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synced 2024-10-29 23:53:32 +00:00
dfea2aa654
tcp_fastopen_reset_cipher really cannot be called from interrupt
context. It allocates the tcp_fastopen_context with GFP_KERNEL and
calls crypto_alloc_cipher, which allocates all kind of stuff with
GFP_KERNEL.
Thus, we might sleep when the key-generation is triggered by an
incoming TFO cookie-request which would then happen in interrupt-
context, as shown by enabling CONFIG_DEBUG_ATOMIC_SLEEP:
[ 36.001813] BUG: sleeping function called from invalid context at mm/slub.c:1266
[ 36.003624] in_atomic(): 1, irqs_disabled(): 0, pid: 1016, name: packetdrill
[ 36.004859] CPU: 1 PID: 1016 Comm: packetdrill Not tainted 4.1.0-rc7 #14
[ 36.006085] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.7.5-0-ge51488c-20140602_164612-nilsson.home.kraxel.org 04/01/2014
[ 36.008250] 00000000000004f2 ffff88007f8838a8 ffffffff8171d53a ffff880075a084a8
[ 36.009630] ffff880075a08000 ffff88007f8838c8 ffffffff810967d3 ffff88007f883928
[ 36.011076] 0000000000000000 ffff88007f8838f8 ffffffff81096892 ffff88007f89be00
[ 36.012494] Call Trace:
[ 36.012953] <IRQ> [<ffffffff8171d53a>] dump_stack+0x4f/0x6d
[ 36.014085] [<ffffffff810967d3>] ___might_sleep+0x103/0x170
[ 36.015117] [<ffffffff81096892>] __might_sleep+0x52/0x90
[ 36.016117] [<ffffffff8118e887>] kmem_cache_alloc_trace+0x47/0x190
[ 36.017266] [<ffffffff81680d82>] ? tcp_fastopen_reset_cipher+0x42/0x130
[ 36.018485] [<ffffffff81680d82>] tcp_fastopen_reset_cipher+0x42/0x130
[ 36.019679] [<ffffffff81680f01>] tcp_fastopen_init_key_once+0x61/0x70
[ 36.020884] [<ffffffff81680f2c>] __tcp_fastopen_cookie_gen+0x1c/0x60
[ 36.022058] [<ffffffff816814ff>] tcp_try_fastopen+0x58f/0x730
[ 36.023118] [<ffffffff81671788>] tcp_conn_request+0x3e8/0x7b0
[ 36.024185] [<ffffffff810e3872>] ? __module_text_address+0x12/0x60
[ 36.025327] [<ffffffff8167b2e1>] tcp_v4_conn_request+0x51/0x60
[ 36.026410] [<ffffffff816727e0>] tcp_rcv_state_process+0x190/0xda0
[ 36.027556] [<ffffffff81661f97>] ? __inet_lookup_established+0x47/0x170
[ 36.028784] [<ffffffff8167c2ad>] tcp_v4_do_rcv+0x16d/0x3d0
[ 36.029832] [<ffffffff812e6806>] ? security_sock_rcv_skb+0x16/0x20
[ 36.030936] [<ffffffff8167cc8a>] tcp_v4_rcv+0x77a/0x7b0
[ 36.031875] [<ffffffff816af8c3>] ? iptable_filter_hook+0x33/0x70
[ 36.032953] [<ffffffff81657d22>] ip_local_deliver_finish+0x92/0x1f0
[ 36.034065] [<ffffffff81657f1a>] ip_local_deliver+0x9a/0xb0
[ 36.035069] [<ffffffff81657c90>] ? ip_rcv+0x3d0/0x3d0
[ 36.035963] [<ffffffff81657569>] ip_rcv_finish+0x119/0x330
[ 36.036950] [<ffffffff81657ba7>] ip_rcv+0x2e7/0x3d0
[ 36.037847] [<ffffffff81610652>] __netif_receive_skb_core+0x552/0x930
[ 36.038994] [<ffffffff81610a57>] __netif_receive_skb+0x27/0x70
[ 36.040033] [<ffffffff81610b72>] process_backlog+0xd2/0x1f0
[ 36.041025] [<ffffffff81611482>] net_rx_action+0x122/0x310
[ 36.042007] [<ffffffff81076743>] __do_softirq+0x103/0x2f0
[ 36.042978] [<ffffffff81723e3c>] do_softirq_own_stack+0x1c/0x30
This patch moves the call to tcp_fastopen_init_key_once to the places
where a listener socket creates its TFO-state, which always happens in
user-context (either from the setsockopt, or implicitly during the
listen()-call)
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
Fixes: 222e83d2e0
("tcp: switch tcp_fastopen key generation to net_get_random_once")
Signed-off-by: Christoph Paasch <cpaasch@apple.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
313 lines
9.1 KiB
C
313 lines
9.1 KiB
C
#include <linux/err.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/list.h>
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#include <linux/tcp.h>
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#include <linux/rcupdate.h>
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#include <linux/rculist.h>
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#include <net/inetpeer.h>
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#include <net/tcp.h>
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int sysctl_tcp_fastopen __read_mostly = TFO_CLIENT_ENABLE;
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struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
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static DEFINE_SPINLOCK(tcp_fastopen_ctx_lock);
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void tcp_fastopen_init_key_once(bool publish)
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{
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static u8 key[TCP_FASTOPEN_KEY_LENGTH];
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/* tcp_fastopen_reset_cipher publishes the new context
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* atomically, so we allow this race happening here.
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*
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* All call sites of tcp_fastopen_cookie_gen also check
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* for a valid cookie, so this is an acceptable risk.
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*/
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if (net_get_random_once(key, sizeof(key)) && publish)
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tcp_fastopen_reset_cipher(key, sizeof(key));
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}
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static void tcp_fastopen_ctx_free(struct rcu_head *head)
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{
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struct tcp_fastopen_context *ctx =
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container_of(head, struct tcp_fastopen_context, rcu);
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crypto_free_cipher(ctx->tfm);
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kfree(ctx);
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}
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int tcp_fastopen_reset_cipher(void *key, unsigned int len)
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{
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int err;
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struct tcp_fastopen_context *ctx, *octx;
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ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
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if (!ctx)
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return -ENOMEM;
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ctx->tfm = crypto_alloc_cipher("aes", 0, 0);
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if (IS_ERR(ctx->tfm)) {
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err = PTR_ERR(ctx->tfm);
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error: kfree(ctx);
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pr_err("TCP: TFO aes cipher alloc error: %d\n", err);
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return err;
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}
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err = crypto_cipher_setkey(ctx->tfm, key, len);
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if (err) {
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pr_err("TCP: TFO cipher key error: %d\n", err);
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crypto_free_cipher(ctx->tfm);
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goto error;
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}
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memcpy(ctx->key, key, len);
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spin_lock(&tcp_fastopen_ctx_lock);
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octx = rcu_dereference_protected(tcp_fastopen_ctx,
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lockdep_is_held(&tcp_fastopen_ctx_lock));
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rcu_assign_pointer(tcp_fastopen_ctx, ctx);
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spin_unlock(&tcp_fastopen_ctx_lock);
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if (octx)
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call_rcu(&octx->rcu, tcp_fastopen_ctx_free);
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return err;
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}
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static bool __tcp_fastopen_cookie_gen(const void *path,
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struct tcp_fastopen_cookie *foc)
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{
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struct tcp_fastopen_context *ctx;
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bool ok = false;
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rcu_read_lock();
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ctx = rcu_dereference(tcp_fastopen_ctx);
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if (ctx) {
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crypto_cipher_encrypt_one(ctx->tfm, foc->val, path);
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foc->len = TCP_FASTOPEN_COOKIE_SIZE;
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ok = true;
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}
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rcu_read_unlock();
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return ok;
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}
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/* Generate the fastopen cookie by doing aes128 encryption on both
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* the source and destination addresses. Pad 0s for IPv4 or IPv4-mapped-IPv6
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* addresses. For the longer IPv6 addresses use CBC-MAC.
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*
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* XXX (TFO) - refactor when TCP_FASTOPEN_COOKIE_SIZE != AES_BLOCK_SIZE.
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*/
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static bool tcp_fastopen_cookie_gen(struct request_sock *req,
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struct sk_buff *syn,
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struct tcp_fastopen_cookie *foc)
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{
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if (req->rsk_ops->family == AF_INET) {
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const struct iphdr *iph = ip_hdr(syn);
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__be32 path[4] = { iph->saddr, iph->daddr, 0, 0 };
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return __tcp_fastopen_cookie_gen(path, foc);
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}
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#if IS_ENABLED(CONFIG_IPV6)
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if (req->rsk_ops->family == AF_INET6) {
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const struct ipv6hdr *ip6h = ipv6_hdr(syn);
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struct tcp_fastopen_cookie tmp;
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if (__tcp_fastopen_cookie_gen(&ip6h->saddr, &tmp)) {
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struct in6_addr *buf = (struct in6_addr *) tmp.val;
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int i;
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for (i = 0; i < 4; i++)
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buf->s6_addr32[i] ^= ip6h->daddr.s6_addr32[i];
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return __tcp_fastopen_cookie_gen(buf, foc);
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}
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}
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#endif
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return false;
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}
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static bool tcp_fastopen_create_child(struct sock *sk,
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struct sk_buff *skb,
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struct dst_entry *dst,
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struct request_sock *req)
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{
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struct tcp_sock *tp;
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struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
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struct sock *child;
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u32 end_seq;
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req->num_retrans = 0;
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req->num_timeout = 0;
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req->sk = NULL;
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child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL);
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if (!child)
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return false;
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spin_lock(&queue->fastopenq->lock);
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queue->fastopenq->qlen++;
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spin_unlock(&queue->fastopenq->lock);
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/* Initialize the child socket. Have to fix some values to take
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* into account the child is a Fast Open socket and is created
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* only out of the bits carried in the SYN packet.
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*/
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tp = tcp_sk(child);
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tp->fastopen_rsk = req;
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tcp_rsk(req)->tfo_listener = true;
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/* RFC1323: The window in SYN & SYN/ACK segments is never
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* scaled. So correct it appropriately.
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*/
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tp->snd_wnd = ntohs(tcp_hdr(skb)->window);
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/* Activate the retrans timer so that SYNACK can be retransmitted.
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* The request socket is not added to the SYN table of the parent
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* because it's been added to the accept queue directly.
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*/
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inet_csk_reset_xmit_timer(child, ICSK_TIME_RETRANS,
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TCP_TIMEOUT_INIT, TCP_RTO_MAX);
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atomic_set(&req->rsk_refcnt, 1);
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/* Add the child socket directly into the accept queue */
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inet_csk_reqsk_queue_add(sk, req, child);
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/* Now finish processing the fastopen child socket. */
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inet_csk(child)->icsk_af_ops->rebuild_header(child);
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tcp_init_congestion_control(child);
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tcp_mtup_init(child);
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tcp_init_metrics(child);
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tcp_init_buffer_space(child);
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/* Queue the data carried in the SYN packet. We need to first
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* bump skb's refcnt because the caller will attempt to free it.
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* Note that IPv6 might also have used skb_get() trick
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* in tcp_v6_conn_request() to keep this SYN around (treq->pktopts)
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* So we need to eventually get a clone of the packet,
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* before inserting it in sk_receive_queue.
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*
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* XXX (TFO) - we honor a zero-payload TFO request for now,
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* (any reason not to?) but no need to queue the skb since
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* there is no data. How about SYN+FIN?
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*/
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end_seq = TCP_SKB_CB(skb)->end_seq;
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if (end_seq != TCP_SKB_CB(skb)->seq + 1) {
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struct sk_buff *skb2;
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if (unlikely(skb_shared(skb)))
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skb2 = skb_clone(skb, GFP_ATOMIC);
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else
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skb2 = skb_get(skb);
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if (likely(skb2)) {
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skb_dst_drop(skb2);
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__skb_pull(skb2, tcp_hdrlen(skb));
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skb_set_owner_r(skb2, child);
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__skb_queue_tail(&child->sk_receive_queue, skb2);
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tp->syn_data_acked = 1;
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/* u64_stats_update_begin(&tp->syncp) not needed here,
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* as we certainly are not changing upper 32bit value (0)
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*/
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tp->bytes_received = end_seq - TCP_SKB_CB(skb)->seq - 1;
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} else {
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end_seq = TCP_SKB_CB(skb)->seq + 1;
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}
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}
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tcp_rsk(req)->rcv_nxt = tp->rcv_nxt = end_seq;
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sk->sk_data_ready(sk);
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bh_unlock_sock(child);
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sock_put(child);
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WARN_ON(!req->sk);
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return true;
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}
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static bool tcp_fastopen_queue_check(struct sock *sk)
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{
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struct fastopen_queue *fastopenq;
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/* Make sure the listener has enabled fastopen, and we don't
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* exceed the max # of pending TFO requests allowed before trying
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* to validating the cookie in order to avoid burning CPU cycles
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* unnecessarily.
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*
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* XXX (TFO) - The implication of checking the max_qlen before
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* processing a cookie request is that clients can't differentiate
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* between qlen overflow causing Fast Open to be disabled
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* temporarily vs a server not supporting Fast Open at all.
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*/
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fastopenq = inet_csk(sk)->icsk_accept_queue.fastopenq;
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if (!fastopenq || fastopenq->max_qlen == 0)
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return false;
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if (fastopenq->qlen >= fastopenq->max_qlen) {
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struct request_sock *req1;
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spin_lock(&fastopenq->lock);
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req1 = fastopenq->rskq_rst_head;
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if (!req1 || time_after(req1->rsk_timer.expires, jiffies)) {
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spin_unlock(&fastopenq->lock);
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NET_INC_STATS_BH(sock_net(sk),
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LINUX_MIB_TCPFASTOPENLISTENOVERFLOW);
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return false;
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}
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fastopenq->rskq_rst_head = req1->dl_next;
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fastopenq->qlen--;
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spin_unlock(&fastopenq->lock);
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reqsk_put(req1);
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}
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return true;
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}
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/* Returns true if we should perform Fast Open on the SYN. The cookie (foc)
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* may be updated and return the client in the SYN-ACK later. E.g., Fast Open
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* cookie request (foc->len == 0).
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*/
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bool tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
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struct request_sock *req,
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struct tcp_fastopen_cookie *foc,
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struct dst_entry *dst)
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{
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struct tcp_fastopen_cookie valid_foc = { .len = -1 };
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bool syn_data = TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq + 1;
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if (foc->len == 0) /* Client requests a cookie */
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NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENCOOKIEREQD);
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if (!((sysctl_tcp_fastopen & TFO_SERVER_ENABLE) &&
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(syn_data || foc->len >= 0) &&
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tcp_fastopen_queue_check(sk))) {
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foc->len = -1;
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return false;
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}
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if (syn_data && (sysctl_tcp_fastopen & TFO_SERVER_COOKIE_NOT_REQD))
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goto fastopen;
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if (foc->len >= 0 && /* Client presents or requests a cookie */
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tcp_fastopen_cookie_gen(req, skb, &valid_foc) &&
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foc->len == TCP_FASTOPEN_COOKIE_SIZE &&
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foc->len == valid_foc.len &&
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!memcmp(foc->val, valid_foc.val, foc->len)) {
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/* Cookie is valid. Create a (full) child socket to accept
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* the data in SYN before returning a SYN-ACK to ack the
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* data. If we fail to create the socket, fall back and
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* ack the ISN only but includes the same cookie.
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*
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* Note: Data-less SYN with valid cookie is allowed to send
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* data in SYN_RECV state.
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*/
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fastopen:
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if (tcp_fastopen_create_child(sk, skb, dst, req)) {
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foc->len = -1;
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NET_INC_STATS_BH(sock_net(sk),
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LINUX_MIB_TCPFASTOPENPASSIVE);
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return true;
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}
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NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENPASSIVEFAIL);
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} else if (foc->len > 0) /* Client presents an invalid cookie */
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NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENPASSIVEFAIL);
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valid_foc.exp = foc->exp;
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*foc = valid_foc;
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return false;
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}
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EXPORT_SYMBOL(tcp_try_fastopen);
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