| #include <linux/err.h> |
| #include <linux/init.h> |
| #include <linux/kernel.h> |
| #include <linux/list.h> |
| #include <linux/tcp.h> |
| #include <linux/rcupdate.h> |
| #include <linux/rculist.h> |
| #include <net/inetpeer.h> |
| #include <net/tcp.h> |
| |
| int sysctl_tcp_fastopen __read_mostly = TFO_CLIENT_ENABLE; |
| |
| struct tcp_fastopen_context __rcu *tcp_fastopen_ctx; |
| |
| static DEFINE_SPINLOCK(tcp_fastopen_ctx_lock); |
| |
| void tcp_fastopen_init_key_once(bool publish) |
| { |
| static u8 key[TCP_FASTOPEN_KEY_LENGTH]; |
| |
| /* tcp_fastopen_reset_cipher publishes the new context |
| * atomically, so we allow this race happening here. |
| * |
| * All call sites of tcp_fastopen_cookie_gen also check |
| * for a valid cookie, so this is an acceptable risk. |
| */ |
| if (net_get_random_once(key, sizeof(key)) && publish) |
| tcp_fastopen_reset_cipher(key, sizeof(key)); |
| } |
| |
| static void tcp_fastopen_ctx_free(struct rcu_head *head) |
| { |
| struct tcp_fastopen_context *ctx = |
| container_of(head, struct tcp_fastopen_context, rcu); |
| crypto_free_cipher(ctx->tfm); |
| kfree(ctx); |
| } |
| |
| int tcp_fastopen_reset_cipher(void *key, unsigned int len) |
| { |
| int err; |
| struct tcp_fastopen_context *ctx, *octx; |
| |
| ctx = kmalloc(sizeof(*ctx), GFP_KERNEL); |
| if (!ctx) |
| return -ENOMEM; |
| ctx->tfm = crypto_alloc_cipher("aes", 0, 0); |
| |
| if (IS_ERR(ctx->tfm)) { |
| err = PTR_ERR(ctx->tfm); |
| error: kfree(ctx); |
| pr_err("TCP: TFO aes cipher alloc error: %d\n", err); |
| return err; |
| } |
| err = crypto_cipher_setkey(ctx->tfm, key, len); |
| if (err) { |
| pr_err("TCP: TFO cipher key error: %d\n", err); |
| crypto_free_cipher(ctx->tfm); |
| goto error; |
| } |
| memcpy(ctx->key, key, len); |
| |
| spin_lock(&tcp_fastopen_ctx_lock); |
| |
| octx = rcu_dereference_protected(tcp_fastopen_ctx, |
| lockdep_is_held(&tcp_fastopen_ctx_lock)); |
| rcu_assign_pointer(tcp_fastopen_ctx, ctx); |
| spin_unlock(&tcp_fastopen_ctx_lock); |
| |
| if (octx) |
| call_rcu(&octx->rcu, tcp_fastopen_ctx_free); |
| return err; |
| } |
| |
| static bool __tcp_fastopen_cookie_gen(const void *path, |
| struct tcp_fastopen_cookie *foc) |
| { |
| struct tcp_fastopen_context *ctx; |
| bool ok = false; |
| |
| tcp_fastopen_init_key_once(true); |
| |
| rcu_read_lock(); |
| ctx = rcu_dereference(tcp_fastopen_ctx); |
| if (ctx) { |
| crypto_cipher_encrypt_one(ctx->tfm, foc->val, path); |
| foc->len = TCP_FASTOPEN_COOKIE_SIZE; |
| ok = true; |
| } |
| rcu_read_unlock(); |
| return ok; |
| } |
| |
| /* Generate the fastopen cookie by doing aes128 encryption on both |
| * the source and destination addresses. Pad 0s for IPv4 or IPv4-mapped-IPv6 |
| * addresses. For the longer IPv6 addresses use CBC-MAC. |
| * |
| * XXX (TFO) - refactor when TCP_FASTOPEN_COOKIE_SIZE != AES_BLOCK_SIZE. |
| */ |
| static bool tcp_fastopen_cookie_gen(struct request_sock *req, |
| struct sk_buff *syn, |
| struct tcp_fastopen_cookie *foc) |
| { |
| if (req->rsk_ops->family == AF_INET) { |
| const struct iphdr *iph = ip_hdr(syn); |
| |
| __be32 path[4] = { iph->saddr, iph->daddr, 0, 0 }; |
| return __tcp_fastopen_cookie_gen(path, foc); |
| } |
| |
| #if IS_ENABLED(CONFIG_IPV6) |
| if (req->rsk_ops->family == AF_INET6) { |
| const struct ipv6hdr *ip6h = ipv6_hdr(syn); |
| struct tcp_fastopen_cookie tmp; |
| |
| if (__tcp_fastopen_cookie_gen(&ip6h->saddr, &tmp)) { |
| struct in6_addr *buf = (struct in6_addr *) tmp.val; |
| int i; |
| |
| for (i = 0; i < 4; i++) |
| buf->s6_addr32[i] ^= ip6h->daddr.s6_addr32[i]; |
| return __tcp_fastopen_cookie_gen(buf, foc); |
| } |
| } |
| #endif |
| return false; |
| } |
| |
| static bool tcp_fastopen_create_child(struct sock *sk, |
| struct sk_buff *skb, |
| struct dst_entry *dst, |
| struct request_sock *req) |
| { |
| struct tcp_sock *tp; |
| struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue; |
| struct sock *child; |
| u32 end_seq; |
| |
| req->num_retrans = 0; |
| req->num_timeout = 0; |
| req->sk = NULL; |
| |
| child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL); |
| if (!child) |
| return false; |
| |
| spin_lock(&queue->fastopenq->lock); |
| queue->fastopenq->qlen++; |
| spin_unlock(&queue->fastopenq->lock); |
| |
| /* Initialize the child socket. Have to fix some values to take |
| * into account the child is a Fast Open socket and is created |
| * only out of the bits carried in the SYN packet. |
| */ |
| tp = tcp_sk(child); |
| |
| tp->fastopen_rsk = req; |
| tcp_rsk(req)->tfo_listener = true; |
| |
| /* RFC1323: The window in SYN & SYN/ACK segments is never |
| * scaled. So correct it appropriately. |
| */ |
| tp->snd_wnd = ntohs(tcp_hdr(skb)->window); |
| |
| /* Activate the retrans timer so that SYNACK can be retransmitted. |
| * The request socket is not added to the SYN table of the parent |
| * because it's been added to the accept queue directly. |
| */ |
| inet_csk_reset_xmit_timer(child, ICSK_TIME_RETRANS, |
| TCP_TIMEOUT_INIT, TCP_RTO_MAX); |
| |
| atomic_set(&req->rsk_refcnt, 1); |
| /* Add the child socket directly into the accept queue */ |
| inet_csk_reqsk_queue_add(sk, req, child); |
| |
| /* Now finish processing the fastopen child socket. */ |
| inet_csk(child)->icsk_af_ops->rebuild_header(child); |
| tcp_init_congestion_control(child); |
| tcp_mtup_init(child); |
| tcp_init_metrics(child); |
| tcp_init_buffer_space(child); |
| |
| /* Queue the data carried in the SYN packet. We need to first |
| * bump skb's refcnt because the caller will attempt to free it. |
| * Note that IPv6 might also have used skb_get() trick |
| * in tcp_v6_conn_request() to keep this SYN around (treq->pktopts) |
| * So we need to eventually get a clone of the packet, |
| * before inserting it in sk_receive_queue. |
| * |
| * XXX (TFO) - we honor a zero-payload TFO request for now, |
| * (any reason not to?) but no need to queue the skb since |
| * there is no data. How about SYN+FIN? |
| */ |
| end_seq = TCP_SKB_CB(skb)->end_seq; |
| if (end_seq != TCP_SKB_CB(skb)->seq + 1) { |
| struct sk_buff *skb2; |
| |
| if (unlikely(skb_shared(skb))) |
| skb2 = skb_clone(skb, GFP_ATOMIC); |
| else |
| skb2 = skb_get(skb); |
| |
| if (likely(skb2)) { |
| skb_dst_drop(skb2); |
| __skb_pull(skb2, tcp_hdrlen(skb)); |
| skb_set_owner_r(skb2, child); |
| __skb_queue_tail(&child->sk_receive_queue, skb2); |
| tp->syn_data_acked = 1; |
| } else { |
| end_seq = TCP_SKB_CB(skb)->seq + 1; |
| } |
| } |
| tcp_rsk(req)->rcv_nxt = tp->rcv_nxt = end_seq; |
| sk->sk_data_ready(sk); |
| bh_unlock_sock(child); |
| sock_put(child); |
| WARN_ON(!req->sk); |
| return true; |
| } |
| |
| static bool tcp_fastopen_queue_check(struct sock *sk) |
| { |
| struct fastopen_queue *fastopenq; |
| |
| /* Make sure the listener has enabled fastopen, and we don't |
| * exceed the max # of pending TFO requests allowed before trying |
| * to validating the cookie in order to avoid burning CPU cycles |
| * unnecessarily. |
| * |
| * XXX (TFO) - The implication of checking the max_qlen before |
| * processing a cookie request is that clients can't differentiate |
| * between qlen overflow causing Fast Open to be disabled |
| * temporarily vs a server not supporting Fast Open at all. |
| */ |
| fastopenq = inet_csk(sk)->icsk_accept_queue.fastopenq; |
| if (!fastopenq || fastopenq->max_qlen == 0) |
| return false; |
| |
| if (fastopenq->qlen >= fastopenq->max_qlen) { |
| struct request_sock *req1; |
| spin_lock(&fastopenq->lock); |
| req1 = fastopenq->rskq_rst_head; |
| if (!req1 || time_after(req1->rsk_timer.expires, jiffies)) { |
| spin_unlock(&fastopenq->lock); |
| NET_INC_STATS_BH(sock_net(sk), |
| LINUX_MIB_TCPFASTOPENLISTENOVERFLOW); |
| return false; |
| } |
| fastopenq->rskq_rst_head = req1->dl_next; |
| fastopenq->qlen--; |
| spin_unlock(&fastopenq->lock); |
| reqsk_put(req1); |
| } |
| return true; |
| } |
| |
| /* Returns true if we should perform Fast Open on the SYN. The cookie (foc) |
| * may be updated and return the client in the SYN-ACK later. E.g., Fast Open |
| * cookie request (foc->len == 0). |
| */ |
| bool tcp_try_fastopen(struct sock *sk, struct sk_buff *skb, |
| struct request_sock *req, |
| struct tcp_fastopen_cookie *foc, |
| struct dst_entry *dst) |
| { |
| struct tcp_fastopen_cookie valid_foc = { .len = -1 }; |
| bool syn_data = TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq + 1; |
| |
| if (foc->len == 0) /* Client requests a cookie */ |
| NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENCOOKIEREQD); |
| |
| if (!((sysctl_tcp_fastopen & TFO_SERVER_ENABLE) && |
| (syn_data || foc->len >= 0) && |
| tcp_fastopen_queue_check(sk))) { |
| foc->len = -1; |
| return false; |
| } |
| |
| if (syn_data && (sysctl_tcp_fastopen & TFO_SERVER_COOKIE_NOT_REQD)) |
| goto fastopen; |
| |
| if (foc->len >= 0 && /* Client presents or requests a cookie */ |
| tcp_fastopen_cookie_gen(req, skb, &valid_foc) && |
| foc->len == TCP_FASTOPEN_COOKIE_SIZE && |
| foc->len == valid_foc.len && |
| !memcmp(foc->val, valid_foc.val, foc->len)) { |
| /* Cookie is valid. Create a (full) child socket to accept |
| * the data in SYN before returning a SYN-ACK to ack the |
| * data. If we fail to create the socket, fall back and |
| * ack the ISN only but includes the same cookie. |
| * |
| * Note: Data-less SYN with valid cookie is allowed to send |
| * data in SYN_RECV state. |
| */ |
| fastopen: |
| if (tcp_fastopen_create_child(sk, skb, dst, req)) { |
| foc->len = -1; |
| NET_INC_STATS_BH(sock_net(sk), |
| LINUX_MIB_TCPFASTOPENPASSIVE); |
| return true; |
| } |
| NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENPASSIVEFAIL); |
| } else if (foc->len > 0) /* Client presents an invalid cookie */ |
| NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENPASSIVEFAIL); |
| |
| *foc = valid_foc; |
| return false; |
| } |
| EXPORT_SYMBOL(tcp_try_fastopen); |