selftests/bpf: expand test_tc_tunnel with SIT encap

So far, all BPF tc tunnel testcases encapsulate in the same network
protocol. Add an encap testcase that requires updating skb->protocol.

The 6in4 tunnel encapsulates an IPv6 packet inside an IPv4 tunnel.
Verify that bpf_skb_net_grow correctly updates skb->protocol to
select the right protocol handler in __netif_receive_skb_core.

The BPF program should also manually update the link layer header to
encode the right network protocol.

Changes v1->v2
  - improve documentation of non-obvious logic

Signed-off-by: Willem de Bruijn <willemb@google.com>
Tested-by: Alan Maguire <alan.maguire@oracle.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Willem de Bruijn 2019-04-23 14:43:49 -04:00 committed by Daniel Borkmann
parent 1b00e0dfe7
commit f6ad6accaa
3 changed files with 80 additions and 5 deletions

View File

@ -33,3 +33,4 @@ CONFIG_MPLS=y
CONFIG_NET_MPLS_GSO=m
CONFIG_MPLS_ROUTING=m
CONFIG_MPLS_IPTUNNEL=m
CONFIG_IPV6_SIT=m

View File

@ -77,17 +77,52 @@ static __always_inline int encap_ipv4(struct __sk_buff *skb, __u8 encap_proto,
struct v4hdr h_outer;
struct tcphdr tcph;
int olen, l2_len;
int tcp_off;
__u64 flags;
if (bpf_skb_load_bytes(skb, ETH_HLEN, &iph_inner,
sizeof(iph_inner)) < 0)
return TC_ACT_OK;
/* Most tests encapsulate a packet into a tunnel with the same
* network protocol, and derive the outer header fields from
* the inner header.
*
* The 6in4 case tests different inner and outer protocols. As
* the inner is ipv6, but the outer expects an ipv4 header as
* input, manually build a struct iphdr based on the ipv6hdr.
*/
if (encap_proto == IPPROTO_IPV6) {
const __u32 saddr = (192 << 24) | (168 << 16) | (1 << 8) | 1;
const __u32 daddr = (192 << 24) | (168 << 16) | (1 << 8) | 2;
struct ipv6hdr iph6_inner;
/* Read the IPv6 header */
if (bpf_skb_load_bytes(skb, ETH_HLEN, &iph6_inner,
sizeof(iph6_inner)) < 0)
return TC_ACT_OK;
/* Derive the IPv4 header fields from the IPv6 header */
memset(&iph_inner, 0, sizeof(iph_inner));
iph_inner.version = 4;
iph_inner.ihl = 5;
iph_inner.tot_len = bpf_htons(sizeof(iph6_inner) +
bpf_ntohs(iph6_inner.payload_len));
iph_inner.ttl = iph6_inner.hop_limit - 1;
iph_inner.protocol = iph6_inner.nexthdr;
iph_inner.saddr = __bpf_constant_htonl(saddr);
iph_inner.daddr = __bpf_constant_htonl(daddr);
tcp_off = sizeof(iph6_inner);
} else {
if (bpf_skb_load_bytes(skb, ETH_HLEN, &iph_inner,
sizeof(iph_inner)) < 0)
return TC_ACT_OK;
tcp_off = sizeof(iph_inner);
}
/* filter only packets we want */
if (iph_inner.ihl != 5 || iph_inner.protocol != IPPROTO_TCP)
return TC_ACT_OK;
if (bpf_skb_load_bytes(skb, ETH_HLEN + sizeof(iph_inner),
if (bpf_skb_load_bytes(skb, ETH_HLEN + tcp_off,
&tcph, sizeof(tcph)) < 0)
return TC_ACT_OK;
@ -129,6 +164,7 @@ static __always_inline int encap_ipv4(struct __sk_buff *skb, __u8 encap_proto,
l2_len);
break;
case IPPROTO_IPIP:
case IPPROTO_IPV6:
break;
default:
return TC_ACT_OK;
@ -164,6 +200,17 @@ static __always_inline int encap_ipv4(struct __sk_buff *skb, __u8 encap_proto,
BPF_F_INVALIDATE_HASH) < 0)
return TC_ACT_SHOT;
/* if changing outer proto type, update eth->h_proto */
if (encap_proto == IPPROTO_IPV6) {
struct ethhdr eth;
if (bpf_skb_load_bytes(skb, 0, &eth, sizeof(eth)) < 0)
return TC_ACT_SHOT;
eth.h_proto = bpf_htons(ETH_P_IP);
if (bpf_skb_store_bytes(skb, 0, &eth, sizeof(eth), 0) < 0)
return TC_ACT_SHOT;
}
return TC_ACT_OK;
}
@ -325,6 +372,15 @@ int __encap_udp_eth(struct __sk_buff *skb)
return TC_ACT_OK;
}
SEC("encap_sit_none")
int __encap_sit_none(struct __sk_buff *skb)
{
if (skb->protocol == __bpf_constant_htons(ETH_P_IPV6))
return encap_ipv4(skb, IPPROTO_IPV6, ETH_P_IP);
else
return TC_ACT_OK;
}
SEC("encap_ip6tnl_none")
int __encap_ip6tnl_none(struct __sk_buff *skb)
{

View File

@ -97,6 +97,9 @@ if [[ "$#" -eq "0" ]]; then
echo "ip6ip6"
$0 ipv6 ip6tnl none 100
echo "sit"
$0 ipv6 sit none 100
for mac in none mpls eth ; do
echo "ip gre $mac"
$0 ipv4 gre $mac 100
@ -211,11 +214,20 @@ else
targs=""
fi
# tunnel address family differs from inner for SIT
if [[ "${tuntype}" == "sit" ]]; then
link_addr1="${ns1_v4}"
link_addr2="${ns2_v4}"
else
link_addr1="${addr1}"
link_addr2="${addr2}"
fi
# serverside, insert decap module
# server is still running
# client can connect again
ip netns exec "${ns2}" ip link add name testtun0 type "${ttype}" \
${tmode} remote "${addr1}" local "${addr2}" $targs
${tmode} remote "${link_addr1}" local "${link_addr2}" $targs
expect_tun_fail=0
@ -260,6 +272,12 @@ else
server_listen
fi
# bpf_skb_net_shrink does not take tunnel flags yet, cannot update L3.
if [[ "${tuntype}" == "sit" ]]; then
echo OK
exit 0
fi
# serverside, use BPF for decap
ip netns exec "${ns2}" ip link del dev testtun0
ip netns exec "${ns2}" tc qdisc add dev veth2 clsact