// SPDX-License-Identifier: GPL-2.0 /* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */ #include "vmlinux.h" #include "bpf_tracing_net.h" #include <bpf/bpf_helpers.h> #include <bpf/bpf_endian.h> #define UDP_TEST_PORT 7777 void *bpf_cast_to_kern_ctx(void *) __ksym; bool init_csum_partial = false; bool final_csum_none = false; bool broken_csum_start = false; static unsigned int skb_headlen(const struct sk_buff *skb) { return skb->len - skb->data_len; } static unsigned int skb_headroom(const struct sk_buff *skb) { return skb->data - skb->head; } static int skb_checksum_start_offset(const struct sk_buff *skb) { return skb->csum_start - skb_headroom(skb); } SEC("tc") int decap_sanity(struct __sk_buff *skb) { struct sk_buff *kskb; struct ipv6hdr ip6h; struct udphdr udph; int err; if (skb->protocol != __bpf_constant_htons(ETH_P_IPV6)) return TC_ACT_SHOT; if (bpf_skb_load_bytes(skb, ETH_HLEN, &ip6h, sizeof(ip6h))) return TC_ACT_SHOT; if (ip6h.nexthdr != IPPROTO_UDP) return TC_ACT_SHOT; if (bpf_skb_load_bytes(skb, ETH_HLEN + sizeof(ip6h), &udph, sizeof(udph))) return TC_ACT_SHOT; if (udph.dest != __bpf_constant_htons(UDP_TEST_PORT)) return TC_ACT_SHOT; kskb = bpf_cast_to_kern_ctx(skb); init_csum_partial = (kskb->ip_summed == CHECKSUM_PARTIAL); err = bpf_skb_adjust_room(skb, -(s32)(ETH_HLEN + sizeof(ip6h) + sizeof(udph)), 1, BPF_F_ADJ_ROOM_FIXED_GSO); if (err) return TC_ACT_SHOT; final_csum_none = (kskb->ip_summed == CHECKSUM_NONE); if (kskb->ip_summed == CHECKSUM_PARTIAL && (unsigned int)skb_checksum_start_offset(kskb) >= skb_headlen(kskb)) broken_csum_start = true; return TC_ACT_SHOT; } char __license[] SEC("license") = "GPL";