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Commit 3e0bd37c authored by Peter Oskolkov's avatar Peter Oskolkov Committed by Alexei Starovoitov
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bpf: add plumbing for BPF_LWT_ENCAP_IP in bpf_lwt_push_encap 



This patch adds all needed plumbing in preparation to allowing
bpf programs to do IP encapping via bpf_lwt_push_encap. Actual
implementation is added in the next patch in the patchset.

Of note:
- bpf_lwt_push_encap can now be called from BPF_PROG_TYPE_LWT_XMIT
  prog types in addition to BPF_PROG_TYPE_LWT_IN;
- if the skb being encapped has GSO set, encapsulation is limited
  to IPIP/IP+GRE/IP+GUE (both IPv4 and IPv6);
- as route lookups are different for ingress vs egress, the single
  external bpf_lwt_push_encap BPF helper is routed internally to
  either bpf_lwt_in_push_encap or bpf_lwt_xmit_push_encap BPF_CALLs,
  depending on prog type.

v8 changes: fixed a typo.

Signed-off-by: default avatarPeter Oskolkov <posk@google.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent dd27c2e3

include/uapi/linux/bpf.h

+24 −2
Original line number Diff line number Diff line
@@ -2016,6 +2016,19 @@ union bpf_attr { 
 *			Only works if *skb* contains an IPv6 packet. Insert a

 *			Segment Routing Header (**struct ipv6_sr_hdr**) inside

 *			the IPv6 header.

 *		**BPF_LWT_ENCAP_IP**

 *			IP encapsulation (GRE/GUE/IPIP/etc). The outer header

 *			must be IPv4 or IPv6, followed by zero or more

 *			additional headers, up to LWT_BPF_MAX_HEADROOM total

 *			bytes in all prepended headers. Please note that

 *			if skb_is_gso(skb) is true, no more than two headers

 *			can be prepended, and the inner header, if present,

 *			should be either GRE or UDP/GUE.

 *

 *		BPF_LWT_ENCAP_SEG6*** types can be called by bpf programs of

 *		type BPF_PROG_TYPE_LWT_IN; BPF_LWT_ENCAP_IP type can be called

 *		by bpf programs of types BPF_PROG_TYPE_LWT_IN and

 *		BPF_PROG_TYPE_LWT_XMIT.

 *

 * 		A call to this helper is susceptible to change the underlaying

 * 		packet buffer. Therefore, at load time, all checks on pointers
@@ -2517,7 +2530,8 @@ enum bpf_hdr_start_off { 
/* Encapsulation type for BPF_FUNC_lwt_push_encap helper. */

enum bpf_lwt_encap_mode {

	BPF_LWT_ENCAP_SEG6,

	BPF_LWT_ENCAP_SEG6_INLINE

	BPF_LWT_ENCAP_SEG6_INLINE,

	BPF_LWT_ENCAP_IP,

};



#define __bpf_md_ptr(type, name)	\
@@ -2606,7 +2620,15 @@ enum bpf_ret_code { 
	BPF_DROP = 2,

	/* 3-6 reserved */

	BPF_REDIRECT = 7,

	/* >127 are reserved for prog type specific return codes */

	/* >127 are reserved for prog type specific return codes.

	 *

	 * BPF_LWT_REROUTE: used by BPF_PROG_TYPE_LWT_IN and

	 *    BPF_PROG_TYPE_LWT_XMIT to indicate that skb had been

	 *    changed and should be routed based on its new L3 header.

	 *    (This is an L3 redirect, as opposed to L2 redirect

	 *    represented by BPF_REDIRECT above).

	 */

	BPF_LWT_REROUTE = 128,

};



struct bpf_sock {

net/core/filter.c

+43 −5
Original line number Diff line number Diff line
@@ -4815,7 +4815,15 @@ static int bpf_push_seg6_encap(struct sk_buff *skb, u32 type, void *hdr, u32 len 
}

#endif /* CONFIG_IPV6_SEG6_BPF */



BPF_CALL_4(bpf_lwt_push_encap, struct sk_buff *, skb, u32, type, void *, hdr,

#if IS_ENABLED(CONFIG_LWTUNNEL_BPF)

static int bpf_push_ip_encap(struct sk_buff *skb, void *hdr, u32 len,

			     bool ingress)

{

	return -EINVAL;  /* Implemented in the next patch. */

}

#endif



BPF_CALL_4(bpf_lwt_in_push_encap, struct sk_buff *, skb, u32, type, void *, hdr,

	   u32, len)

{

	switch (type) {
@@ -4823,14 +4831,41 @@ BPF_CALL_4(bpf_lwt_push_encap, struct sk_buff *, skb, u32, type, void *, hdr, 
	case BPF_LWT_ENCAP_SEG6:

	case BPF_LWT_ENCAP_SEG6_INLINE:

		return bpf_push_seg6_encap(skb, type, hdr, len);

#endif

#if IS_ENABLED(CONFIG_LWTUNNEL_BPF)

	case BPF_LWT_ENCAP_IP:

		return bpf_push_ip_encap(skb, hdr, len, true /* ingress */);

#endif

	default:

		return -EINVAL;

	}

}



BPF_CALL_4(bpf_lwt_xmit_push_encap, struct sk_buff *, skb, u32, type,

	   void *, hdr, u32, len)

{

	switch (type) {

#if IS_ENABLED(CONFIG_LWTUNNEL_BPF)

	case BPF_LWT_ENCAP_IP:

		return bpf_push_ip_encap(skb, hdr, len, false /* egress */);

#endif

	default:

		return -EINVAL;

	}

}



static const struct bpf_func_proto bpf_lwt_push_encap_proto = {

	.func		= bpf_lwt_push_encap,

static const struct bpf_func_proto bpf_lwt_in_push_encap_proto = {

	.func		= bpf_lwt_in_push_encap,

	.gpl_only	= false,

	.ret_type	= RET_INTEGER,

	.arg1_type	= ARG_PTR_TO_CTX,

	.arg2_type	= ARG_ANYTHING,

	.arg3_type	= ARG_PTR_TO_MEM,

	.arg4_type	= ARG_CONST_SIZE

};



static const struct bpf_func_proto bpf_lwt_xmit_push_encap_proto = {

	.func		= bpf_lwt_xmit_push_encap,

	.gpl_only	= false,

	.ret_type	= RET_INTEGER,

	.arg1_type	= ARG_PTR_TO_CTX,
@@ -5417,7 +5452,8 @@ bool bpf_helper_changes_pkt_data(void *func) 
	    func == bpf_lwt_seg6_adjust_srh ||

	    func == bpf_lwt_seg6_action ||

#endif

	    func == bpf_lwt_push_encap)

	    func == bpf_lwt_in_push_encap ||

	    func == bpf_lwt_xmit_push_encap)

		return true;



	return false;
@@ -5815,7 +5851,7 @@ lwt_in_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) 
{

	switch (func_id) {

	case BPF_FUNC_lwt_push_encap:

		return &bpf_lwt_push_encap_proto;

		return &bpf_lwt_in_push_encap_proto;

	default:

		return lwt_out_func_proto(func_id, prog);

	}
@@ -5851,6 +5887,8 @@ lwt_xmit_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) 
		return &bpf_l4_csum_replace_proto;

	case BPF_FUNC_set_hash_invalid:

		return &bpf_set_hash_invalid_proto;

	case BPF_FUNC_lwt_push_encap:

		return &bpf_lwt_xmit_push_encap_proto;

	default:

		return lwt_out_func_proto(func_id, prog);

	}