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Helper function bpf_lwt_push_encap



Copyright (c) 2015 The Libbpf Authors. All rights reserved.

Encapsulate the packet associated to skb within a Layer 3 protocol header. This header is provided in the buffer at address hdr, with len its size in bytes. type indicates the protocol of the header and can be one of:


    IPv6 encapsulation with Segment Routing Header (struct ipv6_sr_hdr). hdr only contains the SRH, the IPv6 header is computed by the kernel.


    Only works if skb contains an IPv6 packet. Insert a Segment Routing Header (struct ipv6_sr_hdr) inside the IPv6 header.


    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 underlying packet buffer. Therefore, at load time, all checks on pointers previously done by the verifier are invalidated and must be performed again, if the helper is used in combination with direct packet access.


0 on success, or a negative error in case of failure.

static long (* const bpf_lwt_push_encap)(struct __sk_buff *skb, __u32 type, void *hdr, __u32 len) = (void *) 73;


Docs could be improved

This part of the docs is incomplete, contributions are very welcome

Program types

This helper call can be used in the following program types:


Docs could be improved

This part of the docs is incomplete, contributions are very welcome