tcp: TCP Fast Open Server - header & support functions
This patch adds all the necessary data structure and support
functions to implement TFO server side. It also documents a number
of flags for the sysctl_tcp_fastopen knob, and adds a few Linux
extension MIBs.
In addition, it includes the following:
1. a new TCP_FASTOPEN socket option an application must call to
supply a max backlog allowed in order to enable TFO on its listener.
2. A number of key data structures:
"fastopen_rsk" in tcp_sock - for a big socket to access its
request_sock for retransmission and ack processing purpose. It is
non-NULL iff 3WHS not completed.
"fastopenq" in request_sock_queue - points to a per Fast Open
listener data structure "fastopen_queue" to keep track of qlen (# of
outstanding Fast Open requests) and max_qlen, among other things.
"listener" in tcp_request_sock - to point to the original listener
for book-keeping purpose, i.e., to maintain qlen against max_qlen
as part of defense against IP spoofing attack.
3. various data structure and functions, many in tcp_fastopen.c, to
support server side Fast Open cookie operations, including
/proc/sys/net/ipv4/tcp_fastopen_key to allow manual rekeying.
Signed-off-by: H.K. Jerry Chu <hkchu@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c
index a7f729c..8f7ef0a 100644
--- a/net/ipv4/tcp_fastopen.c
+++ b/net/ipv4/tcp_fastopen.c
@@ -1,10 +1,91 @@
+#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;
+int sysctl_tcp_fastopen __read_mostly;
+
+struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
+
+static DEFINE_SPINLOCK(tcp_fastopen_ctx_lock);
+
+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;
+}
+
+/* Computes the fastopen cookie for the peer.
+ * The peer address 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 addr, struct tcp_fastopen_cookie *foc)
+{
+ __be32 peer_addr[4] = { addr, 0, 0, 0 };
+ struct tcp_fastopen_context *ctx;
+
+ rcu_read_lock();
+ ctx = rcu_dereference(tcp_fastopen_ctx);
+ if (ctx) {
+ crypto_cipher_encrypt_one(ctx->tfm,
+ foc->val,
+ (__u8 *)peer_addr);
+ foc->len = TCP_FASTOPEN_COOKIE_SIZE;
+ }
+ rcu_read_unlock();
+}
static int __init tcp_fastopen_init(void)
{
+ __u8 key[TCP_FASTOPEN_KEY_LENGTH];
+
+ get_random_bytes(key, sizeof(key));
+ tcp_fastopen_reset_cipher(key, sizeof(key));
return 0;
}