// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */
#include <linux/bpf.h>
#include <bpf/bpf_endian.h>
#include <bpf/bpf_helpers.h>
#include <linux/if_ether.h>
#include <linux/in.h>
#include <linux/in6.h>
#include <linux/ipv6.h>
#include <linux/tcp.h>
#include <sys/types.h>
#include <sys/socket.h>
#include "cgroup_tcp_skb.h"
char _license[] SEC("license") = "GPL";
__u16 g_sock_port = 0;
__u32 g_sock_state = 0;
int g_unexpected = 0;
__u32 g_packet_count = 0;
int needed_tcp_pkt(struct __sk_buff *skb, struct tcphdr *tcph)
{
struct ipv6hdr ip6h;
if (skb->protocol != bpf_htons(ETH_P_IPV6))
return 0;
if (bpf_skb_load_bytes(skb, 0, &ip6h, sizeof(ip6h)))
return 0;
if (ip6h.nexthdr != IPPROTO_TCP)
return 0;
if (bpf_skb_load_bytes(skb, sizeof(ip6h), tcph, sizeof(*tcph)))
return 0;
if (tcph->source != bpf_htons(g_sock_port) &&
tcph->dest != bpf_htons(g_sock_port))
return 0;
return 1;
}
/* Run accept() on a socket in the cgroup to receive a new connection. */
static int egress_accept(struct tcphdr *tcph)
{
if (g_sock_state == SYN_RECV_SENDING_SYN_ACK) {
if (tcph->fin || !tcph->syn || !tcph->ack)
g_unexpected++;
else
g_sock_state = SYN_RECV;
return 1;
}
return 0;
}
static int ingress_accept(struct tcphdr *tcph)
{
switch (g_sock_state) {
case INIT:
if (!tcph->syn || tcph->fin || tcph->ack)
g_unexpected++;
else
g_sock_state = SYN_RECV_SENDING_SYN_ACK;
break;
case SYN_RECV:
if (tcph->fin || tcph->syn || !tcph->ack)
g_unexpected++;
else
g_sock_state = ESTABLISHED;
break;
default:
return 0;
}
return 1;
}
/* Run connect() on a socket in the cgroup to start a new connection. */
static int egress_connect(struct tcphdr *tcph)
{
if (g_sock_state == INIT) {
if (!tcph->syn || tcph->fin || tcph->ack)
g_unexpected++;
else
g_sock_state = SYN_SENT;
return 1;
}
return 0;
}
static int ingress_connect(struct tcphdr *tcph)
{
if (g_sock_state == SYN_SENT) {
if (tcph->fin || !tcph->syn || !tcph->ack)
g_unexpected++;
else
g_sock_state = ESTABLISHED;
return 1;
}
return 0;
}
/* The connection is closed by the peer outside the cgroup. */
static int egress_close_remote(struct tcphdr *tcph)
{
switch (g_sock_state) {
case ESTABLISHED:
break;
case CLOSE_WAIT_SENDING_ACK:
if (tcph->fin || tcph->syn || !tcph->ack)
g_unexpected++;
else
g_sock_state = CLOSE_WAIT;
break;
case CLOSE_WAIT:
if (!tcph->fin)
g_unexpected++;
else
g_sock_state = LAST_ACK;
break;
default:
return 0;
}
return 1;
}
static int ingress_close_remote(struct tcphdr *tcph)
{
switch (g_sock_state) {
case ESTABLISHED:
if (tcph->fin)
g_sock_state = CLOSE_WAIT_SENDING_ACK;
break;
case LAST_ACK:
if (tcph->fin || tcph->syn || !tcph->ack)
g_unexpected++;
else
g_sock_state = CLOSED;
break;
default:
return 0;
}
return 1;
}
/* The connection is closed by the endpoint inside the cgroup. */
static int egress_close_local(struct tcphdr *tcph)
{
switch (g_sock_state) {
case ESTABLISHED:
if (tcph->fin)
g_sock_state = FIN_WAIT1;
break;
case TIME_WAIT_SENDING_ACK:
if (tcph->fin || tcph->syn || !tcph->ack)
g_unexpected++;
else
g_sock_state = TIME_WAIT;
break;
default:
return 0;
}
return 1;
}
static int ingress_close_local(struct tcphdr *tcph)
{
switch (g_sock_state) {
case ESTABLISHED:
break;
case FIN_WAIT1:
if (tcph->fin || tcph->syn || !tcph->ack)
g_unexpected++;
else
g_sock_state = FIN_WAIT2;
break;
case FIN_WAIT2:
if (!tcph->fin || tcph->syn || !tcph->ack)
g_unexpected++;
else
g_sock_state = TIME_WAIT_SENDING_ACK;
break;
default:
return 0;
}
return 1;
}
/* Check the types of outgoing packets of a server socket to make sure they
* are consistent with the state of the server socket.
*
* The connection is closed by the client side.
*/
SEC("cgroup_skb/egress")
int server_egress(struct __sk_buff *skb)
{
struct tcphdr tcph;
if (!needed_tcp_pkt(skb, &tcph))
return 1;
g_packet_count++;
/* Egress of the server socket. */
if (egress_accept(&tcph) || egress_close_remote(&tcph))
return 1;
g_unexpected++;
return 1;
}
/* Check the types of incoming packets of a server socket to make sure they
* are consistent with the state of the server socket.
*
* The connection is closed by the client side.
*/
SEC("cgroup_skb/ingress")
int server_ingress(struct __sk_buff *skb)
{
struct tcphdr tcph;
if (!needed_tcp_pkt(skb, &tcph))
return 1;
g_packet_count++;
/* Ingress of the server socket. */
if (ingress_accept(&tcph) || ingress_close_remote(&tcph))
return 1;
g_unexpected++;
return 1;
}
/* Check the types of outgoing packets of a server socket to make sure they
* are consistent with the state of the server socket.
*
* The connection is closed by the server side.
*/
SEC("cgroup_skb/egress")
int server_egress_srv(struct __sk_buff *skb)
{
struct tcphdr tcph;
if (!needed_tcp_pkt(skb, &tcph))
return 1;
g_packet_count++;
/* Egress of the server socket. */
if (egress_accept(&tcph) || egress_close_local(&tcph))
return 1;
g_unexpected++;
return 1;
}
/* Check the types of incoming packets of a server socket to make sure they
* are consistent with the state of the server socket.
*
* The connection is closed by the server side.
*/
SEC("cgroup_skb/ingress")
int server_ingress_srv(struct __sk_buff *skb)
{
struct tcphdr tcph;
if (!needed_tcp_pkt(skb, &tcph))
return 1;
g_packet_count++;
/* Ingress of the server socket. */
if (ingress_accept(&tcph) || ingress_close_local(&tcph))
return 1;
g_unexpected++;
return 1;
}
/* Check the types of outgoing packets of a client socket to make sure they
* are consistent with the state of the client socket.
*
* The connection is closed by the server side.
*/
SEC("cgroup_skb/egress")
int client_egress_srv(struct __sk_buff *skb)
{
struct tcphdr tcph;
if (!needed_tcp_pkt(skb, &tcph))
return 1;
g_packet_count++;
/* Egress of the server socket. */
if (egress_connect(&tcph) || egress_close_remote(&tcph))
return 1;
g_unexpected++;
return 1;
}
/* Check the types of incoming packets of a client socket to make sure they
* are consistent with the state of the client socket.
*
* The connection is closed by the server side.
*/
SEC("cgroup_skb/ingress")
int client_ingress_srv(struct __sk_buff *skb)
{
struct tcphdr tcph;
if (!needed_tcp_pkt(skb, &tcph))
return 1;
g_packet_count++;
/* Ingress of the server socket. */
if (ingress_connect(&tcph) || ingress_close_remote(&tcph))
return 1;
g_unexpected++;
return 1;
}
/* Check the types of outgoing packets of a client socket to make sure they
* are consistent with the state of the client socket.
*
* The connection is closed by the client side.
*/
SEC("cgroup_skb/egress")
int client_egress(struct __sk_buff *skb)
{
struct tcphdr tcph;
if (!needed_tcp_pkt(skb, &tcph))
return 1;
g_packet_count++;
/* Egress of the server socket. */
if (egress_connect(&tcph) || egress_close_local(&tcph))
return 1;
g_unexpected++;
return 1;
}
/* Check the types of incoming packets of a client socket to make sure they
* are consistent with the state of the client socket.
*
* The connection is closed by the client side.
*/
SEC("cgroup_skb/ingress")
int client_ingress(struct __sk_buff *skb)
{
struct tcphdr tcph;
if (!needed_tcp_pkt(skb, &tcph))
return 1;
g_packet_count++;
/* Ingress of the server socket. */
if (ingress_connect(&tcph) || ingress_close_local(&tcph))
return 1;
g_unexpected++;
return 1;
}
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