// SPDX-License-Identifier: GPL-2.0
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/* Copyright (c) 2020 Facebook */
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#include <stddef.h>
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#include <errno.h>
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#include <stdbool.h>
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#include <sys/types.h>
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#include <sys/socket.h>
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#include <linux/ipv6.h>
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#include <linux/tcp.h>
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#include <linux/socket.h>
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#include <linux/bpf.h>
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#include <linux/types.h>
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#include <bpf/bpf_helpers.h>
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#include <bpf/bpf_endian.h>
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#define BPF_PROG_TEST_TCP_HDR_OPTIONS
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#include "test_tcp_hdr_options.h"
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__u16 last_addr16_n = __bpf_htons(1);
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__u16 active_lport_n = 0;
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__u16 active_lport_h = 0;
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__u16 passive_lport_n = 0;
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__u16 passive_lport_h = 0;
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/* options received at passive side */
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unsigned int nr_pure_ack = 0;
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unsigned int nr_data = 0;
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unsigned int nr_syn = 0;
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unsigned int nr_fin = 0;
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/* Check the header received from the active side */
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static int __check_active_hdr_in(struct bpf_sock_ops *skops, bool check_syn)
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{
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union {
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struct tcphdr th;
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struct ipv6hdr ip6;
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struct tcp_exprm_opt exprm_opt;
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struct tcp_opt reg_opt;
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__u8 data[100]; /* IPv6 (40) + Max TCP hdr (60) */
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} hdr = {};
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__u64 load_flags = check_syn ? BPF_LOAD_HDR_OPT_TCP_SYN : 0;
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struct tcphdr *pth;
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int ret;
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hdr.reg_opt.kind = 0xB9;
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/* The option is 4 bytes long instead of 2 bytes */
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ret = bpf_load_hdr_opt(skops, &hdr.reg_opt, 2, load_flags);
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if (ret != -ENOSPC)
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RET_CG_ERR(ret);
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/* Test searching magic with regular kind */
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hdr.reg_opt.len = 4;
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ret = bpf_load_hdr_opt(skops, &hdr.reg_opt, sizeof(hdr.reg_opt),
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load_flags);
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if (ret != -EINVAL)
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RET_CG_ERR(ret);
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hdr.reg_opt.len = 0;
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ret = bpf_load_hdr_opt(skops, &hdr.reg_opt, sizeof(hdr.reg_opt),
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load_flags);
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if (ret != 4 || hdr.reg_opt.len != 4 || hdr.reg_opt.kind != 0xB9 ||
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hdr.reg_opt.data[0] != 0xfa || hdr.reg_opt.data[1] != 0xce)
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RET_CG_ERR(ret);
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/* Test searching experimental option with invalid kind length */
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hdr.exprm_opt.kind = TCPOPT_EXP;
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hdr.exprm_opt.len = 5;
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hdr.exprm_opt.magic = 0;
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ret = bpf_load_hdr_opt(skops, &hdr.exprm_opt, sizeof(hdr.exprm_opt),
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load_flags);
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if (ret != -EINVAL)
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RET_CG_ERR(ret);
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/* Test searching experimental option with 0 magic value */
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hdr.exprm_opt.len = 4;
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ret = bpf_load_hdr_opt(skops, &hdr.exprm_opt, sizeof(hdr.exprm_opt),
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load_flags);
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if (ret != -ENOMSG)
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RET_CG_ERR(ret);
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hdr.exprm_opt.magic = __bpf_htons(0xeB9F);
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ret = bpf_load_hdr_opt(skops, &hdr.exprm_opt, sizeof(hdr.exprm_opt),
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load_flags);
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if (ret != 4 || hdr.exprm_opt.len != 4 ||
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hdr.exprm_opt.kind != TCPOPT_EXP ||
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hdr.exprm_opt.magic != __bpf_htons(0xeB9F))
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RET_CG_ERR(ret);
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if (!check_syn)
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return CG_OK;
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/* Test loading from skops->syn_skb if sk_state == TCP_NEW_SYN_RECV
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*
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* Test loading from tp->saved_syn for other sk_state.
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*/
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ret = bpf_getsockopt(skops, SOL_TCP, TCP_BPF_SYN_IP, &hdr.ip6,
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sizeof(hdr.ip6));
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if (ret != -ENOSPC)
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RET_CG_ERR(ret);
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if (hdr.ip6.saddr.s6_addr16[7] != last_addr16_n ||
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hdr.ip6.daddr.s6_addr16[7] != last_addr16_n)
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RET_CG_ERR(0);
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ret = bpf_getsockopt(skops, SOL_TCP, TCP_BPF_SYN_IP, &hdr, sizeof(hdr));
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if (ret < 0)
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RET_CG_ERR(ret);
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pth = (struct tcphdr *)(&hdr.ip6 + 1);
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if (pth->dest != passive_lport_n || pth->source != active_lport_n)
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RET_CG_ERR(0);
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ret = bpf_getsockopt(skops, SOL_TCP, TCP_BPF_SYN, &hdr, sizeof(hdr));
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if (ret < 0)
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RET_CG_ERR(ret);
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if (hdr.th.dest != passive_lport_n || hdr.th.source != active_lport_n)
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RET_CG_ERR(0);
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return CG_OK;
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}
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static int check_active_syn_in(struct bpf_sock_ops *skops)
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{
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return __check_active_hdr_in(skops, true);
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}
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static int check_active_hdr_in(struct bpf_sock_ops *skops)
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{
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struct tcphdr *th;
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if (__check_active_hdr_in(skops, false) == CG_ERR)
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return CG_ERR;
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th = skops->skb_data;
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if (th + 1 > skops->skb_data_end)
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RET_CG_ERR(0);
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if (tcp_hdrlen(th) < skops->skb_len)
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nr_data++;
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if (th->fin)
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nr_fin++;
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if (th->ack && !th->fin && tcp_hdrlen(th) == skops->skb_len)
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nr_pure_ack++;
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return CG_OK;
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}
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static int active_opt_len(struct bpf_sock_ops *skops)
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{
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int err;
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/* Reserve more than enough to allow the -EEXIST test in
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* the write_active_opt().
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*/
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err = bpf_reserve_hdr_opt(skops, 12, 0);
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if (err)
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RET_CG_ERR(err);
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return CG_OK;
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}
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static int write_active_opt(struct bpf_sock_ops *skops)
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{
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struct tcp_exprm_opt exprm_opt = {};
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struct tcp_opt win_scale_opt = {};
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struct tcp_opt reg_opt = {};
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struct tcphdr *th;
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int err, ret;
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exprm_opt.kind = TCPOPT_EXP;
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exprm_opt.len = 4;
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exprm_opt.magic = __bpf_htons(0xeB9F);
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reg_opt.kind = 0xB9;
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reg_opt.len = 4;
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reg_opt.data[0] = 0xfa;
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reg_opt.data[1] = 0xce;
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win_scale_opt.kind = TCPOPT_WINDOW;
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err = bpf_store_hdr_opt(skops, &exprm_opt, sizeof(exprm_opt), 0);
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if (err)
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RET_CG_ERR(err);
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/* Store the same exprm option */
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err = bpf_store_hdr_opt(skops, &exprm_opt, sizeof(exprm_opt), 0);
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if (err != -EEXIST)
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RET_CG_ERR(err);
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err = bpf_store_hdr_opt(skops, ®_opt, sizeof(reg_opt), 0);
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if (err)
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RET_CG_ERR(err);
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err = bpf_store_hdr_opt(skops, ®_opt, sizeof(reg_opt), 0);
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if (err != -EEXIST)
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RET_CG_ERR(err);
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/* Check the option has been written and can be searched */
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ret = bpf_load_hdr_opt(skops, &exprm_opt, sizeof(exprm_opt), 0);
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if (ret != 4 || exprm_opt.len != 4 || exprm_opt.kind != TCPOPT_EXP ||
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exprm_opt.magic != __bpf_htons(0xeB9F))
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RET_CG_ERR(ret);
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reg_opt.len = 0;
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ret = bpf_load_hdr_opt(skops, ®_opt, sizeof(reg_opt), 0);
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if (ret != 4 || reg_opt.len != 4 || reg_opt.kind != 0xB9 ||
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reg_opt.data[0] != 0xfa || reg_opt.data[1] != 0xce)
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RET_CG_ERR(ret);
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th = skops->skb_data;
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if (th + 1 > skops->skb_data_end)
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RET_CG_ERR(0);
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if (th->syn) {
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active_lport_h = skops->local_port;
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active_lport_n = th->source;
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/* Search the win scale option written by kernel
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* in the SYN packet.
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*/
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ret = bpf_load_hdr_opt(skops, &win_scale_opt,
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sizeof(win_scale_opt), 0);
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if (ret != 3 || win_scale_opt.len != 3 ||
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win_scale_opt.kind != TCPOPT_WINDOW)
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RET_CG_ERR(ret);
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/* Write the win scale option that kernel
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* has already written.
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*/
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err = bpf_store_hdr_opt(skops, &win_scale_opt,
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sizeof(win_scale_opt), 0);
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if (err != -EEXIST)
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RET_CG_ERR(err);
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}
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return CG_OK;
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}
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static int handle_hdr_opt_len(struct bpf_sock_ops *skops)
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{
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__u8 tcp_flags = skops_tcp_flags(skops);
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if ((tcp_flags & TCPHDR_SYNACK) == TCPHDR_SYNACK)
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/* Check the SYN from bpf_sock_ops_kern->syn_skb */
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return check_active_syn_in(skops);
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/* Passive side should have cleared the write hdr cb by now */
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if (skops->local_port == passive_lport_h)
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RET_CG_ERR(0);
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return active_opt_len(skops);
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}
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static int handle_write_hdr_opt(struct bpf_sock_ops *skops)
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{
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if (skops->local_port == passive_lport_h)
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RET_CG_ERR(0);
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return write_active_opt(skops);
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}
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static int handle_parse_hdr(struct bpf_sock_ops *skops)
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{
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/* Passive side is not writing any non-standard/unknown
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* option, so the active side should never be called.
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*/
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if (skops->local_port == active_lport_h)
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RET_CG_ERR(0);
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return check_active_hdr_in(skops);
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}
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static int handle_passive_estab(struct bpf_sock_ops *skops)
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{
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int err;
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/* No more write hdr cb */
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bpf_sock_ops_cb_flags_set(skops,
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skops->bpf_sock_ops_cb_flags &
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~BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG);
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/* Recheck the SYN but check the tp->saved_syn this time */
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err = check_active_syn_in(skops);
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if (err == CG_ERR)
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return err;
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nr_syn++;
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/* The ack has header option written by the active side also */
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return check_active_hdr_in(skops);
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}
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SEC("sockops/misc_estab")
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int misc_estab(struct bpf_sock_ops *skops)
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{
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int true_val = 1;
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switch (skops->op) {
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case BPF_SOCK_OPS_TCP_LISTEN_CB:
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passive_lport_h = skops->local_port;
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passive_lport_n = __bpf_htons(passive_lport_h);
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bpf_setsockopt(skops, SOL_TCP, TCP_SAVE_SYN,
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&true_val, sizeof(true_val));
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set_hdr_cb_flags(skops, 0);
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break;
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case BPF_SOCK_OPS_TCP_CONNECT_CB:
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set_hdr_cb_flags(skops, 0);
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break;
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case BPF_SOCK_OPS_PARSE_HDR_OPT_CB:
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return handle_parse_hdr(skops);
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case BPF_SOCK_OPS_HDR_OPT_LEN_CB:
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return handle_hdr_opt_len(skops);
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case BPF_SOCK_OPS_WRITE_HDR_OPT_CB:
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return handle_write_hdr_opt(skops);
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case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
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return handle_passive_estab(skops);
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}
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return CG_OK;
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}
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char _license[] SEC("license") = "GPL";
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