// 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/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"
#ifndef sizeof_field
#define sizeof_field(TYPE, MEMBER) sizeof((((TYPE *)0)->MEMBER))
#endif
__u8 test_kind = TCPOPT_EXP;
__u16 test_magic = 0xeB9F;
__u32 inherit_cb_flags = 0;
struct bpf_test_option passive_synack_out = {};
struct bpf_test_option passive_fin_out = {};
struct bpf_test_option passive_estab_in = {};
struct bpf_test_option passive_fin_in = {};
struct bpf_test_option active_syn_out = {};
struct bpf_test_option active_fin_out = {};
struct bpf_test_option active_estab_in = {};
struct bpf_test_option active_fin_in = {};
struct {
__uint(type, BPF_MAP_TYPE_SK_STORAGE);
__uint(map_flags, BPF_F_NO_PREALLOC);
__type(key, int);
__type(value, struct hdr_stg);
} hdr_stg_map SEC(".maps");
static bool skops_want_cookie(const struct bpf_sock_ops *skops)
{
return skops->args[0] == BPF_WRITE_HDR_TCP_SYNACK_COOKIE;
}
static bool skops_current_mss(const struct bpf_sock_ops *skops)
{
return skops->args[0] == BPF_WRITE_HDR_TCP_CURRENT_MSS;
}
static __u8 option_total_len(__u8 flags)
{
__u8 i, len = 1; /* +1 for flags */
if (!flags)
return 0;
/* RESEND bit does not use a byte */
for (i = OPTION_RESEND + 1; i < __NR_OPTION_FLAGS; i++)
len += !!TEST_OPTION_FLAGS(flags, i);
if (test_kind == TCPOPT_EXP)
return len + TCP_BPF_EXPOPT_BASE_LEN;
else
return len + 2; /* +1 kind, +1 kind-len */
}
static void write_test_option(const struct bpf_test_option *test_opt,
__u8 *data)
{
__u8 offset = 0;
data[offset++] = test_opt->flags;
if (TEST_OPTION_FLAGS(test_opt->flags, OPTION_MAX_DELACK_MS))
data[offset++] = test_opt->max_delack_ms;
if (TEST_OPTION_FLAGS(test_opt->flags, OPTION_RAND))
data[offset++] = test_opt->rand;
}
static int store_option(struct bpf_sock_ops *skops,
const struct bpf_test_option *test_opt)
{
union {
struct tcp_exprm_opt exprm;
struct tcp_opt regular;
} write_opt;
int err;
if (test_kind == TCPOPT_EXP) {
write_opt.exprm.kind = TCPOPT_EXP;
write_opt.exprm.len = option_total_len(test_opt->flags);
write_opt.exprm.magic = __bpf_htons(test_magic);
write_opt.exprm.data32 = 0;
write_test_option(test_opt, write_opt.exprm.data);
err = bpf_store_hdr_opt(skops, &write_opt.exprm,
sizeof(write_opt.exprm), 0);
} else {
write_opt.regular.kind = test_kind;
write_opt.regular.len = option_total_len(test_opt->flags);
write_opt.regular.data32 = 0;
write_test_option(test_opt, write_opt.regular.data);
err = bpf_store_hdr_opt(skops, &write_opt.regular,
sizeof(write_opt.regular), 0);
}
if (err)
RET_CG_ERR(err);
return CG_OK;
}
static int parse_test_option(struct bpf_test_option *opt, const __u8 *start)
{
opt->flags = *start++;
if (TEST_OPTION_FLAGS(opt->flags, OPTION_MAX_DELACK_MS))
opt->max_delack_ms = *start++;
if (TEST_OPTION_FLAGS(opt->flags, OPTION_RAND))
opt->rand = *start++;
return 0;
}
static int load_option(struct bpf_sock_ops *skops,
struct bpf_test_option *test_opt, bool from_syn)
{
union {
struct tcp_exprm_opt exprm;
struct tcp_opt regular;
} search_opt;
int ret, load_flags = from_syn ? BPF_LOAD_HDR_OPT_TCP_SYN : 0;
if (test_kind == TCPOPT_EXP) {
search_opt.exprm.kind = TCPOPT_EXP;
search_opt.exprm.len = 4;
search_opt.exprm.magic = __bpf_htons(test_magic);
search_opt.exprm.data32 = 0;
ret = bpf_load_hdr_opt(skops, &search_opt.exprm,
sizeof(search_opt.exprm), load_flags);
if (ret < 0)
return ret;
return parse_test_option(test_opt, search_opt.exprm.data);
} else {
search_opt.regular.kind = test_kind;
search_opt.regular.len = 0;
search_opt.regular.data32 = 0;
ret = bpf_load_hdr_opt(skops, &search_opt.regular,
sizeof(search_opt.regular), load_flags);
if (ret < 0)
return ret;
return parse_test_option(test_opt, search_opt.regular.data);
}
}
static int synack_opt_len(struct bpf_sock_ops *skops)
{
struct bpf_test_option test_opt = {};
__u8 optlen;
int err;
if (!passive_synack_out.flags)
return CG_OK;
err = load_option(skops, &test_opt, true);
/* bpf_test_option is not found */
if (err == -ENOMSG)
return CG_OK;
if (err)
RET_CG_ERR(err);
optlen = option_total_len(passive_synack_out.flags);
if (optlen) {
err = bpf_reserve_hdr_opt(skops, optlen, 0);
if (err)
RET_CG_ERR(err);
}
return CG_OK;
}
static int write_synack_opt(struct bpf_sock_ops *skops)
{
struct bpf_test_option opt;
if (!passive_synack_out.flags)
/* We should not even be called since no header
* space has been reserved.
*/
RET_CG_ERR(0);
opt = passive_synack_out;
if (skops_want_cookie(skops))
SET_OPTION_FLAGS(opt.flags, OPTION_RESEND);
return store_option(skops, &opt);
}
static int syn_opt_len(struct bpf_sock_ops *skops)
{
__u8 optlen;
int err;
if (!active_syn_out.flags)
return CG_OK;
optlen = option_total_len(active_syn_out.flags);
if (optlen) {
err = bpf_reserve_hdr_opt(skops, optlen, 0);
if (err)
RET_CG_ERR(err);
}
return CG_OK;
}
static int write_syn_opt(struct bpf_sock_ops *skops)
{
if (!active_syn_out.flags)
RET_CG_ERR(0);
return store_option(skops, &active_syn_out);
}
static int fin_opt_len(struct bpf_sock_ops *skops)
{
struct bpf_test_option *opt;
struct hdr_stg *hdr_stg;
__u8 optlen;
int err;
if (!skops->sk)
RET_CG_ERR(0);
hdr_stg = bpf_sk_storage_get(&hdr_stg_map, skops->sk, NULL, 0);
if (!hdr_stg)
RET_CG_ERR(0);
if (hdr_stg->active)
opt = &active_fin_out;
else
opt = &passive_fin_out;
optlen = option_total_len(opt->flags);
if (optlen) {
err = bpf_reserve_hdr_opt(skops, optlen, 0);
if (err)
RET_CG_ERR(err);
}
return CG_OK;
}
static int write_fin_opt(struct bpf_sock_ops *skops)
{
struct bpf_test_option *opt;
struct hdr_stg *hdr_stg;
if (!skops->sk)
RET_CG_ERR(0);
hdr_stg = bpf_sk_storage_get(&hdr_stg_map, skops->sk, NULL, 0);
if (!hdr_stg)
RET_CG_ERR(0);
if (hdr_stg->active)
opt = &active_fin_out;
else
opt = &passive_fin_out;
if (!opt->flags)
RET_CG_ERR(0);
return store_option(skops, opt);
}
static int resend_in_ack(struct bpf_sock_ops *skops)
{
struct hdr_stg *hdr_stg;
if (!skops->sk)
return -1;
hdr_stg = bpf_sk_storage_get(&hdr_stg_map, skops->sk, NULL, 0);
if (!hdr_stg)
return -1;
return !!hdr_stg->resend_syn;
}
static int nodata_opt_len(struct bpf_sock_ops *skops)
{
int resend;
resend = resend_in_ack(skops);
if (resend < 0)
RET_CG_ERR(0);
if (resend)
return syn_opt_len(skops);
return CG_OK;
}
static int write_nodata_opt(struct bpf_sock_ops *skops)
{
int resend;
resend = resend_in_ack(skops);
if (resend < 0)
RET_CG_ERR(0);
if (resend)
return write_syn_opt(skops);
return CG_OK;
}
static int data_opt_len(struct bpf_sock_ops *skops)
{
/* Same as the nodata version. Mostly to show
* an example usage on skops->skb_len.
*/
return nodata_opt_len(skops);
}
static int write_data_opt(struct bpf_sock_ops *skops)
{
return write_nodata_opt(skops);
}
static int current_mss_opt_len(struct bpf_sock_ops *skops)
{
/* Reserve maximum that may be needed */
int err;
err = bpf_reserve_hdr_opt(skops, option_total_len(OPTION_MASK), 0);
if (err)
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)
return synack_opt_len(skops);
if (tcp_flags & TCPHDR_SYN)
return syn_opt_len(skops);
if (tcp_flags & TCPHDR_FIN)
return fin_opt_len(skops);
if (skops_current_mss(skops))
/* The kernel is calculating the MSS */
return current_mss_opt_len(skops);
if (skops->skb_len)
return data_opt_len(skops);
return nodata_opt_len(skops);
}
static int handle_write_hdr_opt(struct bpf_sock_ops *skops)
{
__u8 tcp_flags = skops_tcp_flags(skops);
struct tcphdr *th;
if ((tcp_flags & TCPHDR_SYNACK) == TCPHDR_SYNACK)
return write_synack_opt(skops);
if (tcp_flags & TCPHDR_SYN)
return write_syn_opt(skops);
if (tcp_flags & TCPHDR_FIN)
return write_fin_opt(skops);
th = skops->skb_data;
if (th + 1 > skops->skb_data_end)
RET_CG_ERR(0);
if (skops->skb_len > tcp_hdrlen(th))
return write_data_opt(skops);
return write_nodata_opt(skops);
}
static int set_delack_max(struct bpf_sock_ops *skops, __u8 max_delack_ms)
{
__u32 max_delack_us = max_delack_ms * 1000;
return bpf_setsockopt(skops, SOL_TCP, TCP_BPF_DELACK_MAX,
&max_delack_us, sizeof(max_delack_us));
}
static int set_rto_min(struct bpf_sock_ops *skops, __u8 peer_max_delack_ms)
{
__u32 min_rto_us = peer_max_delack_ms * 1000;
return bpf_setsockopt(skops, SOL_TCP, TCP_BPF_RTO_MIN, &min_rto_us,
sizeof(min_rto_us));
}
static int handle_active_estab(struct bpf_sock_ops *skops)
{
struct hdr_stg init_stg = {
.active = true,
};
int err;
err = load_option(skops, &active_estab_in, false);
if (err && err != -ENOMSG)
RET_CG_ERR(err);
init_stg.resend_syn = TEST_OPTION_FLAGS(active_estab_in.flags,
OPTION_RESEND);
if (!skops->sk || !bpf_sk_storage_get(&hdr_stg_map, skops->sk,
&init_stg,
BPF_SK_STORAGE_GET_F_CREATE))
RET_CG_ERR(0);
if (init_stg.resend_syn)
/* Don't clear the write_hdr cb now because
* the ACK may get lost and retransmit may
* be needed.
*
* PARSE_ALL_HDR cb flag is set to learn if this
* resend_syn option has received by the peer.
*
* The header option will be resent until a valid
* packet is received at handle_parse_hdr()
* and all hdr cb flags will be cleared in
* handle_parse_hdr().
*/
set_parse_all_hdr_cb_flags(skops);
else if (!active_fin_out.flags)
/* No options will be written from now */
clear_hdr_cb_flags(skops);
if (active_syn_out.max_delack_ms) {
err = set_delack_max(skops, active_syn_out.max_delack_ms);
if (err)
RET_CG_ERR(err);
}
if (active_estab_in.max_delack_ms) {
err = set_rto_min(skops, active_estab_in.max_delack_ms);
if (err)
RET_CG_ERR(err);
}
return CG_OK;
}
static int handle_passive_estab(struct bpf_sock_ops *skops)
{
struct hdr_stg init_stg = {};
struct tcphdr *th;
int err;
inherit_cb_flags = skops->bpf_sock_ops_cb_flags;
err = load_option(skops, &passive_estab_in, true);
if (err == -ENOENT) {
/* saved_syn is not found. It was in syncookie mode.
* We have asked the active side to resend the options
* in ACK, so try to find the bpf_test_option from ACK now.
*/
err = load_option(skops, &passive_estab_in, false);
init_stg.syncookie = true;
}
/* ENOMSG: The bpf_test_option is not found which is fine.
* Bail out now for all other errors.
*/
if (err && err != -ENOMSG)
RET_CG_ERR(err);
th = skops->skb_data;
if (th + 1 > skops->skb_data_end)
RET_CG_ERR(0);
if (th->syn) {
/* Fastopen */
/* Cannot clear cb_flags to stop write_hdr cb.
* synack is not sent yet for fast open.
* Even it was, the synack may need to be retransmitted.
*
* PARSE_ALL_HDR cb flag is set to learn
* if synack has reached the peer.
* All cb_flags will be cleared in handle_parse_hdr().
*/
set_parse_all_hdr_cb_flags(skops);
init_stg.fastopen = true;
} else if (!passive_fin_out.flags) {
/* No options will be written from now */
clear_hdr_cb_flags(skops);
}
if (!skops->sk ||
!bpf_sk_storage_get(&hdr_stg_map, skops->sk, &init_stg,
BPF_SK_STORAGE_GET_F_CREATE))
RET_CG_ERR(0);
if (passive_synack_out.max_delack_ms) {
err = set_delack_max(skops, passive_synack_out.max_delack_ms);
if (err)
RET_CG_ERR(err);
}
if (passive_estab_in.max_delack_ms) {
err = set_rto_min(skops, passive_estab_in.max_delack_ms);
if (err)
RET_CG_ERR(err);
}
return CG_OK;
}
static int handle_parse_hdr(struct bpf_sock_ops *skops)
{
struct hdr_stg *hdr_stg;
struct tcphdr *th;
if (!skops->sk)
RET_CG_ERR(0);
th = skops->skb_data;
if (th + 1 > skops->skb_data_end)
RET_CG_ERR(0);
hdr_stg = bpf_sk_storage_get(&hdr_stg_map, skops->sk, NULL, 0);
if (!hdr_stg)
RET_CG_ERR(0);
if (hdr_stg->resend_syn || hdr_stg->fastopen)
/* The PARSE_ALL_HDR cb flag was turned on
* to ensure that the previously written
* options have reached the peer.
* Those previously written option includes:
* - Active side: resend_syn in ACK during syncookie
* or
* - Passive side: SYNACK during fastopen
*
* A valid packet has been received here after
* the 3WHS, so the PARSE_ALL_HDR cb flag
* can be cleared now.
*/
clear_parse_all_hdr_cb_flags(skops);
if (hdr_stg->resend_syn && !active_fin_out.flags)
/* Active side resent the syn option in ACK
* because the server was in syncookie mode.
* A valid packet has been received, so
* clear header cb flags if there is no
* more option to send.
*/
clear_hdr_cb_flags(skops);
if (hdr_stg->fastopen && !passive_fin_out.flags)
/* Passive side was in fastopen.
* A valid packet has been received, so
* the SYNACK has reached the peer.
* Clear header cb flags if there is no more
* option to send.
*/
clear_hdr_cb_flags(skops);
if (th->fin) {
struct bpf_test_option *fin_opt;
int err;
if (hdr_stg->active)
fin_opt = &active_fin_in;
else
fin_opt = &passive_fin_in;
err = load_option(skops, fin_opt, false);
if (err && err != -ENOMSG)
RET_CG_ERR(err);
}
return CG_OK;
}
SEC("sockops")
int estab(struct bpf_sock_ops *skops)
{
int true_val = 1;
switch (skops->op) {
case BPF_SOCK_OPS_TCP_LISTEN_CB:
bpf_setsockopt(skops, SOL_TCP, TCP_SAVE_SYN,
&true_val, sizeof(true_val));
set_hdr_cb_flags(skops, BPF_SOCK_OPS_STATE_CB_FLAG);
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);
case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:
return handle_active_estab(skops);
}
return CG_OK;
}
char _license[] SEC("license") = "GPL";
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