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nghttp2/bpf/reuseport_kern.c

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/*
* nghttp2 - HTTP/2 C Library
*
* Copyright (c) 2021 Tatsuhiro Tsujikawa
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
#include <stdlib.h>
#include <string.h>
#include <linux/in.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <linux/bpf.h>
#include <linux/types.h>
#include <linux/if_ether.h>
#include <bpf/bpf_endian.h>
#include <bpf/bpf_helpers.h>
/*
* How to compile:
*
* clang-12 -O2 -Wall -target bpf -g -c reuseport_kern.c -o reuseport_kern.o \
* -I/path/to/kernel/include
*
* See
* https://www.kernel.org/doc/Documentation/kbuild/headers_install.txt
* how to install kernel header files.
*/
/* rol32: From linux kernel source code */
/**
* rol32 - rotate a 32-bit value left
* @word: value to rotate
* @shift: bits to roll
*/
static inline __u32 rol32(__u32 word, unsigned int shift) {
return (word << shift) | (word >> ((-shift) & 31));
}
/* jhash.h: Jenkins hash support.
*
* Copyright (C) 2006. Bob Jenkins (bob_jenkins@burtleburtle.net)
*
* https://burtleburtle.net/bob/hash/
*
* These are the credits from Bob's sources:
*
* lookup3.c, by Bob Jenkins, May 2006, Public Domain.
*
* These are functions for producing 32-bit hashes for hash table lookup.
* hashword(), hashlittle(), hashlittle2(), hashbig(), mix(), and final()
* are externally useful functions. Routines to test the hash are included
* if SELF_TEST is defined. You can use this free for any purpose. It's in
* the public domain. It has no warranty.
*
* Copyright (C) 2009-2010 Jozsef Kadlecsik (kadlec@blackhole.kfki.hu)
*
* I've modified Bob's hash to be useful in the Linux kernel, and
* any bugs present are my fault.
* Jozsef
*/
/* __jhash_final - final mixing of 3 32-bit values (a,b,c) into c */
#define __jhash_final(a, b, c) \
{ \
c ^= b; \
c -= rol32(b, 14); \
a ^= c; \
a -= rol32(c, 11); \
b ^= a; \
b -= rol32(a, 25); \
c ^= b; \
c -= rol32(b, 16); \
a ^= c; \
a -= rol32(c, 4); \
b ^= a; \
b -= rol32(a, 14); \
c ^= b; \
c -= rol32(b, 24); \
}
/* __jhash_nwords - hash exactly 3, 2 or 1 word(s) */
static inline __u32 __jhash_nwords(__u32 a, __u32 b, __u32 c, __u32 initval) {
a += initval;
b += initval;
c += initval;
__jhash_final(a, b, c);
return c;
}
/* An arbitrary initial parameter */
#define JHASH_INITVAL 0xdeadbeef
static inline __u32 jhash_2words(__u32 a, __u32 b, __u32 initval) {
return __jhash_nwords(a, b, 0, initval + JHASH_INITVAL + (2 << 2));
}
struct bpf_map_def SEC("maps") cid_prefix_map = {
.type = BPF_MAP_TYPE_HASH,
.max_entries = 255,
.key_size = sizeof(__u64),
.value_size = sizeof(__u32),
};
struct bpf_map_def SEC("maps") reuseport_array = {
.type = BPF_MAP_TYPE_REUSEPORT_SOCKARRAY,
.max_entries = 255,
.key_size = sizeof(__u32),
.value_size = sizeof(__u32),
};
struct bpf_map_def SEC("maps") sk_info = {
.type = BPF_MAP_TYPE_ARRAY,
.max_entries = 1,
.key_size = sizeof(__u32),
.value_size = sizeof(__u32),
};
typedef struct quic_hd {
__u8 *dcid;
__u32 dcidlen;
__u32 dcid_offset;
__u8 type;
} quic_hd;
#define SV_DCIDLEN 20
#define MAX_DCIDLEN 20
#define MIN_DCIDLEN 8
#define CID_PREFIXLEN 8
enum {
NGTCP2_PKT_INITIAL = 0x0,
NGTCP2_PKT_0RTT = 0x1,
NGTCP2_PKT_HANDSHAKE = 0x2,
NGTCP2_PKT_SHORT = 0x40,
};
static inline int parse_quic(quic_hd *qhd, struct sk_reuseport_md *reuse_md) {
__u64 len = sizeof(struct udphdr) + 1;
__u8 *p;
__u64 dcidlen;
if (reuse_md->data + len > reuse_md->data_end) {
return -1;
}
p = reuse_md->data + sizeof(struct udphdr);
if (*p & 0x80) {
len += 4 + 1;
if (reuse_md->data + len > reuse_md->data_end) {
return -1;
}
p += 1 + 4;
dcidlen = *p;
if (dcidlen > MAX_DCIDLEN || dcidlen < MIN_DCIDLEN) {
return -1;
}
len += 1 + dcidlen;
if (reuse_md->data + len > reuse_md->data_end) {
return -1;
}
++p;
qhd->type =
(*((__u8 *)(reuse_md->data) + sizeof(struct udphdr)) & 0x30) >> 4;
qhd->dcid = p;
qhd->dcidlen = dcidlen;
qhd->dcid_offset = sizeof(struct udphdr) + 6;
} else {
len += SV_DCIDLEN;
if (reuse_md->data + len > reuse_md->data_end) {
return -1;
}
qhd->type = NGTCP2_PKT_SHORT;
qhd->dcid = (__u8 *)reuse_md->data + sizeof(struct udphdr) + 1;
qhd->dcidlen = SV_DCIDLEN;
qhd->dcid_offset = sizeof(struct udphdr) + 1;
}
return 0;
}
SEC("sk_reuseport")
int select_reuseport(struct sk_reuseport_md *reuse_md) {
__u32 sk_index, *psk_index;
__u8 sk_prefix[8];
__u32 *pnum_socks;
__u32 zero = 0;
int rv;
quic_hd qhd;
__u32 a, b;
rv = parse_quic(&qhd, reuse_md);
if (rv != 0) {
return SK_DROP;
}
switch (qhd.type) {
case NGTCP2_PKT_INITIAL:
case NGTCP2_PKT_0RTT:
if (reuse_md->data + qhd.dcid_offset + CID_PREFIXLEN > reuse_md->data_end) {
return SK_DROP;
}
memcpy(sk_prefix, reuse_md->data + sizeof(struct udphdr) + 6,
CID_PREFIXLEN);
if (qhd.dcidlen == SV_DCIDLEN) {
psk_index = bpf_map_lookup_elem(&cid_prefix_map, sk_prefix);
if (psk_index != NULL) {
sk_index = *psk_index;
break;
}
}
pnum_socks = bpf_map_lookup_elem(&sk_info, &zero);
if (pnum_socks == NULL) {
return SK_DROP;
}
a = (sk_prefix[0] << 24) | (sk_prefix[1] << 16) | (sk_prefix[2] << 8) |
sk_prefix[3];
b = (sk_prefix[4] << 24) | (sk_prefix[5] << 16) | (sk_prefix[6] << 8) |
sk_prefix[7];
sk_index = jhash_2words(a, b, reuse_md->hash) % *pnum_socks;
break;
case NGTCP2_PKT_HANDSHAKE:
case NGTCP2_PKT_SHORT:
if (qhd.dcidlen != SV_DCIDLEN) {
return SK_DROP;
}
if (reuse_md->data + qhd.dcid_offset + SV_DCIDLEN > reuse_md->data_end) {
return SK_DROP;
}
memcpy(sk_prefix, reuse_md->data + qhd.dcid_offset, CID_PREFIXLEN);
psk_index = bpf_map_lookup_elem(&cid_prefix_map, sk_prefix);
if (psk_index == NULL) {
pnum_socks = bpf_map_lookup_elem(&sk_info, &zero);
if (pnum_socks == NULL) {
return SK_DROP;
}
a = (sk_prefix[0] << 24) | (sk_prefix[1] << 16) | (sk_prefix[2] << 8) |
sk_prefix[3];
b = (sk_prefix[4] << 24) | (sk_prefix[5] << 16) | (sk_prefix[6] << 8) |
sk_prefix[7];
sk_index = jhash_2words(a, b, reuse_md->hash) % *pnum_socks;
break;
}
sk_index = *psk_index;
break;
default:
return SK_DROP;
}
rv = bpf_sk_select_reuseport(reuse_md, &reuseport_array, &sk_index, 0);
if (rv != 0) {
return SK_DROP;
}
return SK_PASS;
}
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