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Release 4.14 net/ipv4/tcp_fastopen.c

Directory: net/ipv4
// SPDX-License-Identifier: GPL-2.0
#include <linux/crypto.h>
#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)); }


Hannes Frederic Sowa40100.00%1100.00%

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); }


Jerry Chu38100.00%1100.00%

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; }


Jerry Chu192100.00%1100.00%

static bool __tcp_fastopen_cookie_gen(const void *path, struct tcp_fastopen_cookie *foc) { struct tcp_fastopen_context *ctx; bool ok = false; 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; }


Jerry Chu5070.42%133.33%
Daniel Lee2028.17%133.33%
Yuchung Cheng11.41%133.33%

/* 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 = &tmp.addr; 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; }


Daniel Lee17298.29%133.33%
Shannon Nelson21.14%133.33%
Jerry Chu10.57%133.33%

/* If an incoming SYN or SYNACK frame contains a payload and/or FIN, * queue this additional data / FIN. */
void tcp_fastopen_add_skb(struct sock *sk, struct sk_buff *skb) { struct tcp_sock *tp = tcp_sk(sk); if (TCP_SKB_CB(skb)->end_seq == tp->rcv_nxt) return; skb = skb_clone(skb, GFP_ATOMIC); if (!skb) return; skb_dst_drop(skb); /* segs_in has been initialized to 1 in tcp_create_openreq_child(). * Hence, reset segs_in to 0 before calling tcp_segs_in() * to avoid double counting. Also, tcp_segs_in() expects * skb->len to include the tcp_hdrlen. Hence, it should * be called before __skb_pull(). */ tp->segs_in = 0; tcp_segs_in(tp, skb); __skb_pull(skb, tcp_hdrlen(skb)); sk_forced_mem_schedule(sk, skb->truesize); skb_set_owner_r(skb, sk); TCP_SKB_CB(skb)->seq++; TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_SYN; tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; __skb_queue_tail(&sk->sk_receive_queue, skb); tp->syn_data_acked = 1; /* u64_stats_update_begin(&tp->syncp) not needed here, * as we certainly are not changing upper 32bit value (0) */ tp->bytes_received = skb->len; if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) tcp_fin(sk); }


Eric Dumazet15591.72%480.00%
Martin KaFai Lau148.28%120.00%

static struct sock *tcp_fastopen_create_child(struct sock *sk, struct sk_buff *skb, struct request_sock *req) { struct tcp_sock *tp; struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue; struct sock *child; bool own_req; 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, NULL, &own_req); if (!child) return NULL; 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); tp->max_window = tp->snd_wnd; /* Activate the retrans timer so that SYNACK can be retransmitted. * The request socket is not added to the ehash * 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); refcount_set(&req->rsk_refcnt, 2); /* 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_call_bpf(child, BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB); tcp_init_buffer_space(child); tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; tcp_fastopen_add_skb(child, skb); tcp_rsk(req)->rcv_nxt = tp->rcv_nxt; tp->rcv_wup = tp->rcv_nxt; /* tcp_conn_request() is sending the SYNACK, * and queues the child into listener accept queue. */ return child; }


Yuchung Cheng21778.06%212.50%
Eric Dumazet3612.95%956.25%
Neal Cardwell82.88%16.25%
Alexey Kodanev82.88%16.25%
Lawrence Brakmo72.52%16.25%
Ian Morris10.36%16.25%
Elena Reshetova10.36%16.25%

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->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)) { __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENLISTENOVERFLOW); spin_unlock(&fastopenq->lock); return false; } fastopenq->rskq_rst_head = req1->dl_next; fastopenq->qlen--; spin_unlock(&fastopenq->lock); reqsk_put(req1); } return true; }


Yuchung Cheng12589.93%116.67%
Eric Dumazet1410.07%583.33%

/* 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). */
struct sock *tcp_try_fastopen(struct sock *sk, struct sk_buff *skb, struct request_sock *req, struct tcp_fastopen_cookie *foc) { struct tcp_fastopen_cookie valid_foc = { .len = -1 }; bool syn_data = TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq + 1; struct sock *child; if (foc->len == 0) /* Client requests a cookie */ NET_INC_STATS(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 NULL; } 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: child = tcp_fastopen_create_child(sk, skb, req); if (child) { foc->len = -1; NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENPASSIVE); return child; } NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENPASSIVEFAIL); } else if (foc->len > 0) /* Client presents an invalid cookie */ NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENPASSIVEFAIL); valid_foc.exp = foc->exp; *foc = valid_foc; return NULL; }


Yuchung Cheng23787.78%450.00%
Eric Dumazet217.78%225.00%
Daniel Lee124.44%225.00%

bool tcp_fastopen_cookie_check(struct sock *sk, u16 *mss, struct tcp_fastopen_cookie *cookie) { unsigned long last_syn_loss = 0; int syn_loss = 0; tcp_fastopen_cache_get(sk, mss, cookie, &syn_loss, &last_syn_loss); /* Recurring FO SYN losses: no cookie or data in SYN */ if (syn_loss > 1 && time_before(jiffies, last_syn_loss + (60*HZ << syn_loss))) { cookie->len = -1; return false; } /* Firewall blackhole issue check */ if (tcp_fastopen_active_should_disable(sk)) { cookie->len = -1; return false; } if (sysctl_tcp_fastopen & TFO_CLIENT_NO_COOKIE) { cookie->len = -1; return true; } return cookie->len > 0; }


Wei Wang124100.00%2100.00%

/* This function checks if we want to defer sending SYN until the first * write(). We defer under the following conditions: * 1. fastopen_connect sockopt is set * 2. we have a valid cookie * Return value: return true if we want to defer until application writes data * return false if we want to send out SYN immediately */
bool tcp_fastopen_defer_connect(struct sock *sk, int *err) { struct tcp_fastopen_cookie cookie = { .len = 0 }; struct tcp_sock *tp = tcp_sk(sk); u16 mss; if (tp->fastopen_connect && !tp->fastopen_req) { if (tcp_fastopen_cookie_check(sk, &mss, &cookie)) { inet_sk(sk)->defer_connect = 1; return true; } /* Alloc fastopen_req in order for FO option to be included * in SYN */ tp->fastopen_req = kzalloc(sizeof(*tp->fastopen_req), sk->sk_allocation); if (tp->fastopen_req) tp->fastopen_req->cookie = cookie; else *err = -ENOBUFS; } return false; }


Wei Wang122100.00%1100.00%

EXPORT_SYMBOL(tcp_fastopen_defer_connect); /* * The following code block is to deal with middle box issues with TFO: * Middlebox firewall issues can potentially cause server's data being * blackholed after a successful 3WHS using TFO. * The proposed solution is to disable active TFO globally under the * following circumstances: * 1. client side TFO socket receives out of order FIN * 2. client side TFO socket receives out of order RST * We disable active side TFO globally for 1hr at first. Then if it * happens again, we disable it for 2h, then 4h, 8h, ... * And we reset the timeout back to 1hr when we see a successful active * TFO connection with data exchanges. */ /* Default to 1hr */ unsigned int sysctl_tcp_fastopen_blackhole_timeout __read_mostly = 60 * 60; static atomic_t tfo_active_disable_times __read_mostly = ATOMIC_INIT(0); static unsigned long tfo_active_disable_stamp __read_mostly; /* Disable active TFO and record current jiffies and * tfo_active_disable_times */
void tcp_fastopen_active_disable(struct sock *sk) { atomic_inc(&tfo_active_disable_times); tfo_active_disable_stamp = jiffies; NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENBLACKHOLE); }


Wei Wang30100.00%2100.00%

/* Reset tfo_active_disable_times to 0 */
void tcp_fastopen_active_timeout_reset(void) { atomic_set(&tfo_active_disable_times, 0); }


Wei Wang15100.00%1100.00%

/* Calculate timeout for tfo active disable * Return true if we are still in the active TFO disable period * Return false if timeout already expired and we should use active TFO */
bool tcp_fastopen_active_should_disable(struct sock *sk) { int tfo_da_times = atomic_read(&tfo_active_disable_times); int multiplier; unsigned long timeout; if (!tfo_da_times) return false; /* Limit timout to max: 2^6 * initial timeout */ multiplier = 1 << min(tfo_da_times - 1, 6); timeout = multiplier * sysctl_tcp_fastopen_blackhole_timeout * HZ; if (time_before(jiffies, tfo_active_disable_stamp + timeout)) return true; /* Mark check bit so we can check for successful active TFO * condition and reset tfo_active_disable_times */ tcp_sk(sk)->syn_fastopen_ch = 1; return false; }


Wei Wang83100.00%1100.00%

/* Disable active TFO if FIN is the only packet in the ofo queue * and no data is received. * Also check if we can reset tfo_active_disable_times if data is * received successfully on a marked active TFO sockets opened on * a non-loopback interface */
void tcp_fastopen_active_disable_ofo_check(struct sock *sk) { struct tcp_sock *tp = tcp_sk(sk); struct rb_node *p; struct sk_buff *skb; struct dst_entry *dst; if (!tp->syn_fastopen) return; if (!tp->data_segs_in) { p = rb_first(&tp->out_of_order_queue); if (p && !rb_next(p)) { skb = rb_entry(p, struct sk_buff, rbnode); if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) { tcp_fastopen_active_disable(sk); return; } } } else if (tp->syn_fastopen_ch && atomic_read(&tfo_active_disable_times)) { dst = sk_dst_get(sk); if (!(dst && dst->dev && (dst->dev->flags & IFF_LOOPBACK))) tcp_fastopen_active_timeout_reset(); dst_release(dst); } }


Wei Wang156100.00%2100.00%

Overall Contributors

Yuchung Cheng59229.73%717.50%
Wei Wang56728.48%410.00%
Jerry Chu31515.82%12.50%
Eric Dumazet22711.40%1640.00%
Daniel Lee20510.30%25.00%
Hannes Frederic Sowa402.01%12.50%
Martin KaFai Lau140.70%12.50%
Alexey Kodanev80.40%12.50%
Neal Cardwell80.40%12.50%
Lawrence Brakmo70.35%12.50%
Herbert Xu30.15%12.50%
Shannon Nelson20.10%12.50%
Elena Reshetova10.05%12.50%
Ian Morris10.05%12.50%
Greg Kroah-Hartman10.05%12.50%
Directory: net/ipv4
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