop, skb);
ret = NF_STOLEN;
break;
case FLOW_OFFLOAD_XMIT_DIRECT:
ret = nf_flow_queue_xmit(state->net, skb, tuplehash, ETH_P_IP);
if (ret == NF_DROP)
xmit.outdev = dev_get_by_index_rcu(state->net, tuplehash->tuple.out.ifidx);
if (!xmit.outdev) {
flow_offload_teardown(flow);
return NF_DROP;
}
xmit.dest = tuplehash->tuple.out.h_dest;
xmit.source = tuplehash->tuple.out.h_source;
break;
default:
WARN_ON_ONCE(1);
ret = NF_DROP;
break;
return NF_DROP;
}
return ret;
return nf_flow_queue_xmit(state->net, skb, &xmit);
}
EXPORT_SYMBOL_GPL(nf_flow_offload_ip_hook);
@@ -719,9 +727,9 @@ nf_flow_offload_ipv6_hook(void *priv, struct sk_buff *skb,
struct nf_flowtable_ctx ctx = {
.in = state->in,
};
const struct in6_addr *nexthop;
struct nf_flow_xmit xmit = {};
struct flow_offload *flow;
struct net_device *outdev;
struct neighbour *neigh;
struct rt6_info *rt;
int ret;
@@ -749,24 +757,33 @@ nf_flow_offload_ipv6_hook(void *priv, struct sk_buff *skb,
switch (tuplehash->tuple.xmit_type) {
case FLOW_OFFLOAD_XMIT_NEIGH:
rt = dst_rt6_info(tuplehash->tuple.dst_cache);
outdev = rt->dst.dev;
skb->dev = outdev;
nexthop = rt6_nexthop(rt, &flow->tuplehash[!dir].tuple.src_v6);
xmit.outdev = dev_get_by_index_rcu(state->net, tuplehash->tuple.ifidx);
if (!xmit.outdev) {
flow_offload_teardown(flow);
return NF_DROP;
}
neigh = ip_neigh_gw6(rt->dst.dev, rt6_nexthop(rt, &flow->tuplehash[!dir].tuple.src_v6));
if (IS_ERR(neigh)) {
flow_offload_teardown(flow);
return NF_DROP;
}
xmit.dest = neigh->ha;
skb_dst_set_noref(skb, &rt->dst);
neigh_xmit(NEIGH_ND_TABLE, outdev, nexthop, skb);
ret = NF_STOLEN;
break;
case FLOW_OFFLOAD_XMIT_DIRECT:
ret = nf_flow_queue_xmit(state->net, skb, tuplehash, ETH_P_IPV6);
if (ret == NF_DROP)
xmit.outdev = dev_get_by_index_rcu(state->net, tuplehash->tuple.out.ifidx);
if (!xmit.outdev) {
flow_offload_teardown(flow);
return NF_DROP;
}
xmit.dest = tuplehash->tuple.out.h_dest;
xmit.source = tuplehash->tuple.out.h_source;
break;
default:
WARN_ON_ONCE(1);
ret = NF_DROP;
break;
return NF_DROP;
}
return ret;
return nf_flow_queue_xmit(state->net, skb, &xmit);
}
EXPORT_SYMBOL_GPL(nf_flow_offload_ipv6_hook);

7
net/netfilter/nf_flow_table_path.c
View File

@@ -211,11 +211,11 @@ static void nft_dev_forward_path(struct nf_flow_route *route,
}
route->tuple[!dir].in.num_encaps = info.num_encaps;
route->tuple[!dir].in.ingress_vlans = info.ingress_vlans;
route->tuple[dir].out.ifindex = info.outdev->ifindex;
if (info.xmit_type == FLOW_OFFLOAD_XMIT_DIRECT) {
memcpy(route->tuple[dir].out.h_source, info.h_source, ETH_ALEN);
memcpy(route->tuple[dir].out.h_dest, info.h_dest, ETH_ALEN);
route->tuple[dir].out.ifindex = info.outdev->ifindex;
route->tuple[dir].out.hw_ifindex = info.hw_outdev->ifindex;
route->tuple[dir].xmit_type = info.xmit_type;
}
@@ -263,11 +263,10 @@ int nft_flow_route(const struct nft_pktinfo *pkt, const struct nf_conn *ct,
nft_default_forward_path(route, this_dst, dir);
nft_default_forward_path(route, other_dst, !dir);
if (route->tuple[dir].xmit_type == FLOW_OFFLOAD_XMIT_NEIGH &&
route->tuple[!dir].xmit_type == FLOW_OFFLOAD_XMIT_NEIGH) {
if (route->tuple[dir].xmit_type == FLOW_OFFLOAD_XMIT_NEIGH)
nft_dev_forward_path(route, ct, dir, ft);
if (route->tuple[!dir].xmit_type == FLOW_OFFLOAD_XMIT_NEIGH)
nft_dev_forward_path(route, ct, !dir, ft);
}
return 0;
}