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>

1 files changed, 19 insertions, 1 deletions

diff --git a/tools/testing/selftests/bpf/test_tc_tunnel.sh b/tools/testing/selftests/bpf/test_tc_tunnel.sh
index d4d8d5d3b06e..ff0d31d38061 100755
--- a/tools/testing/selftests/bpf/test_tc_tunnel.sh
+++ b/tools/testing/selftests/bpf/test_tc_tunnel.sh
@@ -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