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