From 7cdec54f9713256bb170873a1fc5c75c9127c9d2 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Tue, 2 Jun 2020 16:58:33 +0200 Subject: bpf: Add csum_level helper for fixing up csum levels Add a bpf_csum_level() helper which BPF programs can use in combination with bpf_skb_adjust_room() when they pass in BPF_F_ADJ_ROOM_NO_CSUM_RESET flag to the latter to avoid falling back to CHECKSUM_NONE. The bpf_csum_level() allows to adjust CHECKSUM_UNNECESSARY skb->csum_levels via BPF_CSUM_LEVEL_{INC,DEC} which calls __skb_{incr,decr}_checksum_unnecessary() on the skb. The helper also allows a BPF_CSUM_LEVEL_RESET which sets the skb's csum to CHECKSUM_NONE as well as a BPF_CSUM_LEVEL_QUERY to just return the current level. Without this helper, there is no way to otherwise adjust the skb->csum_level. I did not add an extra dummy flags as there is plenty of free bitspace in level argument itself iff ever needed in future. Signed-off-by: Daniel Borkmann Signed-off-by: Alexei Starovoitov Reviewed-by: Alan Maguire Acked-by: Lorenz Bauer Link: https://lore.kernel.org/bpf/279ae3717cb3d03c0ffeb511493c93c450a01e1a.1591108731.git.daniel@iogearbox.net --- include/uapi/linux/bpf.h | 43 ++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 42 insertions(+), 1 deletion(-) (limited to 'include/uapi') diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 3ba2bbbed80c..c65b374a5090 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -3220,6 +3220,38 @@ union bpf_attr { * calculation. * Return * Requested value, or 0, if flags are not recognized. + * + * int bpf_csum_level(struct sk_buff *skb, u64 level) + * Description + * Change the skbs checksum level by one layer up or down, or + * reset it entirely to none in order to have the stack perform + * checksum validation. The level is applicable to the following + * protocols: TCP, UDP, GRE, SCTP, FCOE. For example, a decap of + * | ETH | IP | UDP | GUE | IP | TCP | into | ETH | IP | TCP | + * through **bpf_skb_adjust_room**\ () helper with passing in + * **BPF_F_ADJ_ROOM_NO_CSUM_RESET** flag would require one call + * to **bpf_csum_level**\ () with **BPF_CSUM_LEVEL_DEC** since + * the UDP header is removed. Similarly, an encap of the latter + * into the former could be accompanied by a helper call to + * **bpf_csum_level**\ () with **BPF_CSUM_LEVEL_INC** if the + * skb is still intended to be processed in higher layers of the + * stack instead of just egressing at tc. + * + * There are three supported level settings at this time: + * + * * **BPF_CSUM_LEVEL_INC**: Increases skb->csum_level for skbs + * with CHECKSUM_UNNECESSARY. + * * **BPF_CSUM_LEVEL_DEC**: Decreases skb->csum_level for skbs + * with CHECKSUM_UNNECESSARY. + * * **BPF_CSUM_LEVEL_RESET**: Resets skb->csum_level to 0 and + * sets CHECKSUM_NONE to force checksum validation by the stack. + * * **BPF_CSUM_LEVEL_QUERY**: No-op, returns the current + * skb->csum_level. + * Return + * 0 on success, or a negative error in case of failure. In the + * case of **BPF_CSUM_LEVEL_QUERY**, the current skb->csum_level + * is returned or the error code -EACCES in case the skb is not + * subject to CHECKSUM_UNNECESSARY. */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -3356,7 +3388,8 @@ union bpf_attr { FN(ringbuf_reserve), \ FN(ringbuf_submit), \ FN(ringbuf_discard), \ - FN(ringbuf_query), + FN(ringbuf_query), \ + FN(csum_level), /* integer value in 'imm' field of BPF_CALL instruction selects which helper * function eBPF program intends to call @@ -3433,6 +3466,14 @@ enum { BPF_F_CURRENT_NETNS = (-1L), }; +/* BPF_FUNC_csum_level level values. */ +enum { + BPF_CSUM_LEVEL_QUERY, + BPF_CSUM_LEVEL_INC, + BPF_CSUM_LEVEL_DEC, + BPF_CSUM_LEVEL_RESET, +}; + /* BPF_FUNC_skb_adjust_room flags. */ enum { BPF_F_ADJ_ROOM_FIXED_GSO = (1ULL << 0), -- cgit v1.2.3-59-g8ed1b