[PATCH bpf-next v3 11/13] selftests/bpf: convert bpf tunnel test to BPF_ADJ_ROOM_MAC

[Willem de Bruijn]

From: Willem de Bruijn <will...@google.com>

Avoid moving the network layer header when prefixing tunnel headers.

This avoids an explicit call to bpf_skb_store_bytes and an implicit
move of the network header bytes in bpf_skb_adjust_room.

Signed-off-by: Willem de Bruijn <will...@google.com>
---
 .../selftests/bpf/progs/test_tc_tunnel.c      | 25 +++----------------
 1 file changed, 3 insertions(+), 22 deletions(-)

diff --git a/tools/testing/selftests/bpf/progs/test_tc_tunnel.c 
b/tools/testing/selftests/bpf/progs/test_tc_tunnel.c
index 900c5653105f..f6a16fd23dbd 100644
--- a/tools/testing/selftests/bpf/progs/test_tc_tunnel.c
+++ b/tools/testing/selftests/bpf/progs/test_tc_tunnel.c
@@ -72,7 +72,7 @@ static __always_inline int encap_ipv4(struct __sk_buff *skb, 
bool with_gre)
        olen = with_gre ? sizeof(h_outer) : sizeof(h_outer.ip);
 
        /* add room between mac and network header */
-       if (bpf_skb_adjust_room(skb, olen, BPF_ADJ_ROOM_NET, 0))
+       if (bpf_skb_adjust_room(skb, olen, BPF_ADJ_ROOM_MAC, 0))
                return TC_ACT_SHOT;
 
        /* prepare new outer network header */
@@ -94,12 +94,6 @@ static __always_inline int encap_ipv4(struct __sk_buff *skb, 
bool with_gre)
                                BPF_F_INVALIDATE_HASH) < 0)
                return TC_ACT_SHOT;
 
-       /* bpf_skb_adjust_room has moved header to start of room: restore */
-       if (bpf_skb_store_bytes(skb, ETH_HLEN + olen,
-                               &iph_inner, sizeof(iph_inner),
-                               BPF_F_INVALIDATE_HASH) < 0)
-               return TC_ACT_SHOT;
-
        return TC_ACT_OK;
 }
 
@@ -125,7 +119,7 @@ static __always_inline int encap_ipv6(struct __sk_buff 
*skb, bool with_gre)
        olen = with_gre ? sizeof(h_outer) : sizeof(h_outer.ip);
 
        /* add room between mac and network header */
-       if (bpf_skb_adjust_room(skb, olen, BPF_ADJ_ROOM_NET, 0))
+       if (bpf_skb_adjust_room(skb, olen, BPF_ADJ_ROOM_MAC, 0))
                return TC_ACT_SHOT;
 
        /* prepare new outer network header */
@@ -145,12 +139,6 @@ static __always_inline int encap_ipv6(struct __sk_buff 
*skb, bool with_gre)
                                BPF_F_INVALIDATE_HASH) < 0)
                return TC_ACT_SHOT;
 
-       /* bpf_skb_adjust_room has moved header to start of room: restore */
-       if (bpf_skb_store_bytes(skb, ETH_HLEN + olen,
-                               &iph_inner, sizeof(iph_inner),
-                               BPF_F_INVALIDATE_HASH) < 0)
-               return TC_ACT_SHOT;
-
        return TC_ACT_OK;
 }
 
@@ -207,14 +195,7 @@ static int decap_internal(struct __sk_buff *skb, int off, 
int len, char proto)
                return TC_ACT_OK;
        }
 
-       if (bpf_skb_load_bytes(skb, off + olen, &buf, olen) < 0)
-               return TC_ACT_OK;
-
-       if (bpf_skb_adjust_room(skb, -olen, BPF_ADJ_ROOM_NET, 0))
-               return TC_ACT_SHOT;
-
-       /* bpf_skb_adjust_room has moved outer over inner header: restore */
-       if (bpf_skb_store_bytes(skb, off, buf, len, BPF_F_INVALIDATE_HASH) < 0)
+       if (bpf_skb_adjust_room(skb, -olen, BPF_ADJ_ROOM_MAC, 0))
                return TC_ACT_SHOT;
 
        return TC_ACT_OK;
-- 
2.21.0.392.gf8f6787159e-goog