diff options
author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-06-19 21:00:30 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-06-19 21:00:30 +0000 |
commit | e54def4ad8144ab15f826416e2e0f290ef1901b4 (patch) | |
tree | 583f8d4bd95cd67c44ff37b878a7eddfca9ab97a /tools/testing/selftests/bpf/progs/test_tcp_custom_syncookie.c | |
parent | Adding upstream version 6.8.12. (diff) | |
download | linux-e54def4ad8144ab15f826416e2e0f290ef1901b4.tar.xz linux-e54def4ad8144ab15f826416e2e0f290ef1901b4.zip |
Adding upstream version 6.9.2.
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'tools/testing/selftests/bpf/progs/test_tcp_custom_syncookie.c')
-rw-r--r-- | tools/testing/selftests/bpf/progs/test_tcp_custom_syncookie.c | 595 |
1 files changed, 595 insertions, 0 deletions
diff --git a/tools/testing/selftests/bpf/progs/test_tcp_custom_syncookie.c b/tools/testing/selftests/bpf/progs/test_tcp_custom_syncookie.c new file mode 100644 index 0000000000..c8e4553648 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/test_tcp_custom_syncookie.c @@ -0,0 +1,595 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright Amazon.com Inc. or its affiliates. */ + +#include "vmlinux.h" + +#include <bpf/bpf_helpers.h> +#include <bpf/bpf_endian.h> +#include "bpf_tracing_net.h" +#include "bpf_kfuncs.h" +#include "test_siphash.h" +#include "test_tcp_custom_syncookie.h" + +#define MAX_PACKET_OFF 0xffff + +/* Hash is calculated for each client and split into ISN and TS. + * + * MSB LSB + * ISN: | 31 ... 8 | 7 6 | 5 | 4 | 3 2 1 0 | + * | Hash_1 | MSS | ECN | SACK | WScale | + * + * TS: | 31 ... 8 | 7 ... 0 | + * | Random | Hash_2 | + */ +#define COOKIE_BITS 8 +#define COOKIE_MASK (((__u32)1 << COOKIE_BITS) - 1) + +enum { + /* 0xf is invalid thus means that SYN did not have WScale. */ + BPF_SYNCOOKIE_WSCALE_MASK = (1 << 4) - 1, + BPF_SYNCOOKIE_SACK = (1 << 4), + BPF_SYNCOOKIE_ECN = (1 << 5), +}; + +#define MSS_LOCAL_IPV4 65495 +#define MSS_LOCAL_IPV6 65476 + +const __u16 msstab4[] = { + 536, + 1300, + 1460, + MSS_LOCAL_IPV4, +}; + +const __u16 msstab6[] = { + 1280 - 60, /* IPV6_MIN_MTU - 60 */ + 1480 - 60, + 9000 - 60, + MSS_LOCAL_IPV6, +}; + +static siphash_key_t test_key_siphash = { + { 0x0706050403020100ULL, 0x0f0e0d0c0b0a0908ULL } +}; + +struct tcp_syncookie { + struct __sk_buff *skb; + void *data; + void *data_end; + struct ethhdr *eth; + struct iphdr *ipv4; + struct ipv6hdr *ipv6; + struct tcphdr *tcp; + __be32 *ptr32; + struct bpf_tcp_req_attrs attrs; + u32 off; + u32 cookie; + u64 first; +}; + +bool handled_syn, handled_ack; + +static int tcp_load_headers(struct tcp_syncookie *ctx) +{ + ctx->data = (void *)(long)ctx->skb->data; + ctx->data_end = (void *)(long)ctx->skb->data_end; + ctx->eth = (struct ethhdr *)(long)ctx->skb->data; + + if (ctx->eth + 1 > ctx->data_end) + goto err; + + switch (bpf_ntohs(ctx->eth->h_proto)) { + case ETH_P_IP: + ctx->ipv4 = (struct iphdr *)(ctx->eth + 1); + + if (ctx->ipv4 + 1 > ctx->data_end) + goto err; + + if (ctx->ipv4->ihl != sizeof(*ctx->ipv4) / 4) + goto err; + + if (ctx->ipv4->version != 4) + goto err; + + if (ctx->ipv4->protocol != IPPROTO_TCP) + goto err; + + ctx->tcp = (struct tcphdr *)(ctx->ipv4 + 1); + break; + case ETH_P_IPV6: + ctx->ipv6 = (struct ipv6hdr *)(ctx->eth + 1); + + if (ctx->ipv6 + 1 > ctx->data_end) + goto err; + + if (ctx->ipv6->version != 6) + goto err; + + if (ctx->ipv6->nexthdr != NEXTHDR_TCP) + goto err; + + ctx->tcp = (struct tcphdr *)(ctx->ipv6 + 1); + break; + default: + goto err; + } + + if (ctx->tcp + 1 > ctx->data_end) + goto err; + + return 0; +err: + return -1; +} + +static int tcp_reload_headers(struct tcp_syncookie *ctx) +{ + /* Without volatile, + * R3 32-bit pointer arithmetic prohibited + */ + volatile u64 data_len = ctx->skb->data_end - ctx->skb->data; + + if (ctx->tcp->doff < sizeof(*ctx->tcp) / 4) + goto err; + + /* Needed to calculate csum and parse TCP options. */ + if (bpf_skb_change_tail(ctx->skb, data_len + 60 - ctx->tcp->doff * 4, 0)) + goto err; + + ctx->data = (void *)(long)ctx->skb->data; + ctx->data_end = (void *)(long)ctx->skb->data_end; + ctx->eth = (struct ethhdr *)(long)ctx->skb->data; + if (ctx->ipv4) { + ctx->ipv4 = (struct iphdr *)(ctx->eth + 1); + ctx->ipv6 = NULL; + ctx->tcp = (struct tcphdr *)(ctx->ipv4 + 1); + } else { + ctx->ipv4 = NULL; + ctx->ipv6 = (struct ipv6hdr *)(ctx->eth + 1); + ctx->tcp = (struct tcphdr *)(ctx->ipv6 + 1); + } + + if ((void *)ctx->tcp + 60 > ctx->data_end) + goto err; + + return 0; +err: + return -1; +} + +static __sum16 tcp_v4_csum(struct tcp_syncookie *ctx, __wsum csum) +{ + return csum_tcpudp_magic(ctx->ipv4->saddr, ctx->ipv4->daddr, + ctx->tcp->doff * 4, IPPROTO_TCP, csum); +} + +static __sum16 tcp_v6_csum(struct tcp_syncookie *ctx, __wsum csum) +{ + return csum_ipv6_magic(&ctx->ipv6->saddr, &ctx->ipv6->daddr, + ctx->tcp->doff * 4, IPPROTO_TCP, csum); +} + +static int tcp_validate_header(struct tcp_syncookie *ctx) +{ + s64 csum; + + if (tcp_reload_headers(ctx)) + goto err; + + csum = bpf_csum_diff(0, 0, (void *)ctx->tcp, ctx->tcp->doff * 4, 0); + if (csum < 0) + goto err; + + if (ctx->ipv4) { + /* check tcp_v4_csum(csum) is 0 if not on lo. */ + + csum = bpf_csum_diff(0, 0, (void *)ctx->ipv4, ctx->ipv4->ihl * 4, 0); + if (csum < 0) + goto err; + + if (csum_fold(csum) != 0) + goto err; + } else if (ctx->ipv6) { + /* check tcp_v6_csum(csum) is 0 if not on lo. */ + } + + return 0; +err: + return -1; +} + +static __always_inline void *next(struct tcp_syncookie *ctx, __u32 sz) +{ + __u64 off = ctx->off; + __u8 *data; + + /* Verifier forbids access to packet when offset exceeds MAX_PACKET_OFF */ + if (off > MAX_PACKET_OFF - sz) + return NULL; + + data = ctx->data + off; + barrier_var(data); + if (data + sz >= ctx->data_end) + return NULL; + + ctx->off += sz; + return data; +} + +static int tcp_parse_option(__u32 index, struct tcp_syncookie *ctx) +{ + __u8 *opcode, *opsize, *wscale; + __u32 *tsval, *tsecr; + __u16 *mss; + __u32 off; + + off = ctx->off; + opcode = next(ctx, 1); + if (!opcode) + goto stop; + + if (*opcode == TCPOPT_EOL) + goto stop; + + if (*opcode == TCPOPT_NOP) + goto next; + + opsize = next(ctx, 1); + if (!opsize) + goto stop; + + if (*opsize < 2) + goto stop; + + switch (*opcode) { + case TCPOPT_MSS: + mss = next(ctx, 2); + if (*opsize == TCPOLEN_MSS && ctx->tcp->syn && mss) + ctx->attrs.mss = get_unaligned_be16(mss); + break; + case TCPOPT_WINDOW: + wscale = next(ctx, 1); + if (*opsize == TCPOLEN_WINDOW && ctx->tcp->syn && wscale) { + ctx->attrs.wscale_ok = 1; + ctx->attrs.snd_wscale = *wscale; + } + break; + case TCPOPT_TIMESTAMP: + tsval = next(ctx, 4); + tsecr = next(ctx, 4); + if (*opsize == TCPOLEN_TIMESTAMP && tsval && tsecr) { + ctx->attrs.rcv_tsval = get_unaligned_be32(tsval); + ctx->attrs.rcv_tsecr = get_unaligned_be32(tsecr); + + if (ctx->tcp->syn && ctx->attrs.rcv_tsecr) + ctx->attrs.tstamp_ok = 0; + else + ctx->attrs.tstamp_ok = 1; + } + break; + case TCPOPT_SACK_PERM: + if (*opsize == TCPOLEN_SACK_PERM && ctx->tcp->syn) + ctx->attrs.sack_ok = 1; + break; + } + + ctx->off = off + *opsize; +next: + return 0; +stop: + return 1; +} + +static void tcp_parse_options(struct tcp_syncookie *ctx) +{ + ctx->off = (__u8 *)(ctx->tcp + 1) - (__u8 *)ctx->data, + + bpf_loop(40, tcp_parse_option, ctx, 0); +} + +static int tcp_validate_sysctl(struct tcp_syncookie *ctx) +{ + if ((ctx->ipv4 && ctx->attrs.mss != MSS_LOCAL_IPV4) || + (ctx->ipv6 && ctx->attrs.mss != MSS_LOCAL_IPV6)) + goto err; + + if (!ctx->attrs.wscale_ok || ctx->attrs.snd_wscale != 7) + goto err; + + if (!ctx->attrs.tstamp_ok) + goto err; + + if (!ctx->attrs.sack_ok) + goto err; + + if (!ctx->tcp->ece || !ctx->tcp->cwr) + goto err; + + return 0; +err: + return -1; +} + +static void tcp_prepare_cookie(struct tcp_syncookie *ctx) +{ + u32 seq = bpf_ntohl(ctx->tcp->seq); + u64 first = 0, second; + int mssind = 0; + u32 hash; + + if (ctx->ipv4) { + for (mssind = ARRAY_SIZE(msstab4) - 1; mssind; mssind--) + if (ctx->attrs.mss >= msstab4[mssind]) + break; + + ctx->attrs.mss = msstab4[mssind]; + + first = (u64)ctx->ipv4->saddr << 32 | ctx->ipv4->daddr; + } else if (ctx->ipv6) { + for (mssind = ARRAY_SIZE(msstab6) - 1; mssind; mssind--) + if (ctx->attrs.mss >= msstab6[mssind]) + break; + + ctx->attrs.mss = msstab6[mssind]; + + first = (u64)ctx->ipv6->saddr.in6_u.u6_addr8[0] << 32 | + ctx->ipv6->daddr.in6_u.u6_addr32[0]; + } + + second = (u64)seq << 32 | ctx->tcp->source << 16 | ctx->tcp->dest; + hash = siphash_2u64(first, second, &test_key_siphash); + + if (ctx->attrs.tstamp_ok) { + ctx->attrs.rcv_tsecr = bpf_get_prandom_u32(); + ctx->attrs.rcv_tsecr &= ~COOKIE_MASK; + ctx->attrs.rcv_tsecr |= hash & COOKIE_MASK; + } + + hash &= ~COOKIE_MASK; + hash |= mssind << 6; + + if (ctx->attrs.wscale_ok) + hash |= ctx->attrs.snd_wscale & BPF_SYNCOOKIE_WSCALE_MASK; + + if (ctx->attrs.sack_ok) + hash |= BPF_SYNCOOKIE_SACK; + + if (ctx->attrs.tstamp_ok && ctx->tcp->ece && ctx->tcp->cwr) + hash |= BPF_SYNCOOKIE_ECN; + + ctx->cookie = hash; +} + +static void tcp_write_options(struct tcp_syncookie *ctx) +{ + ctx->ptr32 = (__be32 *)(ctx->tcp + 1); + + *ctx->ptr32++ = bpf_htonl(TCPOPT_MSS << 24 | TCPOLEN_MSS << 16 | + ctx->attrs.mss); + + if (ctx->attrs.wscale_ok) + *ctx->ptr32++ = bpf_htonl(TCPOPT_NOP << 24 | + TCPOPT_WINDOW << 16 | + TCPOLEN_WINDOW << 8 | + ctx->attrs.snd_wscale); + + if (ctx->attrs.tstamp_ok) { + if (ctx->attrs.sack_ok) + *ctx->ptr32++ = bpf_htonl(TCPOPT_SACK_PERM << 24 | + TCPOLEN_SACK_PERM << 16 | + TCPOPT_TIMESTAMP << 8 | + TCPOLEN_TIMESTAMP); + else + *ctx->ptr32++ = bpf_htonl(TCPOPT_NOP << 24 | + TCPOPT_NOP << 16 | + TCPOPT_TIMESTAMP << 8 | + TCPOLEN_TIMESTAMP); + + *ctx->ptr32++ = bpf_htonl(ctx->attrs.rcv_tsecr); + *ctx->ptr32++ = bpf_htonl(ctx->attrs.rcv_tsval); + } else if (ctx->attrs.sack_ok) { + *ctx->ptr32++ = bpf_htonl(TCPOPT_NOP << 24 | + TCPOPT_NOP << 16 | + TCPOPT_SACK_PERM << 8 | + TCPOLEN_SACK_PERM); + } +} + +static int tcp_handle_syn(struct tcp_syncookie *ctx) +{ + s64 csum; + + if (tcp_validate_header(ctx)) + goto err; + + tcp_parse_options(ctx); + + if (tcp_validate_sysctl(ctx)) + goto err; + + tcp_prepare_cookie(ctx); + tcp_write_options(ctx); + + swap(ctx->tcp->source, ctx->tcp->dest); + ctx->tcp->check = 0; + ctx->tcp->ack_seq = bpf_htonl(bpf_ntohl(ctx->tcp->seq) + 1); + ctx->tcp->seq = bpf_htonl(ctx->cookie); + ctx->tcp->doff = ((long)ctx->ptr32 - (long)ctx->tcp) >> 2; + ctx->tcp->ack = 1; + if (!ctx->attrs.tstamp_ok || !ctx->tcp->ece || !ctx->tcp->cwr) + ctx->tcp->ece = 0; + ctx->tcp->cwr = 0; + + csum = bpf_csum_diff(0, 0, (void *)ctx->tcp, ctx->tcp->doff * 4, 0); + if (csum < 0) + goto err; + + if (ctx->ipv4) { + swap(ctx->ipv4->saddr, ctx->ipv4->daddr); + ctx->tcp->check = tcp_v4_csum(ctx, csum); + + ctx->ipv4->check = 0; + ctx->ipv4->tos = 0; + ctx->ipv4->tot_len = bpf_htons((long)ctx->ptr32 - (long)ctx->ipv4); + ctx->ipv4->id = 0; + ctx->ipv4->ttl = 64; + + csum = bpf_csum_diff(0, 0, (void *)ctx->ipv4, sizeof(*ctx->ipv4), 0); + if (csum < 0) + goto err; + + ctx->ipv4->check = csum_fold(csum); + } else if (ctx->ipv6) { + swap(ctx->ipv6->saddr, ctx->ipv6->daddr); + ctx->tcp->check = tcp_v6_csum(ctx, csum); + + *(__be32 *)ctx->ipv6 = bpf_htonl(0x60000000); + ctx->ipv6->payload_len = bpf_htons((long)ctx->ptr32 - (long)ctx->tcp); + ctx->ipv6->hop_limit = 64; + } + + swap_array(ctx->eth->h_source, ctx->eth->h_dest); + + if (bpf_skb_change_tail(ctx->skb, (long)ctx->ptr32 - (long)ctx->eth, 0)) + goto err; + + return bpf_redirect(ctx->skb->ifindex, 0); +err: + return TC_ACT_SHOT; +} + +static int tcp_validate_cookie(struct tcp_syncookie *ctx) +{ + u32 cookie = bpf_ntohl(ctx->tcp->ack_seq) - 1; + u32 seq = bpf_ntohl(ctx->tcp->seq) - 1; + u64 first = 0, second; + int mssind; + u32 hash; + + if (ctx->ipv4) + first = (u64)ctx->ipv4->saddr << 32 | ctx->ipv4->daddr; + else if (ctx->ipv6) + first = (u64)ctx->ipv6->saddr.in6_u.u6_addr8[0] << 32 | + ctx->ipv6->daddr.in6_u.u6_addr32[0]; + + second = (u64)seq << 32 | ctx->tcp->source << 16 | ctx->tcp->dest; + hash = siphash_2u64(first, second, &test_key_siphash); + + if (ctx->attrs.tstamp_ok) + hash -= ctx->attrs.rcv_tsecr & COOKIE_MASK; + else + hash &= ~COOKIE_MASK; + + hash -= cookie & ~COOKIE_MASK; + if (hash) + goto err; + + mssind = (cookie & (3 << 6)) >> 6; + if (ctx->ipv4) { + if (mssind > ARRAY_SIZE(msstab4)) + goto err; + + ctx->attrs.mss = msstab4[mssind]; + } else { + if (mssind > ARRAY_SIZE(msstab6)) + goto err; + + ctx->attrs.mss = msstab6[mssind]; + } + + ctx->attrs.snd_wscale = cookie & BPF_SYNCOOKIE_WSCALE_MASK; + ctx->attrs.rcv_wscale = ctx->attrs.snd_wscale; + ctx->attrs.wscale_ok = ctx->attrs.snd_wscale == BPF_SYNCOOKIE_WSCALE_MASK; + ctx->attrs.sack_ok = cookie & BPF_SYNCOOKIE_SACK; + ctx->attrs.ecn_ok = cookie & BPF_SYNCOOKIE_ECN; + + return 0; +err: + return -1; +} + +static int tcp_handle_ack(struct tcp_syncookie *ctx) +{ + struct bpf_sock_tuple tuple; + struct bpf_sock *skc; + int ret = TC_ACT_OK; + struct sock *sk; + u32 tuple_size; + + if (ctx->ipv4) { + tuple.ipv4.saddr = ctx->ipv4->saddr; + tuple.ipv4.daddr = ctx->ipv4->daddr; + tuple.ipv4.sport = ctx->tcp->source; + tuple.ipv4.dport = ctx->tcp->dest; + tuple_size = sizeof(tuple.ipv4); + } else if (ctx->ipv6) { + __builtin_memcpy(tuple.ipv6.saddr, &ctx->ipv6->saddr, sizeof(tuple.ipv6.saddr)); + __builtin_memcpy(tuple.ipv6.daddr, &ctx->ipv6->daddr, sizeof(tuple.ipv6.daddr)); + tuple.ipv6.sport = ctx->tcp->source; + tuple.ipv6.dport = ctx->tcp->dest; + tuple_size = sizeof(tuple.ipv6); + } else { + goto out; + } + + skc = bpf_skc_lookup_tcp(ctx->skb, &tuple, tuple_size, -1, 0); + if (!skc) + goto out; + + if (skc->state != TCP_LISTEN) + goto release; + + sk = (struct sock *)bpf_skc_to_tcp_sock(skc); + if (!sk) + goto err; + + if (tcp_validate_header(ctx)) + goto err; + + tcp_parse_options(ctx); + + if (tcp_validate_cookie(ctx)) + goto err; + + ret = bpf_sk_assign_tcp_reqsk(ctx->skb, sk, &ctx->attrs, sizeof(ctx->attrs)); + if (ret < 0) + goto err; + +release: + bpf_sk_release(skc); +out: + return ret; + +err: + ret = TC_ACT_SHOT; + goto release; +} + +SEC("tc") +int tcp_custom_syncookie(struct __sk_buff *skb) +{ + struct tcp_syncookie ctx = { + .skb = skb, + }; + + if (tcp_load_headers(&ctx)) + return TC_ACT_OK; + + if (ctx.tcp->rst) + return TC_ACT_OK; + + if (ctx.tcp->syn) { + if (ctx.tcp->ack) + return TC_ACT_OK; + + handled_syn = true; + + return tcp_handle_syn(&ctx); + } + + handled_ack = true; + + return tcp_handle_ack(&ctx); +} + +char _license[] SEC("license") = "GPL"; |