--- /dev/null
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2022 Felix Fietkau <nbd@nbd.name>
+ */
+#ifndef __BPF_SKB_UTILS_H
+#define __BPF_SKB_UTILS_H
+
+#include <uapi/linux/bpf.h>
+#include <uapi/linux/if_ether.h>
+#include <uapi/linux/ip.h>
+#include <uapi/linux/ipv6.h>
+#include <linux/ip.h>
+#include <net/ipv6.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_endian.h>
+
+struct skb_parser_info {
+ struct __sk_buff *skb;
+ __u32 offset;
+ int proto;
+};
+
+static __always_inline void *__skb_data(struct __sk_buff *skb)
+{
+ return (void *)(long)READ_ONCE(skb->data);
+}
+
+static __always_inline void *
+skb_ptr(struct __sk_buff *skb, __u32 offset, __u32 len)
+{
+ void *ptr = __skb_data(skb) + offset;
+ void *end = (void *)(long)(skb->data_end);
+
+ if (ptr + len >= end)
+ return NULL;
+
+ return ptr;
+}
+
+static __always_inline void *
+skb_info_ptr(struct skb_parser_info *info, __u32 len)
+{
+ __u32 offset = info->offset;
+ return skb_ptr(info->skb, offset, len);
+}
+
+static __always_inline void
+skb_parse_init(struct skb_parser_info *info, struct __sk_buff *skb)
+{
+ *info = (struct skb_parser_info){
+ .skb = skb
+ };
+}
+
+static __always_inline struct ethhdr *
+skb_parse_ethernet(struct skb_parser_info *info)
+{
+ struct ethhdr *eth;
+
+ eth = skb_info_ptr(info, sizeof(*eth));
+ if (!eth)
+ return NULL;
+
+ info->proto = eth->h_proto;
+ info->offset += sizeof(*eth);
+
+ return eth;
+}
+
+static __always_inline struct vlan_hdr *
+skb_parse_vlan(struct skb_parser_info *info)
+{
+ struct vlan_hdr *vlh;
+
+ if (info->proto != bpf_htons(ETH_P_8021Q) &&
+ info->proto != bpf_htons(ETH_P_8021AD))
+ return NULL;
+
+ vlh = skb_info_ptr(info, sizeof(*vlh));
+ if (!vlh)
+ return NULL;
+
+ info->proto = vlh->h_vlan_encapsulated_proto;
+ info->offset += sizeof(*vlh);
+
+ return vlh;
+}
+
+static __always_inline struct iphdr *
+skb_parse_ipv4(struct skb_parser_info *info, int min_l4_bytes)
+{
+ struct iphdr *iph;
+ int proto, hdr_len;
+ __u32 pull_len;
+
+ if (info->proto != bpf_htons(ETH_P_IP))
+ return NULL;
+
+ iph = skb_info_ptr(info, sizeof(*iph));
+ if (!iph)
+ return NULL;
+
+ hdr_len = iph->ihl * 4;
+ if (hdr_len < sizeof(*iph))
+ return NULL;
+
+ pull_len = info->offset + hdr_len + min_l4_bytes;
+ if (pull_len > info->skb->len)
+ pull_len = info->skb->len;
+
+ if (bpf_skb_pull_data(info->skb, pull_len))
+ return NULL;
+
+ iph = skb_info_ptr(info, sizeof(*iph));
+ if (!iph)
+ return NULL;
+
+ info->proto = iph->protocol;
+ info->offset += hdr_len;
+
+ return iph;
+}
+
+static __always_inline struct ipv6hdr *
+skb_parse_ipv6(struct skb_parser_info *info, int max_l4_bytes)
+{
+ struct ipv6hdr *ip6h;
+ __u32 pull_len;
+
+ if (info->proto != bpf_htons(ETH_P_IPV6))
+ return NULL;
+
+ pull_len = info->offset + sizeof(*ip6h) + max_l4_bytes;
+ if (pull_len > info->skb->len)
+ pull_len = info->skb->len;
+
+ if (bpf_skb_pull_data(info->skb, pull_len))
+ return NULL;
+
+ ip6h = skb_info_ptr(info, sizeof(*ip6h));
+ if (!ip6h)
+ return NULL;
+
+ info->proto = READ_ONCE(ip6h->nexthdr);
+ info->offset += sizeof(*ip6h);
+
+ return ip6h;
+}
+
+static __always_inline struct tcphdr *
+skb_parse_tcp(struct skb_parser_info *info)
+{
+ struct tcphdr *tcph;
+
+ if (info->proto != IPPROTO_TCP)
+ return NULL;
+
+ tcph = skb_info_ptr(info, sizeof(*tcph));
+ if (!tcph)
+ return NULL;
+
+ info->offset += tcph->doff * 4;
+
+ return tcph;
+}
+
+#endif