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flow_dissector: handle no-skb use case 

When called without skb, gather all required data from the
__skb_flow_dissect's arguments and use recently introduces
no-skb mode of bpf flow dissector.

Note: WARN_ON_ONCE(!net) will now trigger for eth_get_headlen users.

Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Stanislav Fomichev 2019-04-22 08:55:47 -07:00 committed by Daniel Borkmann
parent 3cbf4ffba5
commit 9b52e3f267
2 changed files with 25 additions and 32 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
include/linux/skbuff.h
View File

@ -1279,11 +1279,6 @@ struct bpf_flow_dissector;
bool bpf_flow_dissect(struct bpf_prog *prog, struct bpf_flow_dissector *ctx,
__be16 proto, int nhoff, int hlen);
struct bpf_flow_keys;
bool __skb_flow_bpf_dissect(struct bpf_prog *prog,
const struct sk_buff *skb,
struct flow_dissector *flow_dissector,
struct bpf_flow_keys *flow_keys);
bool __skb_flow_dissect(const struct net *net,
const struct sk_buff *skb,
struct flow_dissector *flow_dissector,

52
net/core/flow_dissector.c
View File

@ -683,22 +683,6 @@ static void __skb_flow_bpf_to_target(const struct bpf_flow_keys *flow_keys,
}
}
bool __skb_flow_bpf_dissect(struct bpf_prog *prog,
const struct sk_buff *skb,
struct flow_dissector *flow_dissector,
struct bpf_flow_keys *flow_keys)
{
struct bpf_flow_dissector ctx = {
.flow_keys = flow_keys,
.skb = skb,
.data = skb->data,
.data_end = skb->data + skb_headlen(skb),
};
return bpf_flow_dissect(prog, &ctx, skb->protocol,
skb_network_offset(skb), skb_headlen(skb));
}
bool bpf_flow_dissect(struct bpf_prog *prog, struct bpf_flow_dissector *ctx,
__be16 proto, int nhoff, int hlen)
{
@ -753,6 +737,7 @@ bool __skb_flow_dissect(const struct net *net,
struct flow_dissector_key_icmp *key_icmp;
struct flow_dissector_key_tags *key_tags;
struct flow_dissector_key_vlan *key_vlan;
struct bpf_prog *attached = NULL;
enum flow_dissect_ret fdret;
enum flow_dissector_key_id dissector_vlan = FLOW_DISSECTOR_KEY_MAX;
int num_hdrs = 0;
@ -795,26 +780,39 @@ bool __skb_flow_dissect(const struct net *net,
target_container);
if (skb) {
struct bpf_flow_keys flow_keys;
struct bpf_prog *attached = NULL;
rcu_read_lock();
if (!net) {
if (skb->dev)
net = dev_net(skb->dev);
else if (skb->sk)
net = sock_net(skb->sk);
else
WARN_ON_ONCE(1);
}
}
if (net)
attached = rcu_dereference(net->flow_dissector_prog);
WARN_ON_ONCE(!net);
if (net) {
rcu_read_lock();
attached = rcu_dereference(net->flow_dissector_prog);
if (attached) {
ret = __skb_flow_bpf_dissect(attached, skb,
flow_dissector,
&flow_keys);
struct bpf_flow_keys flow_keys;
struct bpf_flow_dissector ctx = {
.flow_keys = &flow_keys,
.data = data,
.data_end = data + hlen,
};
__be16 n_proto = proto;
if (skb) {
ctx.skb = skb;
/* we can't use 'proto' in the skb case
* because it might be set to skb->vlan_proto
* which has been pulled from the data
*/
n_proto = skb->protocol;
}
ret = bpf_flow_dissect(attached, &ctx, n_proto, nhoff,
hlen);
__skb_flow_bpf_to_target(&flow_keys, flow_dissector,
target_container);
rcu_read_unlock();