bpf: Add bpf_skb_adjust_room flag BPF_F_ADJ_ROOM_ENCAP_L2_ETH

bpf_skb_adjust_room sets the inner_protocol as skb->protocol for packets
encapsulation. But that is not appropriate when pushing Ethernet header.

Add an option to further specify encap L2 type and set the inner_protocol
as ETH_P_TEB.

Suggested-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Xuesen Huang <huangxuesen@kuaishou.com>
Signed-off-by: Zhiyong Cheng <chengzhiyong@kuaishou.com>
Signed-off-by: Li Wang <wangli09@kuaishou.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/bpf/20210304064046.6232-1-hxseverything@gmail.com

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 7f530e3..2d3036e 100644 (file)
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -2484,6 +2484,10 @@ union bpf_attr {
  *               Use with ENCAP_L3/L4 flags to further specify the tunnel
  *               type; *len* is the length of the inner MAC header.
  *
+ *             * **BPF_F_ADJ_ROOM_ENCAP_L2_ETH**:
+ *               Use with BPF_F_ADJ_ROOM_ENCAP_L2 flag to further specify the
+ *               L2 type as Ethernet.
+ *
  *             A call to this helper is susceptible to change the underlying
  *             packet buffer. Therefore, at load time, all checks on pointers
  *             previously done by the verifier are invalidated and must be
@@ -4916,6 +4920,7 @@ enum {
        BPF_F_ADJ_ROOM_ENCAP_L4_GRE     = (1ULL << 3),
        BPF_F_ADJ_ROOM_ENCAP_L4_UDP     = (1ULL << 4),
        BPF_F_ADJ_ROOM_NO_CSUM_RESET    = (1ULL << 5),
+       BPF_F_ADJ_ROOM_ENCAP_L2_ETH     = (1ULL << 6),
 };
 
 enum {

diff --git a/net/core/filter.c b/net/core/filter.c
index a526db4..588b19b 100644 (file)
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3409,6 +3409,7 @@ static u32 bpf_skb_net_base_len(const struct sk_buff *skb)
                                         BPF_F_ADJ_ROOM_ENCAP_L3_MASK | \
                                         BPF_F_ADJ_ROOM_ENCAP_L4_GRE | \
                                         BPF_F_ADJ_ROOM_ENCAP_L4_UDP | \
+                                        BPF_F_ADJ_ROOM_ENCAP_L2_ETH | \
                                         BPF_F_ADJ_ROOM_ENCAP_L2( \
                                          BPF_ADJ_ROOM_ENCAP_L2_MASK))
 
@@ -3445,6 +3446,10 @@ static int bpf_skb_net_grow(struct sk_buff *skb, u32 off, u32 len_diff,
                    flags & BPF_F_ADJ_ROOM_ENCAP_L4_UDP)
                        return -EINVAL;
 
+               if (flags & BPF_F_ADJ_ROOM_ENCAP_L2_ETH &&
+                   inner_mac_len < ETH_HLEN)
+                       return -EINVAL;
+
                if (skb->encapsulation)
                        return -EALREADY;
 
@@ -3463,7 +3468,11 @@ static int bpf_skb_net_grow(struct sk_buff *skb, u32 off, u32 len_diff,
                skb->inner_mac_header = inner_net - inner_mac_len;
                skb->inner_network_header = inner_net;
                skb->inner_transport_header = inner_trans;
-               skb_set_inner_protocol(skb, skb->protocol);
+
+               if (flags & BPF_F_ADJ_ROOM_ENCAP_L2_ETH)
+                       skb_set_inner_protocol(skb, htons(ETH_P_TEB));
+               else
+                       skb_set_inner_protocol(skb, skb->protocol);
 
                skb->encapsulation = 1;
                skb_set_network_header(skb, mac_len);

diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 7f530e3..2d3036e 100644 (file)
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -2484,6 +2484,10 @@ union bpf_attr {
  *               Use with ENCAP_L3/L4 flags to further specify the tunnel
  *               type; *len* is the length of the inner MAC header.
  *
+ *             * **BPF_F_ADJ_ROOM_ENCAP_L2_ETH**:
+ *               Use with BPF_F_ADJ_ROOM_ENCAP_L2 flag to further specify the
+ *               L2 type as Ethernet.
+ *
  *             A call to this helper is susceptible to change the underlying
  *             packet buffer. Therefore, at load time, all checks on pointers
  *             previously done by the verifier are invalidated and must be
@@ -4916,6 +4920,7 @@ enum {
        BPF_F_ADJ_ROOM_ENCAP_L4_GRE     = (1ULL << 3),
        BPF_F_ADJ_ROOM_ENCAP_L4_UDP     = (1ULL << 4),
        BPF_F_ADJ_ROOM_NO_CSUM_RESET    = (1ULL << 5),
+       BPF_F_ADJ_ROOM_ENCAP_L2_ETH     = (1ULL << 6),
 };
 
 enum {