[RFC PATCH 3/4] net: add uring_cmd callback to TCP

This is the implementation of uring_cmd for the TCP protocol. It
basically encompasses SOCKET_URING_OP_SIOCOUTQ and
SOCKET_URING_OP_SIOCINQ, which is similar to the SIOCOUTQ and SIOCINQ
ioctls.

The return value is exactly the same as the regular ioctl (tcp_ioctl()).

Signed-off-by: Breno Leitao <[email protected]>
---
 include/net/tcp.h   |  2 ++
 net/ipv4/tcp.c      | 32 ++++++++++++++++++++++++++++++++
 net/ipv4/tcp_ipv4.c |  1 +
 3 files changed, 35 insertions(+)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index db9f828e9d1e..4dfd6bd63261 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -342,6 +342,8 @@ void tcp_release_cb(struct sock *sk);
 void tcp_wfree(struct sk_buff *skb);
 void tcp_write_timer_handler(struct sock *sk);
 void tcp_delack_timer_handler(struct sock *sk);
+int tcp_uring_cmd(struct sock *sk, struct io_uring_cmd *cmd,
+		  unsigned int issue_flags);
 int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg);
 int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb);
 void tcp_rcv_established(struct sock *sk, struct sk_buff *skb);
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 288693981b00..cf2822242e28 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -279,6 +279,7 @@
 #include <linux/uaccess.h>
 #include <asm/ioctls.h>
 #include <net/busy_poll.h>
+#include <linux/io_uring.h>
 
 /* Track pending CMSGs. */
 enum {
@@ -596,6 +597,37 @@ __poll_t tcp_poll(struct file *file, struct socket *sock, poll_table *wait)
 }
 EXPORT_SYMBOL(tcp_poll);
 
+int tcp_uring_cmd(struct sock *sk, struct io_uring_cmd *cmd,
+		  unsigned int issue_flags)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	bool slow;
+	int ret;
+
+	switch (cmd->sqe->cmd_op) {
+	case SOCKET_URING_OP_SIOCINQ:
+		if (sk->sk_state = TCP_LISTEN)
+			return -EINVAL;
+
+		slow = lock_sock_fast(sk);
+		ret = tcp_inq(sk);
+		unlock_sock_fast(sk, slow);
+		return ret;
+	case SOCKET_URING_OP_SIOCOUTQ:
+		if (sk->sk_state = TCP_LISTEN)
+			return -EINVAL;
+
+		if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))
+			ret = 0;
+		else
+			ret = READ_ONCE(tp->write_seq) - tp->snd_una;
+		return ret;
+	default:
+		return -ENOIOCTLCMD;
+	}
+}
+EXPORT_SYMBOL_GPL(tcp_uring_cmd);
+
 int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index ea370afa70ed..900081fa2e1a 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -3103,6 +3103,7 @@ struct proto tcp_prot = {
 	.disconnect		= tcp_disconnect,
 	.accept			= inet_csk_accept,
 	.ioctl			= tcp_ioctl,
+	.uring_cmd		= tcp_uring_cmd,
 	.init			= tcp_v4_init_sock,
 	.destroy		= tcp_v4_destroy_sock,
 	.shutdown		= tcp_shutdown,
-- 
2.34.1