1 files changed, 209 insertions, 10 deletions

diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c
index f195d9316e55..62e48cf84e60 100644
--- a/net/ipv4/tcp_fastopen.c
+++ b/net/ipv4/tcp_fastopen.c
@@ -72,25 +72,224 @@ error:		kfree(ctx);
         return err;
 }
 
-/* Computes the fastopen cookie for the IP path.
- * The path is a 128 bits long (pad with zeros for IPv4).
- *
- * The caller must check foc->len to determine if a valid cookie
- * has been generated successfully.
-*/
-void tcp_fastopen_cookie_gen(__be32 src, __be32 dst,
-                             struct tcp_fastopen_cookie *foc)
+static bool __tcp_fastopen_cookie_gen(const void *path,
+                                      struct tcp_fastopen_cookie *foc)
 {
-        __be32 path[4] = { src, dst, 0, 0 };
         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, (__u8 *)path);
+                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 = 4;
+
+                        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 = tcp_sk(sk);
+        struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
+        struct sock *child;
+
+        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 == NULL)
+                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;
+        /* Do a hold on the listner sk so that if the listener is being
+         * closed, the child that has been accepted can live on and still
+         * access listen_lock.
+         */
+        sock_hold(sk);
+        tcp_rsk(req)->listener = sk;
+
+        /* 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);
+
+        /* 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.
+         *
+         * 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?
+         */
+        if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq + 1) {
+                skb = skb_get(skb);
+                skb_dst_drop(skb);
+                __skb_pull(skb, tcp_hdr(skb)->doff * 4);
+                skb_set_owner_r(skb, child);
+                __skb_queue_tail(&child->sk_receive_queue, skb);
+                tp->syn_data_acked = 1;
+        }
+        tcp_rsk(req)->rcv_nxt = tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
+        sk->sk_data_ready(sk);
+        bh_unlock_sock(child);
+        sock_put(child);
+        WARN_ON(req->sk == NULL);
+        return true;
+}
+EXPORT_SYMBOL(tcp_fastopen_create_child);
+
+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 == NULL || 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 == NULL) || time_after(req1->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_free(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 (!((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 (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), foc->len ?
+                         LINUX_MIB_TCPFASTOPENPASSIVEFAIL :
+                         LINUX_MIB_TCPFASTOPENCOOKIEREQD);
+        *foc = valid_foc;
+        return false;
 }
+EXPORT_SYMBOL(tcp_try_fastopen);