// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
// Copyright (c) 2019, 2020 Cloudflare
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <string.h>
#include <linux/bpf.h>
#include <linux/icmp.h>
#include <linux/icmpv6.h>
#include <linux/if_ether.h>
#include <linux/in.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/pkt_cls.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_endian.h>
#include "test_cls_redirect.h"
#ifdef SUBPROGS
#define INLINING __noinline
#else
#define INLINING __always_inline
#endif
#define offsetofend(TYPE, MEMBER) \
(offsetof(TYPE, MEMBER) + sizeof((((TYPE *)0)->MEMBER)))
#define IP_OFFSET_MASK (0x1FFF)
#define IP_MF (0x2000)
char _license[] SEC("license") = "Dual BSD/GPL";
/**
* Destination port and IP used for UDP encapsulation.
*/
volatile const __be16 ENCAPSULATION_PORT;
volatile const __be32 ENCAPSULATION_IP;
typedef struct {
uint64_t processed_packets_total;
uint64_t l3_protocol_packets_total_ipv4;
uint64_t l3_protocol_packets_total_ipv6;
uint64_t l4_protocol_packets_total_tcp;
uint64_t l4_protocol_packets_total_udp;
uint64_t accepted_packets_total_syn;
uint64_t accepted_packets_total_syn_cookies;
uint64_t accepted_packets_total_last_hop;
uint64_t accepted_packets_total_icmp_echo_request;
uint64_t accepted_packets_total_established;
uint64_t forwarded_packets_total_gue;
uint64_t forwarded_packets_total_gre;
uint64_t errors_total_unknown_l3_proto;
uint64_t errors_total_unknown_l4_proto;
uint64_t errors_total_malformed_ip;
uint64_t errors_total_fragmented_ip;
uint64_t errors_total_malformed_icmp;
uint64_t errors_total_unwanted_icmp;
uint64_t errors_total_malformed_icmp_pkt_too_big;
uint64_t errors_total_malformed_tcp;
uint64_t errors_total_malformed_udp;
uint64_t errors_total_icmp_echo_replies;
uint64_t errors_total_malformed_encapsulation;
uint64_t errors_total_encap_adjust_failed;
uint64_t errors_total_encap_buffer_too_small;
uint64_t errors_total_redirect_loop;
uint64_t errors_total_encap_mtu_violate;
} metrics_t;
typedef enum {
INVALID = 0,
UNKNOWN,
ECHO_REQUEST,
SYN,
SYN_COOKIE,
ESTABLISHED,
} verdict_t;
typedef struct {
uint16_t src, dst;
} flow_ports_t;
_Static_assert(
sizeof(flow_ports_t) !=
offsetofend(struct bpf_sock_tuple, ipv4.dport) -
offsetof(struct bpf_sock_tuple, ipv4.sport) - 1,
"flow_ports_t must match sport and dport in struct bpf_sock_tuple");
_Static_assert(
sizeof(flow_ports_t) !=
offsetofend(struct bpf_sock_tuple, ipv6.dport) -
offsetof(struct bpf_sock_tuple, ipv6.sport) - 1,
"flow_ports_t must match sport and dport in struct bpf_sock_tuple");
typedef int ret_t;
/* This is a bit of a hack. We need a return value which allows us to
* indicate that the regular flow of the program should continue,
* while allowing functions to use XDP_PASS and XDP_DROP, etc.
*/
static const ret_t CONTINUE_PROCESSING = -1;
/* Convenience macro to call functions which return ret_t.
*/
#define MAYBE_RETURN(x) \
do { \
ret_t __ret = x; \
if (__ret != CONTINUE_PROCESSING) \
return __ret; \
} while (0)
/* Linux packet pointers are either aligned to NET_IP_ALIGN (aka 2 bytes),
* or not aligned if the arch supports efficient unaligned access.
*
* Since the verifier ensures that eBPF packet accesses follow these rules,
* we can tell LLVM to emit code as if we always had a larger alignment.
* It will yell at us if we end up on a platform where this is not valid.
*/
typedef uint8_t *net_ptr __attribute__((align_value(8)));
typedef struct buf {
struct __sk_buff *skb;
net_ptr head;
/* NB: tail musn't have alignment other than 1, otherwise
* LLVM will go and eliminate code, e.g. when checking packet lengths.
*/
uint8_t *const tail;
} buf_t;
static __always_inline size_t buf_off(const buf_t *buf)
{
/* Clang seems to optimize constructs like
* a - b + c
* if c is known:
* r? = c
* r? -= b
* r? += a
*
* This is a problem if a and b are packet pointers,
* since the verifier allows subtracting two pointers to
* get a scalar, but not a scalar and a pointer.
*
* Use inline asm to break this optimization.
*/
size_t off = (size_t)buf->head;
asm("%0 -= %1" : "+r"(off) : "r"(buf->skb->data));
return off;
}
static __always_inline bool buf_copy(buf_t *buf, void *dst, size_t len)
{
if (bpf_skb_load_bytes(buf->skb, buf_off(buf), dst, len)) {
return false;
}
buf->head += len;
return true;
}
static __always_inline bool buf_skip(buf_t *buf, const size_t len)
{
/* Check whether off + len is valid in the non-linear part. */
if (buf_off(buf) + len > buf->skb->len) {
return false;
}
buf->head += len;
return true;
}
/* Returns a pointer to the start of buf, or NULL if len is
* larger than the remaining data. Consumes len bytes on a successful
* call.
*
* If scratch is not NULL, the function will attempt to load non-linear
* data via bpf_skb_load_bytes. On success, scratch is returned.
*/
static __always_inline void *buf_assign(buf_t *buf, const size_t len, void *scratch)
{
if (buf->head + len > buf->tail) {
if (scratch == NULL) {
return NULL;
}
return buf_copy(buf, scratch, len) ? scratch : NULL;
}
void *ptr = buf->head;
buf->head += len;
return ptr;
}
static INLINING bool pkt_skip_ipv4_options(buf_t *buf, const struct iphdr *ipv4)
{
if (ipv4->ihl <= 5) {
return true;
}
return buf_skip(buf, (ipv4->ihl - 5) * 4);
}
static INLINING bool ipv4_is_fragment(const struct iphdr *ip)
{
uint16_t frag_off = ip->frag_off & bpf_htons(IP_OFFSET_MASK);
return (ip->frag_off & bpf_htons(IP_MF)) != 0 || frag_off > 0;
}
static __always_inline struct iphdr *pkt_parse_ipv4(buf_t *pkt, struct iphdr *scratch)
{
struct iphdr *ipv4 = buf_assign(pkt, sizeof(*ipv4), scratch);
if (ipv4 == NULL) {
return NULL;
}
if (ipv4->ihl < 5) {
return NULL;
}
if (!pkt_skip_ipv4_options(pkt, ipv4)) {
return NULL;
}
return ipv4;
}
/* Parse the L4 ports from a packet, assuming a layout like TCP or UDP. */
static INLINING bool pkt_parse_icmp_l4_ports(buf_t *pkt, flow_ports_t *ports)
{
if (!buf_copy(pkt, ports, sizeof(*ports))) {
return false;
}
/* Ports in the L4 headers are reversed, since we are parsing an ICMP
* payload which is going towards the eyeball.
*/
uint16_t dst = ports->src;
ports->src = ports->dst;
ports->dst = dst;
return true;
}
static INLINING uint16_t pkt_checksum_fold(uint32_t csum)
{
/* The highest reasonable value for an IPv4 header
* checksum requires two folds, so we just do that always.
*/
csum = (csum & 0xffff) + (csum >> 16);
csum = (csum & 0xffff) + (csum >> 16);
return (uint16_t)~csum;
}
static INLINING void pkt_ipv4_checksum(struct iphdr *iph)
{
iph->check = 0;
/* An IP header without options is 20 bytes. Two of those
* are the checksum, which we always set to zero. Hence,
* the maximum accumulated value is 18 / 2 * 0xffff = 0x8fff7,
* which fits in 32 bit.
*/
_Static_assert(sizeof(struct iphdr) == 20, "iphdr must be 20 bytes");
uint32_t acc = 0;
uint16_t *ipw = (uint16_t *)iph;
#pragma clang loop unroll(full)
for (size_t i = 0; i < sizeof(struct iphdr) / 2; i++) {
acc += ipw[i];
}
iph->check = pkt_checksum_fold(acc);
}
static INLINING
bool pkt_skip_ipv6_extension_headers(buf_t *pkt,
const struct ipv6hdr *ipv6,
uint8_t *upper_proto,
bool *is_fragment)
{
/* We understand five extension headers.
* https://tools.ietf.org/html/rfc8200#section-4.1 states that all
* headers should occur once, except Destination Options, which may
* occur twice. Hence we give up after 6 headers.
*/
struct {
uint8_t next;
uint8_t len;
} exthdr = {
.next = ipv6->nexthdr,
};
*is_fragment = false;
#pragma clang loop unroll(full)
for (int i = 0; i < 6; i++) {
switch (exthdr.next) {
case IPPROTO_FRAGMENT:
*is_fragment = true;
/* NB: We don't check that hdrlen == 0 as per spec. */
/* fallthrough; */
case IPPROTO_HOPOPTS:
case IPPROTO_ROUTING:
case IPPROTO_DSTOPTS:
case IPPROTO_MH:
if (!buf_copy(pkt, &exthdr, sizeof(exthdr))) {
return false;
}
/* hdrlen is in 8-octet units, and excludes the first 8 octets. */
if (!buf_skip(pkt,
(exthdr.len + 1) * 8 - sizeof(exthdr))) {
return false;
}
/* Decode next header */
break;
default:
/* The next header is not one of the known extension
* headers, treat it as the upper layer header.
*
* This handles IPPROTO_NONE.
*
* Encapsulating Security Payload (50) and Authentication
* Header (51) also end up here (and will trigger an
* unknown proto error later). They have a custom header
* format and seem too esoteric to care about.
*/
*upper_proto = exthdr.next;
return true;
}
}
/* We never found an upper layer header. */
return false;
}
/* This function has to be inlined, because the verifier otherwise rejects it
* due to returning a pointer to the stack. This is technically correct, since
* scratch is allocated on the stack. However, this usage should be safe since
* it's the callers stack after all.
*/
static __always_inline struct ipv6hdr *
pkt_parse_ipv6(buf_t *pkt, struct ipv6hdr *scratch, uint8_t *proto,
bool *is_fragment)
{
struct ipv6hdr *ipv6 = buf_assign(pkt, sizeof(*ipv6), scratch);
if (ipv6 == NULL) {
return NULL;
}
if (!pkt_skip_ipv6_extension_headers(pkt, ipv6, proto, is_fragment)) {
return NULL;
}
return ipv6;
}
/* Global metrics, per CPU
*/
struct {
__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
__uint(max_entries, 1);
__type(key, unsigned int);
__type(value, metrics_t);
} metrics_map SEC(".maps");
static INLINING metrics_t *get_global_metrics(void)
{
uint64_t key = 0;
return bpf_map_lookup_elem(&metrics_map, &key);
}
static INLINING ret_t accept_locally(struct __sk_buff *skb, encap_headers_t *encap)
{
const int payload_off =
sizeof(*encap) +
sizeof(struct in_addr) * encap->unigue.hop_count;
int32_t encap_overhead = payload_off - sizeof(struct ethhdr);
// Changing the ethertype if the encapsulated packet is ipv6
if (encap->gue.proto_ctype == IPPROTO_IPV6) {
encap->eth.h_proto = bpf_htons(ETH_P_IPV6);
}
if (bpf_skb_adjust_room(skb, -encap_overhead, BPF_ADJ_ROOM_MAC,
BPF_F_ADJ_ROOM_FIXED_GSO |
BPF_F_ADJ_ROOM_NO_CSUM_RESET) ||
bpf_csum_level(skb, BPF_CSUM_LEVEL_DEC))
return TC_ACT_SHOT;
return bpf_redirect(skb->ifindex, BPF_F_INGRESS);
}
static INLINING ret_t forward_with_gre(struct __sk_buff *skb, encap_headers_t *encap,
struct in_addr *next_hop, metrics_t *metrics)
{
metrics->forwarded_packets_total_gre++;
const int payload_off =
sizeof(*encap) +
sizeof(struct in_addr) * encap->unigue.hop_count;
int32_t encap_overhead =
payload_off - sizeof(struct ethhdr) - sizeof(struct iphdr);
int32_t delta = sizeof(struct gre_base_hdr) - encap_overhead;
uint16_t proto = ETH_P_IP;
uint32_t mtu_len = 0;
/* Loop protection: the inner packet's TTL is decremented as a safeguard
* against any forwarding loop. As the only interesting field is the TTL
* hop limit for IPv6, it is easier to use bpf_skb_load_bytes/bpf_skb_store_bytes
* as they handle the split packets if needed (no need for the data to be
* in the linear section).
*/
if (encap->gue.proto_ctype == IPPROTO_IPV6) {
proto = ETH_P_IPV6;
uint8_t ttl;
int rc;
rc = bpf_skb_load_bytes(
skb, payload_off + offsetof(struct ipv6hdr, hop_limit),
&ttl, 1);
if (rc != 0) {
metrics->errors_total_malformed_encapsulation++;
return TC_ACT_SHOT;
}
if (ttl == 0) {
metrics->errors_total_redirect_loop++;
return TC_ACT_SHOT;
}
ttl--;
rc = bpf_skb_store_bytes(
skb, payload_off + offsetof(struct ipv6hdr, hop_limit),
&ttl, 1, 0);
if (rc != 0) {
metrics->errors_total_malformed_encapsulation++;
return TC_ACT_SHOT;
}
} else {
uint8_t ttl;
int rc;
rc = bpf_skb_load_bytes(
skb, payload_off + offsetof(struct iphdr, ttl), &ttl,
1);
if (rc != 0) {
metrics->errors_total_malformed_encapsulation++;
return TC_ACT_SHOT;
}
if (ttl == 0) {
metrics->errors_total_redirect_loop++;
return TC_ACT_SHOT;
}
/* IPv4 also has a checksum to patch. While the TTL is only one byte,
* this function only works for 2 and 4 bytes arguments (the result is
* the same).
*/
rc = bpf_l3_csum_replace(
skb, payload_off + offsetof(struct iphdr, check), ttl,
ttl - 1, 2);
if (rc != 0) {
metrics->errors_total_malformed_encapsulation++;
return TC_ACT_SHOT;
}
ttl--;
rc = bpf_skb_store_bytes(
skb, payload_off + offsetof(struct iphdr, ttl), &ttl, 1,
0);
if (rc != 0) {
metrics->errors_total_malformed_encapsulation++;
return TC_ACT_SHOT;
}
}
if (bpf_check_mtu(skb, skb->ifindex, &mtu_len, delta, 0)) {
metrics->errors_total_encap_mtu_violate++;
return TC_ACT_SHOT;
}
if (bpf_skb_adjust_room(skb, delta, BPF_ADJ_ROOM_NET,
BPF_F_ADJ_ROOM_FIXED_GSO |
BPF_F_ADJ_ROOM_NO_CSUM_RESET) ||
bpf_csum_level(skb, BPF_CSUM_LEVEL_INC)) {
metrics->errors_total_encap_adjust_failed++;
return TC_ACT_SHOT;
}
if (bpf_skb_pull_data(skb, sizeof(encap_gre_t))) {
metrics->errors_total_encap_buffer_too_small++;
return TC_ACT_SHOT;
}
buf_t pkt = {
.skb = skb,
.head = (uint8_t *)(long)skb->data,
.tail = (uint8_t *)(long)skb->data_end,
};
encap_gre_t *encap_gre = buf_assign(&pkt, sizeof(encap_gre_t), NULL);
if (encap_gre == NULL) {
metrics->errors_total_encap_buffer_too_small++;
return TC_ACT_SHOT;
}
encap_gre->ip.protocol = IPPROTO_GRE;
encap_gre->ip.daddr = next_hop->s_addr;
encap_gre->ip.saddr = ENCAPSULATION_IP;
encap_gre->ip.tot_len =
bpf_htons(bpf_ntohs(encap_gre->ip.tot_len) + delta);
encap_gre->gre.flags = 0;
encap_gre->gre.protocol = bpf_htons(proto);
pkt_ipv4_checksum((void *)&encap_gre->ip);
return bpf_redirect(skb->ifindex, 0);
}
static INLINING ret_t forward_to_next_hop(struct __sk_buff *skb, encap_headers_t *encap,
struct in_addr *next_hop, metrics_t *metrics)
{
/* swap L2 addresses */
/* This assumes that packets are received from a router.
* So just swapping the MAC addresses here will make the packet go back to
* the router, which will send it to the appropriate machine.
*/
unsigned char temp[ETH_ALEN];
memcpy(temp, encap->eth.h_dest, sizeof(temp));
memcpy(encap->eth.h_dest, encap->eth.h_source,
sizeof(encap->eth.h_dest));
memcpy(encap->eth.h_source, temp, sizeof(encap->eth.h_source));
if (encap->unigue.next_hop == encap->unigue.hop_count - 1 &&
encap->unigue.last_hop_gre) {
return forward_with_gre(skb, encap, next_hop, metrics);
}
metrics->forwarded_packets_total_gue++;
uint32_t old_saddr = encap->ip.saddr;
encap->ip.saddr = encap->ip.daddr;
encap->ip.daddr = next_hop->s_addr;
if (encap->unigue.next_hop < encap->unigue.hop_count) {
encap->unigue.next_hop++;
}
/* Remove ip->saddr, add next_hop->s_addr */
const uint64_t off = offsetof(typeof(*encap), ip.check);
int ret = bpf_l3_csum_replace(skb, off, old_saddr, next_hop->s_addr, 4);
if (ret < 0) {
return TC_ACT_SHOT;
}
return bpf_redirect(skb->ifindex, 0);
}
static INLINING ret_t skip_next_hops(buf_t *pkt, int n)
{
switch (n) {
case 1:
if (!buf_skip(pkt, sizeof(struct in_addr)))
return TC_ACT_SHOT;
case 0:
return CONTINUE_PROCESSING;
default:
return TC_ACT_SHOT;
}
}
/* Get the next hop from the GLB header.
*
* Sets next_hop->s_addr to 0 if there are no more hops left.
* pkt is positioned just after the variable length GLB header
* iff the call is successful.
*/
static INLINING ret_t get_next_hop(buf_t *pkt, encap_headers_t *encap,
struct in_addr *next_hop)
{
if (encap->unigue.next_hop > encap->unigue.hop_count) {
return TC_ACT_SHOT;
}
/* Skip "used" next hops. */
MAYBE_RETURN(skip_next_hops(pkt, encap->unigue.next_hop));
if (encap->unigue.next_hop == encap->unigue.hop_count) {
/* No more next hops, we are at the end of the GLB header. */
next_hop->s_addr = 0;
return CONTINUE_PROCESSING;
}
if (!buf_copy(pkt, next_hop, sizeof(*next_hop))) {
return TC_ACT_SHOT;
}
/* Skip the remaining next hops (may be zero). */
return skip_next_hops(pkt, encap->unigue.hop_count -
encap->unigue.next_hop - 1);
}
/* Fill a bpf_sock_tuple to be used with the socket lookup functions.
* This is a kludge that let's us work around verifier limitations:
*
* fill_tuple(&t, foo, sizeof(struct iphdr), 123, 321)
*
* clang will substitute a constant for sizeof, which allows the verifier
* to track its value. Based on this, it can figure out the constant
* return value, and calling code works while still being "generic" to
* IPv4 and IPv6.
*/
static INLINING uint64_t fill_tuple(struct bpf_sock_tuple *tuple, void *iph,
uint64_t iphlen, uint16_t sport, uint16_t dport)
{
switch (iphlen) {
case sizeof(struct iphdr): {
struct iphdr *ipv4 = (struct iphdr *)iph;
tuple->ipv4.daddr = ipv4->daddr;
tuple->ipv4.saddr = ipv4->saddr;
tuple->ipv4.sport = sport;
tuple->ipv4.dport = dport;
return sizeof(tuple->ipv4);
}
case sizeof(struct ipv6hdr): {
struct ipv6hdr *ipv6 = (struct ipv6hdr *)iph;
memcpy(&tuple->ipv6.daddr, &ipv6->daddr,
sizeof(tuple->ipv6.daddr));
memcpy(&tuple->ipv6.saddr, &ipv6->saddr,
sizeof(tuple->ipv6.saddr));
tuple->ipv6.sport = sport;
tuple->ipv6.dport = dport;
return sizeof(tuple->ipv6);
}
default:
return 0;
}
}
static INLINING verdict_t classify_tcp(struct __sk_buff *skb,
struct bpf_sock_tuple *tuple, uint64_t tuplen,
void *iph, struct tcphdr *tcp)
{
struct bpf_sock *sk =
bpf_skc_lookup_tcp(skb, tuple, tuplen, BPF_F_CURRENT_NETNS, 0);
if (sk == NULL) {
return UNKNOWN;
}
if (sk->state != BPF_TCP_LISTEN) {
bpf_sk_release(sk);
return ESTABLISHED;
}
if (iph != NULL && tcp != NULL) {
/* Kludge: we've run out of arguments, but need the length of the ip header. */
uint64_t iphlen = sizeof(struct iphdr);
if (tuplen == sizeof(tuple->ipv6)) {
iphlen = sizeof(struct ipv6hdr);
}
if (bpf_tcp_check_syncookie(sk, iph, iphlen, tcp,
sizeof(*tcp)) == 0) {
bpf_sk_release(sk);
return SYN_COOKIE;
}
}
bpf_sk_release(sk);
return UNKNOWN;
}
static INLINING verdict_t classify_udp(struct __sk_buff *skb,
struct bpf_sock_tuple *tuple, uint64_t tuplen)
{
struct bpf_sock *sk =
bpf_sk_lookup_udp(skb, tuple, tuplen, BPF_F_CURRENT_NETNS, 0);
if (sk == NULL) {
return UNKNOWN;
}
if (sk->state == BPF_TCP_ESTABLISHED) {
bpf_sk_release(sk);
return ESTABLISHED;
}
bpf_sk_release(sk);
return UNKNOWN;
}
static INLINING verdict_t classify_icmp(struct __sk_buff *skb, uint8_t proto,
struct bpf_sock_tuple *tuple, uint64_t tuplen,
metrics_t *metrics)
{
switch (proto) {
case IPPROTO_TCP:
return classify_tcp(skb, tuple, tuplen, NULL, NULL);
case IPPROTO_UDP:
return classify_udp(skb, tuple, tuplen);
default:
metrics->errors_total_malformed_icmp++;
return INVALID;
}
}
static INLINING verdict_t process_icmpv4(buf_t *pkt, metrics_t *metrics)
{
struct icmphdr icmp;
if (!buf_copy(pkt, &icmp, sizeof(icmp))) {
metrics->errors_total_malformed_icmp++;
return INVALID;
}
/* We should never receive encapsulated echo replies. */
if (icmp.type == ICMP_ECHOREPLY) {
metrics->errors_total_icmp_echo_replies++;
return INVALID;
}
if (icmp.type == ICMP_ECHO) {
return ECHO_REQUEST;
}
if (icmp.type != ICMP_DEST_UNREACH || icmp.code != ICMP_FRAG_NEEDED) {
metrics->errors_total_unwanted_icmp++;
return INVALID;
}
struct iphdr _ip4;
const struct iphdr *ipv4 = pkt_parse_ipv4(pkt, &_ip4);
if (ipv4 == NULL) {
metrics->errors_total_malformed_icmp_pkt_too_big++;
return INVALID;
}
/* The source address in the outer IP header is from the entity that
* originated the ICMP message. Use the original IP header to restore
* the correct flow tuple.
*/
struct bpf_sock_tuple tuple;
tuple.ipv4.saddr = ipv4->daddr;
tuple.ipv4.daddr = ipv4->saddr;
if (!pkt_parse_icmp_l4_ports(pkt, (flow_ports_t *)&tuple.ipv4.sport)) {
metrics->errors_total_malformed_icmp_pkt_too_big++;
return INVALID;
}
return classify_icmp(pkt->skb, ipv4->protocol, &tuple,
sizeof(tuple.ipv4), metrics);
}
static INLINING verdict_t process_icmpv6(buf_t *pkt, metrics_t *metrics)
{
struct icmp6hdr icmp6;
if (!buf_copy(pkt, &icmp6, sizeof(icmp6))) {
metrics->errors_total_malformed_icmp++;
return INVALID;
}
/* We should never receive encapsulated echo replies. */
if (icmp6.icmp6_type == ICMPV6_ECHO_REPLY) {
metrics->errors_total_icmp_echo_replies++;
return INVALID;
}
if (icmp6.icmp6_type == ICMPV6_ECHO_REQUEST) {
return ECHO_REQUEST;
}
if (icmp6.icmp6_type != ICMPV6_PKT_TOOBIG) {
metrics->errors_total_unwanted_icmp++;
return INVALID;
}
bool is_fragment;
uint8_t l4_proto;
struct ipv6hdr _ipv6;
const struct ipv6hdr *ipv6 =
pkt_parse_ipv6(pkt, &_ipv6, &l4_proto, &is_fragment);
if (ipv6 == NULL) {
metrics->errors_total_malformed_icmp_pkt_too_big++;
return INVALID;
}
if (is_fragment) {
metrics->errors_total_fragmented_ip++;
return INVALID;
}
/* Swap source and dest addresses. */
struct bpf_sock_tuple tuple;
memcpy(&tuple.ipv6.saddr, &ipv6->daddr, sizeof(tuple.ipv6.saddr));
memcpy(&tuple.ipv6.daddr, &ipv6->saddr, sizeof(tuple.ipv6.daddr));
if (!pkt_parse_icmp_l4_ports(pkt, (flow_ports_t *)&tuple.ipv6.sport)) {
metrics->errors_total_malformed_icmp_pkt_too_big++;
return INVALID;
}
return classify_icmp(pkt->skb, l4_proto, &tuple, sizeof(tuple.ipv6),
metrics);
}
static INLINING verdict_t process_tcp(buf_t *pkt, void *iph, uint64_t iphlen,
metrics_t *metrics)
{
metrics->l4_protocol_packets_total_tcp++;
struct tcphdr _tcp;
struct tcphdr *tcp = buf_assign(pkt, sizeof(_tcp), &_tcp);
if (tcp == NULL) {
metrics->errors_total_malformed_tcp++;
return INVALID;
}
if (tcp->syn) {
return SYN;
}
struct bpf_sock_tuple tuple;
uint64_t tuplen =
fill_tuple(&tuple, iph, iphlen, tcp->source, tcp->dest);
return classify_tcp(pkt->skb, &tuple, tuplen, iph, tcp);
}
static INLINING verdict_t process_udp(buf_t *pkt, void *iph, uint64_t iphlen,
metrics_t *metrics)
{
metrics->l4_protocol_packets_total_udp++;
struct udphdr _udp;
struct udphdr *udph = buf_assign(pkt, sizeof(_udp), &_udp);
if (udph == NULL) {
metrics->errors_total_malformed_udp++;
return INVALID;
}
struct bpf_sock_tuple tuple;
uint64_t tuplen =
fill_tuple(&tuple, iph, iphlen, udph->source, udph->dest);
return classify_udp(pkt->skb, &tuple, tuplen);
}
static INLINING verdict_t process_ipv4(buf_t *pkt, metrics_t *metrics)
{
metrics->l3_protocol_packets_total_ipv4++;
struct iphdr _ip4;
struct iphdr *ipv4 = pkt_parse_ipv4(pkt, &_ip4);
if (ipv4 == NULL) {
metrics->errors_total_malformed_ip++;
return INVALID;
}
if (ipv4->version != 4) {
metrics->errors_total_malformed_ip++;
return INVALID;
}
if (ipv4_is_fragment(ipv4)) {
metrics->errors_total_fragmented_ip++;
return INVALID;
}
switch (ipv4->protocol) {
case IPPROTO_ICMP:
return process_icmpv4(pkt, metrics);
case IPPROTO_TCP:
return process_tcp(pkt, ipv4, sizeof(*ipv4), metrics);
case IPPROTO_UDP:
return process_udp(pkt, ipv4, sizeof(*ipv4), metrics);
default:
metrics->errors_total_unknown_l4_proto++;
return INVALID;
}
}
static INLINING verdict_t process_ipv6(buf_t *pkt, metrics_t *metrics)
{
metrics->l3_protocol_packets_total_ipv6++;
uint8_t l4_proto;
bool is_fragment;
struct ipv6hdr _ipv6;
struct ipv6hdr *ipv6 =
pkt_parse_ipv6(pkt, &_ipv6, &l4_proto, &is_fragment);
if (ipv6 == NULL) {
metrics->errors_total_malformed_ip++;
return INVALID;
}
if (ipv6->version != 6) {
metrics->errors_total_malformed_ip++;
return INVALID;
}
if (is_fragment) {
metrics->errors_total_fragmented_ip++;
return INVALID;
}
switch (l4_proto) {
case IPPROTO_ICMPV6:
return process_icmpv6(pkt, metrics);
case IPPROTO_TCP:
return process_tcp(pkt, ipv6, sizeof(*ipv6), metrics);
case IPPROTO_UDP:
return process_udp(pkt, ipv6, sizeof(*ipv6), metrics);
default:
metrics->errors_total_unknown_l4_proto++;
return INVALID;
}
}
SEC("tc")
int cls_redirect(struct __sk_buff *skb)
{
metrics_t *metrics = get_global_metrics();
if (metrics == NULL) {
return TC_ACT_SHOT;
}
metrics->processed_packets_total++;
/* Pass bogus packets as long as we're not sure they're
* destined for us.
*/
if (skb->protocol != bpf_htons(ETH_P_IP)) {
return TC_ACT_OK;
}
encap_headers_t *encap;
/* Make sure that all encapsulation headers are available in
* the linear portion of the skb. This makes it easy to manipulate them.
*/
if (bpf_skb_pull_data(skb, sizeof(*encap))) {
return TC_ACT_OK;
}
buf_t pkt = {
.skb = skb,
.head = (uint8_t *)(long)skb->data,
.tail = (uint8_t *)(long)skb->data_end,
};
encap = buf_assign(&pkt, sizeof(*encap), NULL);
if (encap == NULL) {
return TC_ACT_OK;
}
if (encap->ip.ihl != 5) {
/* We never have any options. */
return TC_ACT_OK;
}
if (encap->ip.daddr != ENCAPSULATION_IP ||
encap->ip.protocol != IPPROTO_UDP) {
return TC_ACT_OK;
}
/* TODO Check UDP length? */
if (encap->udp.dest != ENCAPSULATION_PORT) {
return TC_ACT_OK;
}
/* We now know that the packet is destined to us, we can
* drop bogus ones.
*/
if (ipv4_is_fragment((void *)&encap->ip)) {
metrics->errors_total_fragmented_ip++;
return TC_ACT_SHOT;
}
if (encap->gue.variant != 0) {
metrics->errors_total_malformed_encapsulation++;
return TC_ACT_SHOT;
}
if (encap->gue.control != 0) {
metrics->errors_total_malformed_encapsulation++;
return TC_ACT_SHOT;
}
if (encap->gue.flags != 0) {
metrics->errors_total_malformed_encapsulation++;
return TC_ACT_SHOT;
}
if (encap->gue.hlen !=
sizeof(encap->unigue) / 4 + encap->unigue.hop_count) {
metrics->errors_total_malformed_encapsulation++;
return TC_ACT_SHOT;
}
if (encap->unigue.version != 0) {
metrics->errors_total_malformed_encapsulation++;
return TC_ACT_SHOT;
}
if (encap->unigue.reserved != 0) {
return TC_ACT_SHOT;
}
struct in_addr next_hop;
MAYBE_RETURN(get_next_hop(&pkt, encap, &next_hop));
if (next_hop.s_addr == 0) {
metrics->accepted_packets_total_last_hop++;
return accept_locally(skb, encap);
}
verdict_t verdict;
switch (encap->gue.proto_ctype) {
case IPPROTO_IPIP:
verdict = process_ipv4(&pkt, metrics);
break;
case IPPROTO_IPV6:
verdict = process_ipv6(&pkt, metrics);
break;
default:
metrics->errors_total_unknown_l3_proto++;
return TC_ACT_SHOT;
}
switch (verdict) {
case INVALID:
/* metrics have already been bumped */
return TC_ACT_SHOT;
case UNKNOWN:
return forward_to_next_hop(skb, encap, &next_hop, metrics);
case ECHO_REQUEST:
metrics->accepted_packets_total_icmp_echo_request++;
break;
case SYN:
if (encap->unigue.forward_syn) {
return forward_to_next_hop(skb, encap, &next_hop,
metrics);
}
metrics->accepted_packets_total_syn++;
break;
case SYN_COOKIE:
metrics->accepted_packets_total_syn_cookies++;
break;
case ESTABLISHED:
metrics->accepted_packets_total_established++;
break;
}
return accept_locally(skb, encap);
}