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1// SPDX-License-Identifier: GPL-2.02 3/* This parsing logic is taken from the open source library katran, a layer 44 * load balancer.5 *6 * This code logic using dynptrs can be found in test_parse_tcp_hdr_opt_dynptr.c7 *8 * https://github.com/facebookincubator/katran/blob/main/katran/lib/bpf/pckt_parsing.h9 */10 11#include <linux/bpf.h>12#include <bpf/bpf_helpers.h>13#include <linux/tcp.h>14#include <stdbool.h>15#include <linux/ipv6.h>16#include <linux/if_ether.h>17#include "test_tcp_hdr_options.h"18 19char _license[] SEC("license") = "GPL";20 21/* Kind number used for experiments */22const __u32 tcp_hdr_opt_kind_tpr = 0xFD;23/* Length of the tcp header option */24const __u32 tcp_hdr_opt_len_tpr = 6;25/* maximum number of header options to check to lookup server_id */26const __u32 tcp_hdr_opt_max_opt_checks = 15;27 28__u32 server_id;29 30struct hdr_opt_state {31 __u32 server_id;32 __u8 byte_offset;33 __u8 hdr_bytes_remaining;34};35 36static int parse_hdr_opt(const struct xdp_md *xdp, struct hdr_opt_state *state)37{38 const void *data = (void *)(long)xdp->data;39 const void *data_end = (void *)(long)xdp->data_end;40 __u8 *tcp_opt, kind, hdr_len;41 42 tcp_opt = (__u8 *)(data + state->byte_offset);43 if (tcp_opt + 1 > data_end)44 return -1;45 46 kind = tcp_opt[0];47 48 if (kind == TCPOPT_EOL)49 return -1;50 51 if (kind == TCPOPT_NOP) {52 state->hdr_bytes_remaining--;53 state->byte_offset++;54 return 0;55 }56 57 if (state->hdr_bytes_remaining < 2 ||58 tcp_opt + sizeof(__u8) + sizeof(__u8) > data_end)59 return -1;60 61 hdr_len = tcp_opt[1];62 if (hdr_len > state->hdr_bytes_remaining)63 return -1;64 65 if (kind == tcp_hdr_opt_kind_tpr) {66 if (hdr_len != tcp_hdr_opt_len_tpr)67 return -1;68 69 if (tcp_opt + tcp_hdr_opt_len_tpr > data_end)70 return -1;71 72 state->server_id = *(__u32 *)&tcp_opt[2];73 return 1;74 }75 76 state->hdr_bytes_remaining -= hdr_len;77 state->byte_offset += hdr_len;78 return 0;79}80 81SEC("xdp")82int xdp_ingress_v6(struct xdp_md *xdp)83{84 const void *data = (void *)(long)xdp->data;85 const void *data_end = (void *)(long)xdp->data_end;86 struct hdr_opt_state opt_state = {};87 __u8 tcp_hdr_opt_len = 0;88 struct tcphdr *tcp_hdr;89 __u64 tcp_offset = 0;90 int err;91 92 tcp_offset = sizeof(struct ethhdr) + sizeof(struct ipv6hdr);93 tcp_hdr = (struct tcphdr *)(data + tcp_offset);94 if (tcp_hdr + 1 > data_end)95 return XDP_DROP;96 97 tcp_hdr_opt_len = (tcp_hdr->doff * 4) - sizeof(struct tcphdr);98 if (tcp_hdr_opt_len < tcp_hdr_opt_len_tpr)99 return XDP_DROP;100 101 opt_state.hdr_bytes_remaining = tcp_hdr_opt_len;102 opt_state.byte_offset = sizeof(struct tcphdr) + tcp_offset;103 104 /* max number of bytes of options in tcp header is 40 bytes */105 for (int i = 0; i < tcp_hdr_opt_max_opt_checks; i++) {106 err = parse_hdr_opt(xdp, &opt_state);107 108 if (err || !opt_state.hdr_bytes_remaining)109 break;110 }111 112 if (!opt_state.server_id)113 return XDP_DROP;114 115 server_id = opt_state.server_id;116 117 return XDP_PASS;118}119