Commit 0bc919d3 authored by Maciej Żenczykowski's avatar Maciej Żenczykowski Committed by Daniel Borkmann
Browse files

bpf: Support all gso types in bpf_skb_change_proto() 



Since we no longer modify gso_size, it is now theoretically
safe to not set SKB_GSO_DODGY and reset gso_segs to zero.

This also means the skb_is_gso_tcp() check should no longer
be necessary.

Unfortunately we cannot remove the skb_{decrease,increase}_gso_size()
helpers, as they are still used elsewhere:

  bpf_skb_net_grow() without BPF_F_ADJ_ROOM_FIXED_GSO
  bpf_skb_net_shrink() without BPF_F_ADJ_ROOM_FIXED_GSO
  net/core/lwt_bpf.c's handle_gso_type()

Signed-off-by: default avatarMaciej Żenczykowski <maze@google.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Cc: Dongseok Yi <dseok.yi@samsung.com>
Cc: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/bpf/20210617000953.2787453-3-zenczykowski@gmail.com
parent 364745fb

net/core/filter.c

+2 −20
Original line number Diff line number Diff line
@@ -3241,9 +3241,6 @@ static int bpf_skb_proto_4_to_6(struct sk_buff *skb) 
	u32 off = skb_mac_header_len(skb);

	int ret;



	if (skb_is_gso(skb) && !skb_is_gso_tcp(skb))

		return -ENOTSUPP;



	ret = skb_cow(skb, len_diff);

	if (unlikely(ret < 0))

		return ret;
@@ -3255,17 +3252,11 @@ static int bpf_skb_proto_4_to_6(struct sk_buff *skb) 
	if (skb_is_gso(skb)) {

		struct skb_shared_info *shinfo = skb_shinfo(skb);



		/* SKB_GSO_TCPV4 needs to be changed into

		 * SKB_GSO_TCPV6.

		 */

		/* SKB_GSO_TCPV4 needs to be changed into SKB_GSO_TCPV6. */

		if (shinfo->gso_type & SKB_GSO_TCPV4) {

			shinfo->gso_type &= ~SKB_GSO_TCPV4;

			shinfo->gso_type |=  SKB_GSO_TCPV6;

		}



		/* Header must be checked, and gso_segs recomputed. */

		shinfo->gso_type |= SKB_GSO_DODGY;

		shinfo->gso_segs = 0;

	}



	skb->protocol = htons(ETH_P_IPV6);
@@ -3280,9 +3271,6 @@ static int bpf_skb_proto_6_to_4(struct sk_buff *skb) 
	u32 off = skb_mac_header_len(skb);

	int ret;



	if (skb_is_gso(skb) && !skb_is_gso_tcp(skb))

		return -ENOTSUPP;



	ret = skb_unclone(skb, GFP_ATOMIC);

	if (unlikely(ret < 0))

		return ret;
@@ -3294,17 +3282,11 @@ static int bpf_skb_proto_6_to_4(struct sk_buff *skb) 
	if (skb_is_gso(skb)) {

		struct skb_shared_info *shinfo = skb_shinfo(skb);



		/* SKB_GSO_TCPV6 needs to be changed into

		 * SKB_GSO_TCPV4.

		 */

		/* SKB_GSO_TCPV6 needs to be changed into SKB_GSO_TCPV4. */

		if (shinfo->gso_type & SKB_GSO_TCPV6) {

			shinfo->gso_type &= ~SKB_GSO_TCPV6;

			shinfo->gso_type |=  SKB_GSO_TCPV4;

		}



		/* Header must be checked, and gso_segs recomputed. */

		shinfo->gso_type |= SKB_GSO_DODGY;

		shinfo->gso_segs = 0;

	}



	skb->protocol = htons(ETH_P_IP);