438 lines
11 KiB
C
438 lines
11 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <limits.h>
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#include <stddef.h>
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#include <stdbool.h>
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#include <string.h>
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#include <linux/pkt_cls.h>
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#include <linux/bpf.h>
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#include <linux/in.h>
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#include <linux/if_ether.h>
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#include <linux/icmp.h>
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#include <linux/ip.h>
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#include <linux/ipv6.h>
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#include <linux/tcp.h>
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#include <linux/udp.h>
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#include <linux/if_packet.h>
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#include <sys/socket.h>
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#include <linux/if_tunnel.h>
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#include <linux/mpls.h>
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#include <bpf/bpf_helpers.h>
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#include <bpf/bpf_endian.h>
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#define PROG(F) PROG_(F, _##F)
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#define PROG_(NUM, NAME) SEC("flow_dissector") int flow_dissector_##NUM
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#define FLOW_CONTINUE_SADDR 0x7f00007f /* 127.0.0.127 */
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/* These are the identifiers of the BPF programs that will be used in tail
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* calls. Name is limited to 16 characters, with the terminating character and
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* bpf_func_ above, we have only 6 to work with, anything after will be cropped.
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*/
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#define IP 0
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#define IPV6 1
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#define IPV6OP 2 /* Destination/Hop-by-Hop Options IPv6 Ext. Header */
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#define IPV6FR 3 /* Fragmentation IPv6 Extension Header */
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#define MPLS 4
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#define VLAN 5
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#define MAX_PROG 6
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#define IP_MF 0x2000
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#define IP_OFFSET 0x1FFF
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#define IP6_MF 0x0001
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#define IP6_OFFSET 0xFFF8
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struct vlan_hdr {
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__be16 h_vlan_TCI;
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__be16 h_vlan_encapsulated_proto;
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};
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struct gre_hdr {
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__be16 flags;
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__be16 proto;
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};
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struct frag_hdr {
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__u8 nexthdr;
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__u8 reserved;
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__be16 frag_off;
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__be32 identification;
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};
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struct {
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__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
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__uint(max_entries, MAX_PROG);
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__uint(key_size, sizeof(__u32));
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__uint(value_size, sizeof(__u32));
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} jmp_table SEC(".maps");
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struct {
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__uint(type, BPF_MAP_TYPE_HASH);
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__uint(max_entries, 1024);
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__type(key, __u32);
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__type(value, struct bpf_flow_keys);
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} last_dissection SEC(".maps");
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static __always_inline int export_flow_keys(struct bpf_flow_keys *keys,
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int ret)
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{
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__u32 key = (__u32)(keys->sport) << 16 | keys->dport;
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struct bpf_flow_keys val;
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memcpy(&val, keys, sizeof(val));
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bpf_map_update_elem(&last_dissection, &key, &val, BPF_ANY);
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return ret;
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}
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#define IPV6_FLOWLABEL_MASK __bpf_constant_htonl(0x000FFFFF)
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static inline __be32 ip6_flowlabel(const struct ipv6hdr *hdr)
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{
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return *(__be32 *)hdr & IPV6_FLOWLABEL_MASK;
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}
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static __always_inline void *bpf_flow_dissect_get_header(struct __sk_buff *skb,
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__u16 hdr_size,
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void *buffer)
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{
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void *data_end = (void *)(long)skb->data_end;
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void *data = (void *)(long)skb->data;
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__u16 thoff = skb->flow_keys->thoff;
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__u8 *hdr;
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/* Verifies this variable offset does not overflow */
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if (thoff > (USHRT_MAX - hdr_size))
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return NULL;
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hdr = data + thoff;
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if (hdr + hdr_size <= data_end)
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return hdr;
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if (bpf_skb_load_bytes(skb, thoff, buffer, hdr_size))
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return NULL;
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return buffer;
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}
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/* Dispatches on ETHERTYPE */
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static __always_inline int parse_eth_proto(struct __sk_buff *skb, __be16 proto)
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{
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struct bpf_flow_keys *keys = skb->flow_keys;
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switch (proto) {
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case bpf_htons(ETH_P_IP):
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bpf_tail_call_static(skb, &jmp_table, IP);
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break;
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case bpf_htons(ETH_P_IPV6):
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bpf_tail_call_static(skb, &jmp_table, IPV6);
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break;
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case bpf_htons(ETH_P_MPLS_MC):
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case bpf_htons(ETH_P_MPLS_UC):
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bpf_tail_call_static(skb, &jmp_table, MPLS);
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break;
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case bpf_htons(ETH_P_8021Q):
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case bpf_htons(ETH_P_8021AD):
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bpf_tail_call_static(skb, &jmp_table, VLAN);
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break;
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default:
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/* Protocol not supported */
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return export_flow_keys(keys, BPF_DROP);
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}
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return export_flow_keys(keys, BPF_DROP);
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}
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SEC("flow_dissector")
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int _dissect(struct __sk_buff *skb)
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{
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struct bpf_flow_keys *keys = skb->flow_keys;
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if (keys->n_proto == bpf_htons(ETH_P_IP)) {
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/* IP traffic from FLOW_CONTINUE_SADDR falls-back to
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* standard dissector
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*/
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struct iphdr *iph, _iph;
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iph = bpf_flow_dissect_get_header(skb, sizeof(*iph), &_iph);
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if (iph && iph->ihl == 5 &&
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iph->saddr == bpf_htonl(FLOW_CONTINUE_SADDR)) {
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return BPF_FLOW_DISSECTOR_CONTINUE;
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}
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}
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return parse_eth_proto(skb, keys->n_proto);
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}
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/* Parses on IPPROTO_* */
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static __always_inline int parse_ip_proto(struct __sk_buff *skb, __u8 proto)
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{
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struct bpf_flow_keys *keys = skb->flow_keys;
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void *data_end = (void *)(long)skb->data_end;
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struct icmphdr *icmp, _icmp;
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struct gre_hdr *gre, _gre;
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struct ethhdr *eth, _eth;
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struct tcphdr *tcp, _tcp;
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struct udphdr *udp, _udp;
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switch (proto) {
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case IPPROTO_ICMP:
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icmp = bpf_flow_dissect_get_header(skb, sizeof(*icmp), &_icmp);
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if (!icmp)
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return export_flow_keys(keys, BPF_DROP);
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return export_flow_keys(keys, BPF_OK);
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case IPPROTO_IPIP:
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keys->is_encap = true;
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if (keys->flags & BPF_FLOW_DISSECTOR_F_STOP_AT_ENCAP)
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return export_flow_keys(keys, BPF_OK);
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return parse_eth_proto(skb, bpf_htons(ETH_P_IP));
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case IPPROTO_IPV6:
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keys->is_encap = true;
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if (keys->flags & BPF_FLOW_DISSECTOR_F_STOP_AT_ENCAP)
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return export_flow_keys(keys, BPF_OK);
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return parse_eth_proto(skb, bpf_htons(ETH_P_IPV6));
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case IPPROTO_GRE:
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gre = bpf_flow_dissect_get_header(skb, sizeof(*gre), &_gre);
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if (!gre)
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return export_flow_keys(keys, BPF_DROP);
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if (bpf_htons(gre->flags & GRE_VERSION))
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/* Only inspect standard GRE packets with version 0 */
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return export_flow_keys(keys, BPF_OK);
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keys->thoff += sizeof(*gre); /* Step over GRE Flags and Proto */
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if (GRE_IS_CSUM(gre->flags))
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keys->thoff += 4; /* Step over chksum and Padding */
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if (GRE_IS_KEY(gre->flags))
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keys->thoff += 4; /* Step over key */
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if (GRE_IS_SEQ(gre->flags))
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keys->thoff += 4; /* Step over sequence number */
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keys->is_encap = true;
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if (keys->flags & BPF_FLOW_DISSECTOR_F_STOP_AT_ENCAP)
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return export_flow_keys(keys, BPF_OK);
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if (gre->proto == bpf_htons(ETH_P_TEB)) {
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eth = bpf_flow_dissect_get_header(skb, sizeof(*eth),
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&_eth);
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if (!eth)
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return export_flow_keys(keys, BPF_DROP);
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keys->thoff += sizeof(*eth);
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return parse_eth_proto(skb, eth->h_proto);
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} else {
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return parse_eth_proto(skb, gre->proto);
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}
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case IPPROTO_TCP:
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tcp = bpf_flow_dissect_get_header(skb, sizeof(*tcp), &_tcp);
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if (!tcp)
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return export_flow_keys(keys, BPF_DROP);
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if (tcp->doff < 5)
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return export_flow_keys(keys, BPF_DROP);
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if ((__u8 *)tcp + (tcp->doff << 2) > data_end)
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return export_flow_keys(keys, BPF_DROP);
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keys->sport = tcp->source;
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keys->dport = tcp->dest;
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return export_flow_keys(keys, BPF_OK);
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case IPPROTO_UDP:
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case IPPROTO_UDPLITE:
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udp = bpf_flow_dissect_get_header(skb, sizeof(*udp), &_udp);
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if (!udp)
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return export_flow_keys(keys, BPF_DROP);
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keys->sport = udp->source;
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keys->dport = udp->dest;
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return export_flow_keys(keys, BPF_OK);
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default:
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return export_flow_keys(keys, BPF_DROP);
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}
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return export_flow_keys(keys, BPF_DROP);
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}
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static __always_inline int parse_ipv6_proto(struct __sk_buff *skb, __u8 nexthdr)
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{
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struct bpf_flow_keys *keys = skb->flow_keys;
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switch (nexthdr) {
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case IPPROTO_HOPOPTS:
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case IPPROTO_DSTOPTS:
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bpf_tail_call_static(skb, &jmp_table, IPV6OP);
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break;
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case IPPROTO_FRAGMENT:
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bpf_tail_call_static(skb, &jmp_table, IPV6FR);
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break;
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default:
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return parse_ip_proto(skb, nexthdr);
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}
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return export_flow_keys(keys, BPF_DROP);
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}
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PROG(IP)(struct __sk_buff *skb)
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{
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void *data_end = (void *)(long)skb->data_end;
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struct bpf_flow_keys *keys = skb->flow_keys;
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void *data = (void *)(long)skb->data;
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struct iphdr *iph, _iph;
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bool done = false;
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iph = bpf_flow_dissect_get_header(skb, sizeof(*iph), &_iph);
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if (!iph)
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return export_flow_keys(keys, BPF_DROP);
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/* IP header cannot be smaller than 20 bytes */
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if (iph->ihl < 5)
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return export_flow_keys(keys, BPF_DROP);
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keys->addr_proto = ETH_P_IP;
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keys->ipv4_src = iph->saddr;
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keys->ipv4_dst = iph->daddr;
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keys->ip_proto = iph->protocol;
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keys->thoff += iph->ihl << 2;
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if (data + keys->thoff > data_end)
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return export_flow_keys(keys, BPF_DROP);
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if (iph->frag_off & bpf_htons(IP_MF | IP_OFFSET)) {
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keys->is_frag = true;
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if (iph->frag_off & bpf_htons(IP_OFFSET)) {
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/* From second fragment on, packets do not have headers
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* we can parse.
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*/
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done = true;
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} else {
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keys->is_first_frag = true;
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/* No need to parse fragmented packet unless
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* explicitly asked for.
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*/
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if (!(keys->flags &
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BPF_FLOW_DISSECTOR_F_PARSE_1ST_FRAG))
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done = true;
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}
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}
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if (done)
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return export_flow_keys(keys, BPF_OK);
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return parse_ip_proto(skb, iph->protocol);
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}
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PROG(IPV6)(struct __sk_buff *skb)
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{
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struct bpf_flow_keys *keys = skb->flow_keys;
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struct ipv6hdr *ip6h, _ip6h;
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ip6h = bpf_flow_dissect_get_header(skb, sizeof(*ip6h), &_ip6h);
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if (!ip6h)
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return export_flow_keys(keys, BPF_DROP);
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keys->addr_proto = ETH_P_IPV6;
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memcpy(&keys->ipv6_src, &ip6h->saddr, 2*sizeof(ip6h->saddr));
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keys->thoff += sizeof(struct ipv6hdr);
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keys->ip_proto = ip6h->nexthdr;
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keys->flow_label = ip6_flowlabel(ip6h);
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if (keys->flags & BPF_FLOW_DISSECTOR_F_STOP_AT_FLOW_LABEL)
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return export_flow_keys(keys, BPF_OK);
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return parse_ipv6_proto(skb, ip6h->nexthdr);
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}
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PROG(IPV6OP)(struct __sk_buff *skb)
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{
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struct bpf_flow_keys *keys = skb->flow_keys;
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struct ipv6_opt_hdr *ip6h, _ip6h;
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ip6h = bpf_flow_dissect_get_header(skb, sizeof(*ip6h), &_ip6h);
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if (!ip6h)
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return export_flow_keys(keys, BPF_DROP);
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/* hlen is in 8-octets and does not include the first 8 bytes
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* of the header
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*/
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keys->thoff += (1 + ip6h->hdrlen) << 3;
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keys->ip_proto = ip6h->nexthdr;
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return parse_ipv6_proto(skb, ip6h->nexthdr);
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}
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PROG(IPV6FR)(struct __sk_buff *skb)
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{
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struct bpf_flow_keys *keys = skb->flow_keys;
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struct frag_hdr *fragh, _fragh;
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fragh = bpf_flow_dissect_get_header(skb, sizeof(*fragh), &_fragh);
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if (!fragh)
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return export_flow_keys(keys, BPF_DROP);
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keys->thoff += sizeof(*fragh);
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keys->is_frag = true;
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keys->ip_proto = fragh->nexthdr;
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if (!(fragh->frag_off & bpf_htons(IP6_OFFSET))) {
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keys->is_first_frag = true;
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/* No need to parse fragmented packet unless
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* explicitly asked for.
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*/
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if (!(keys->flags & BPF_FLOW_DISSECTOR_F_PARSE_1ST_FRAG))
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return export_flow_keys(keys, BPF_OK);
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} else {
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return export_flow_keys(keys, BPF_OK);
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}
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return parse_ipv6_proto(skb, fragh->nexthdr);
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}
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PROG(MPLS)(struct __sk_buff *skb)
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{
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struct bpf_flow_keys *keys = skb->flow_keys;
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struct mpls_label *mpls, _mpls;
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mpls = bpf_flow_dissect_get_header(skb, sizeof(*mpls), &_mpls);
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if (!mpls)
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return export_flow_keys(keys, BPF_DROP);
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return export_flow_keys(keys, BPF_OK);
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}
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PROG(VLAN)(struct __sk_buff *skb)
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{
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struct bpf_flow_keys *keys = skb->flow_keys;
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struct vlan_hdr *vlan, _vlan;
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/* Account for double-tagging */
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if (keys->n_proto == bpf_htons(ETH_P_8021AD)) {
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vlan = bpf_flow_dissect_get_header(skb, sizeof(*vlan), &_vlan);
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if (!vlan)
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return export_flow_keys(keys, BPF_DROP);
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if (vlan->h_vlan_encapsulated_proto != bpf_htons(ETH_P_8021Q))
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return export_flow_keys(keys, BPF_DROP);
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keys->nhoff += sizeof(*vlan);
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keys->thoff += sizeof(*vlan);
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}
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vlan = bpf_flow_dissect_get_header(skb, sizeof(*vlan), &_vlan);
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if (!vlan)
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return export_flow_keys(keys, BPF_DROP);
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keys->nhoff += sizeof(*vlan);
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keys->thoff += sizeof(*vlan);
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/* Only allow 8021AD + 8021Q double tagging and no triple tagging.*/
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if (vlan->h_vlan_encapsulated_proto == bpf_htons(ETH_P_8021AD) ||
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vlan->h_vlan_encapsulated_proto == bpf_htons(ETH_P_8021Q))
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return export_flow_keys(keys, BPF_DROP);
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keys->n_proto = vlan->h_vlan_encapsulated_proto;
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return parse_eth_proto(skb, vlan->h_vlan_encapsulated_proto);
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}
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char __license[] SEC("license") = "GPL";
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