1*c313eae7SDaniel Xu // SPDX-License-Identifier: GPL-2.0-only
2*c313eae7SDaniel Xu #include "vmlinux.h"
3*c313eae7SDaniel Xu #include <bpf/bpf_helpers.h>
4*c313eae7SDaniel Xu #include <bpf/bpf_endian.h>
5*c313eae7SDaniel Xu #include "bpf_tracing_net.h"
6*c313eae7SDaniel Xu
7*c313eae7SDaniel Xu #define NF_DROP 0
8*c313eae7SDaniel Xu #define NF_ACCEPT 1
9*c313eae7SDaniel Xu #define ETH_P_IP 0x0800
10*c313eae7SDaniel Xu #define ETH_P_IPV6 0x86DD
11*c313eae7SDaniel Xu #define IP_MF 0x2000
12*c313eae7SDaniel Xu #define IP_OFFSET 0x1FFF
13*c313eae7SDaniel Xu #define NEXTHDR_FRAGMENT 44
14*c313eae7SDaniel Xu
15*c313eae7SDaniel Xu extern int bpf_dynptr_from_skb(struct sk_buff *skb, __u64 flags,
16*c313eae7SDaniel Xu struct bpf_dynptr *ptr__uninit) __ksym;
17*c313eae7SDaniel Xu extern void *bpf_dynptr_slice(const struct bpf_dynptr *ptr, uint32_t offset,
18*c313eae7SDaniel Xu void *buffer, uint32_t buffer__sz) __ksym;
19*c313eae7SDaniel Xu
20*c313eae7SDaniel Xu volatile int shootdowns = 0;
21*c313eae7SDaniel Xu
is_frag_v4(struct iphdr * iph)22*c313eae7SDaniel Xu static bool is_frag_v4(struct iphdr *iph)
23*c313eae7SDaniel Xu {
24*c313eae7SDaniel Xu int offset;
25*c313eae7SDaniel Xu int flags;
26*c313eae7SDaniel Xu
27*c313eae7SDaniel Xu offset = bpf_ntohs(iph->frag_off);
28*c313eae7SDaniel Xu flags = offset & ~IP_OFFSET;
29*c313eae7SDaniel Xu offset &= IP_OFFSET;
30*c313eae7SDaniel Xu offset <<= 3;
31*c313eae7SDaniel Xu
32*c313eae7SDaniel Xu return (flags & IP_MF) || offset;
33*c313eae7SDaniel Xu }
34*c313eae7SDaniel Xu
is_frag_v6(struct ipv6hdr * ip6h)35*c313eae7SDaniel Xu static bool is_frag_v6(struct ipv6hdr *ip6h)
36*c313eae7SDaniel Xu {
37*c313eae7SDaniel Xu /* Simplifying assumption that there are no extension headers
38*c313eae7SDaniel Xu * between fixed header and fragmentation header. This assumption
39*c313eae7SDaniel Xu * is only valid in this test case. It saves us the hassle of
40*c313eae7SDaniel Xu * searching all potential extension headers.
41*c313eae7SDaniel Xu */
42*c313eae7SDaniel Xu return ip6h->nexthdr == NEXTHDR_FRAGMENT;
43*c313eae7SDaniel Xu }
44*c313eae7SDaniel Xu
handle_v4(struct sk_buff * skb)45*c313eae7SDaniel Xu static int handle_v4(struct sk_buff *skb)
46*c313eae7SDaniel Xu {
47*c313eae7SDaniel Xu struct bpf_dynptr ptr;
48*c313eae7SDaniel Xu u8 iph_buf[20] = {};
49*c313eae7SDaniel Xu struct iphdr *iph;
50*c313eae7SDaniel Xu
51*c313eae7SDaniel Xu if (bpf_dynptr_from_skb(skb, 0, &ptr))
52*c313eae7SDaniel Xu return NF_DROP;
53*c313eae7SDaniel Xu
54*c313eae7SDaniel Xu iph = bpf_dynptr_slice(&ptr, 0, iph_buf, sizeof(iph_buf));
55*c313eae7SDaniel Xu if (!iph)
56*c313eae7SDaniel Xu return NF_DROP;
57*c313eae7SDaniel Xu
58*c313eae7SDaniel Xu /* Shootdown any frags */
59*c313eae7SDaniel Xu if (is_frag_v4(iph)) {
60*c313eae7SDaniel Xu shootdowns++;
61*c313eae7SDaniel Xu return NF_DROP;
62*c313eae7SDaniel Xu }
63*c313eae7SDaniel Xu
64*c313eae7SDaniel Xu return NF_ACCEPT;
65*c313eae7SDaniel Xu }
66*c313eae7SDaniel Xu
handle_v6(struct sk_buff * skb)67*c313eae7SDaniel Xu static int handle_v6(struct sk_buff *skb)
68*c313eae7SDaniel Xu {
69*c313eae7SDaniel Xu struct bpf_dynptr ptr;
70*c313eae7SDaniel Xu struct ipv6hdr *ip6h;
71*c313eae7SDaniel Xu u8 ip6h_buf[40] = {};
72*c313eae7SDaniel Xu
73*c313eae7SDaniel Xu if (bpf_dynptr_from_skb(skb, 0, &ptr))
74*c313eae7SDaniel Xu return NF_DROP;
75*c313eae7SDaniel Xu
76*c313eae7SDaniel Xu ip6h = bpf_dynptr_slice(&ptr, 0, ip6h_buf, sizeof(ip6h_buf));
77*c313eae7SDaniel Xu if (!ip6h)
78*c313eae7SDaniel Xu return NF_DROP;
79*c313eae7SDaniel Xu
80*c313eae7SDaniel Xu /* Shootdown any frags */
81*c313eae7SDaniel Xu if (is_frag_v6(ip6h)) {
82*c313eae7SDaniel Xu shootdowns++;
83*c313eae7SDaniel Xu return NF_DROP;
84*c313eae7SDaniel Xu }
85*c313eae7SDaniel Xu
86*c313eae7SDaniel Xu return NF_ACCEPT;
87*c313eae7SDaniel Xu }
88*c313eae7SDaniel Xu
89*c313eae7SDaniel Xu SEC("netfilter")
defrag(struct bpf_nf_ctx * ctx)90*c313eae7SDaniel Xu int defrag(struct bpf_nf_ctx *ctx)
91*c313eae7SDaniel Xu {
92*c313eae7SDaniel Xu struct sk_buff *skb = ctx->skb;
93*c313eae7SDaniel Xu
94*c313eae7SDaniel Xu switch (bpf_ntohs(skb->protocol)) {
95*c313eae7SDaniel Xu case ETH_P_IP:
96*c313eae7SDaniel Xu return handle_v4(skb);
97*c313eae7SDaniel Xu case ETH_P_IPV6:
98*c313eae7SDaniel Xu return handle_v6(skb);
99*c313eae7SDaniel Xu default:
100*c313eae7SDaniel Xu return NF_ACCEPT;
101*c313eae7SDaniel Xu }
102*c313eae7SDaniel Xu }
103*c313eae7SDaniel Xu
104*c313eae7SDaniel Xu char _license[] SEC("license") = "GPL";
105