Commit 2c3af7d9 authored by Stanislav Fomichev's avatar Stanislav Fomichev Committed by Daniel Borkmann

selftests/bpf: fix vlan handling in flow dissector program

When we tail call PROG(VLAN) from parse_eth_proto we don't need to peek
back to handle vlan proto because we didn't adjust nhoff/thoff yet. Use
flow_keys->n_proto, that we set in parse_eth_proto instead and
properly increment nhoff as well.

Also, always use skb->protocol and don't look at skb->vlan_present.
skb->vlan_present indicates that vlan information is stored out-of-band
in skb->vlan_{tci,proto} and vlan header is already pulled from skb.
That means, skb->vlan_present == true is not relevant for BPF flow
dissector.

Add simple test cases with VLAN tagged frames:
  * single vlan for ipv4
  * double vlan for ipv6
Signed-off-by: default avatarStanislav Fomichev <sdf@google.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent b2e54b09
......@@ -39,6 +39,58 @@ static struct bpf_flow_keys pkt_v6_flow_keys = {
.n_proto = __bpf_constant_htons(ETH_P_IPV6),
};
#define VLAN_HLEN 4
static struct {
struct ethhdr eth;
__u16 vlan_tci;
__u16 vlan_proto;
struct iphdr iph;
struct tcphdr tcp;
} __packed pkt_vlan_v4 = {
.eth.h_proto = __bpf_constant_htons(ETH_P_8021Q),
.vlan_proto = __bpf_constant_htons(ETH_P_IP),
.iph.ihl = 5,
.iph.protocol = IPPROTO_TCP,
.iph.tot_len = __bpf_constant_htons(MAGIC_BYTES),
.tcp.urg_ptr = 123,
.tcp.doff = 5,
};
static struct bpf_flow_keys pkt_vlan_v4_flow_keys = {
.nhoff = VLAN_HLEN,
.thoff = VLAN_HLEN + sizeof(struct iphdr),
.addr_proto = ETH_P_IP,
.ip_proto = IPPROTO_TCP,
.n_proto = __bpf_constant_htons(ETH_P_IP),
};
static struct {
struct ethhdr eth;
__u16 vlan_tci;
__u16 vlan_proto;
__u16 vlan_tci2;
__u16 vlan_proto2;
struct ipv6hdr iph;
struct tcphdr tcp;
} __packed pkt_vlan_v6 = {
.eth.h_proto = __bpf_constant_htons(ETH_P_8021AD),
.vlan_proto = __bpf_constant_htons(ETH_P_8021Q),
.vlan_proto2 = __bpf_constant_htons(ETH_P_IPV6),
.iph.nexthdr = IPPROTO_TCP,
.iph.payload_len = __bpf_constant_htons(MAGIC_BYTES),
.tcp.urg_ptr = 123,
.tcp.doff = 5,
};
static struct bpf_flow_keys pkt_vlan_v6_flow_keys = {
.nhoff = VLAN_HLEN * 2,
.thoff = VLAN_HLEN * 2 + sizeof(struct ipv6hdr),
.addr_proto = ETH_P_IPV6,
.ip_proto = IPPROTO_TCP,
.n_proto = __bpf_constant_htons(ETH_P_IPV6),
};
void test_flow_dissector(void)
{
struct bpf_flow_keys flow_keys;
......@@ -68,5 +120,21 @@ void test_flow_dissector(void)
err, errno, retval, duration, size, sizeof(flow_keys));
CHECK_FLOW_KEYS("ipv6_flow_keys", flow_keys, pkt_v6_flow_keys);
err = bpf_prog_test_run(prog_fd, 10, &pkt_vlan_v4, sizeof(pkt_vlan_v4),
&flow_keys, &size, &retval, &duration);
CHECK(size != sizeof(flow_keys) || err || retval != 1, "vlan_ipv4",
"err %d errno %d retval %d duration %d size %u/%lu\n",
err, errno, retval, duration, size, sizeof(flow_keys));
CHECK_FLOW_KEYS("vlan_ipv4_flow_keys", flow_keys,
pkt_vlan_v4_flow_keys);
err = bpf_prog_test_run(prog_fd, 10, &pkt_vlan_v6, sizeof(pkt_vlan_v6),
&flow_keys, &size, &retval, &duration);
CHECK(size != sizeof(flow_keys) || err || retval != 1, "vlan_ipv6",
"err %d errno %d retval %d duration %d size %u/%lu\n",
err, errno, retval, duration, size, sizeof(flow_keys));
CHECK_FLOW_KEYS("vlan_ipv6_flow_keys", flow_keys,
pkt_vlan_v6_flow_keys);
bpf_object__close(obj);
}
......@@ -119,10 +119,7 @@ static __always_inline int parse_eth_proto(struct __sk_buff *skb, __be16 proto)
SEC("flow_dissector")
int _dissect(struct __sk_buff *skb)
{
if (!skb->vlan_present)
return parse_eth_proto(skb, skb->protocol);
else
return parse_eth_proto(skb, skb->vlan_proto);
return parse_eth_proto(skb, skb->protocol);
}
/* Parses on IPPROTO_* */
......@@ -336,15 +333,9 @@ PROG(VLAN)(struct __sk_buff *skb)
{
struct bpf_flow_keys *keys = skb->flow_keys;
struct vlan_hdr *vlan, _vlan;
__be16 proto;
/* Peek back to see if single or double-tagging */
if (bpf_skb_load_bytes(skb, keys->thoff - sizeof(proto), &proto,
sizeof(proto)))
return BPF_DROP;
/* Account for double-tagging */
if (proto == bpf_htons(ETH_P_8021AD)) {
if (keys->n_proto == bpf_htons(ETH_P_8021AD)) {
vlan = bpf_flow_dissect_get_header(skb, sizeof(*vlan), &_vlan);
if (!vlan)
return BPF_DROP;
......@@ -352,6 +343,7 @@ PROG(VLAN)(struct __sk_buff *skb)
if (vlan->h_vlan_encapsulated_proto != bpf_htons(ETH_P_8021Q))
return BPF_DROP;
keys->nhoff += sizeof(*vlan);
keys->thoff += sizeof(*vlan);
}
......@@ -359,6 +351,7 @@ PROG(VLAN)(struct __sk_buff *skb)
if (!vlan)
return BPF_DROP;
keys->nhoff += sizeof(*vlan);
keys->thoff += sizeof(*vlan);
/* Only allow 8021AD + 8021Q double tagging and no triple tagging.*/
if (vlan->h_vlan_encapsulated_proto == bpf_htons(ETH_P_8021AD) ||
......
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