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