tcp: Move connection state structures into a shared header

Currently spliced and non-spliced connections use completely independent
tracking structures.  We want to unify these, so as a preliminary step move
the definitions for both variants into a new tcp_conn.h header, shared by
tcp.c and tcp_splice.c.

This requires renaming some #defines with the same name but different
meanings between the two cases.  In the process we correct some places that
are slightly out of sync between the comments and the code for various
event bit names.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 168 insertions, 0 deletions

diff --git a/tcp_conn.h b/tcp_conn.h
new file mode 100644
index 0000000..db4c2d9
--- /dev/null
+++ b/tcp_conn.h
@@ -0,0 +1,168 @@
+/* SPDX-License-Identifier: AGPL-3.0-or-later
+ * Copyright Red Hat
+ * Author: Stefano Brivio <sbrivio@redhat.com>
+ * Author: David Gibson <david@gibson.dropbear.id.au>
+ *
+ * TCP connection tracking data structures, used by tcp.c and
+ * tcp_splice.c.  Shouldn't be included in non-TCP code.
+ */
+#ifndef TCP_CONN_H
+#define TCP_CONN_H
+
+#define TCP_HASH_BUCKET_BITS		(TCP_CONN_INDEX_BITS + 1)
+
+/**
+ * struct tcp_tap_conn - Descriptor for a TCP connection (not spliced)
+ * @next_index:		Connection index of next item in hash chain, -1 for none
+ * @tap_mss:		MSS advertised by tap/guest, rounded to 2 ^ TCP_MSS_BITS
+ * @sock:		Socket descriptor number
+ * @events:		Connection events, implying connection states
+ * @timer:		timerfd descriptor for timeout events
+ * @flags:		Connection flags representing internal attributes
+ * @hash_bucket:	Bucket index in connection lookup hash table
+ * @retrans:		Number of retransmissions occurred due to ACK_TIMEOUT
+ * @ws_from_tap:	Window scaling factor advertised from tap/guest
+ * @ws_to_tap:		Window scaling factor advertised to tap/guest
+ * @sndbuf:		Sending buffer in kernel, rounded to 2 ^ SNDBUF_BITS
+ * @seq_dup_ack_approx:	Last duplicate ACK number sent to tap
+ * @a.a6:		IPv6 remote address, can be IPv4-mapped
+ * @a.a4.zero:		Zero prefix for IPv4-mapped, see RFC 6890, Table 20
+ * @a.a4.one:		Ones prefix for IPv4-mapped
+ * @a.a4.a:		IPv4 address
+ * @tap_port:		Guest-facing tap port
+ * @sock_port:		Remote, socket-facing port
+ * @wnd_from_tap:	Last window size from tap, unscaled (as received)
+ * @wnd_to_tap:		Sending window advertised to tap, unscaled (as sent)
+ * @seq_to_tap:		Next sequence for packets to tap
+ * @seq_ack_from_tap:	Last ACK number received from tap
+ * @seq_from_tap:	Next sequence for packets from tap (not actually sent)
+ * @seq_ack_to_tap:	Last ACK number sent to tap
+ * @seq_init_from_tap:	Initial sequence number from tap
+ */
+struct tcp_tap_conn {
+	int	 	next_index	:TCP_CONN_INDEX_BITS + 2;
+
+#define TCP_RETRANS_BITS		3
+	unsigned int	retrans		:TCP_RETRANS_BITS;
+#define TCP_MAX_RETRANS			((1U << TCP_RETRANS_BITS) - 1)
+
+#define TCP_WS_BITS			4	/* RFC 7323 */
+#define TCP_WS_MAX			14
+	unsigned int	ws_from_tap	:TCP_WS_BITS;
+	unsigned int	ws_to_tap	:TCP_WS_BITS;
+
+
+	int		sock		:SOCKET_REF_BITS;
+
+	uint8_t		events;
+#define CLOSED			0
+#define SOCK_ACCEPTED		BIT(0)	/* implies SYN sent to tap */
+#define TAP_SYN_RCVD		BIT(1)	/* implies socket connecting */
+#define  TAP_SYN_ACK_SENT	BIT( 3)	/* implies socket connected */
+#define ESTABLISHED		BIT(2)
+#define  SOCK_FIN_RCVD		BIT( 3)
+#define  SOCK_FIN_SENT		BIT( 4)
+#define  TAP_FIN_RCVD		BIT( 5)
+#define  TAP_FIN_SENT		BIT( 6)
+#define  TAP_FIN_ACKED		BIT( 7)
+
+#define	CONN_STATE_BITS		/* Setting these clears other flags */	\
+	(SOCK_ACCEPTED | TAP_SYN_RCVD | ESTABLISHED)
+
+
+	int		timer		:SOCKET_REF_BITS;
+
+	uint8_t		flags;
+#define STALLED			BIT(0)
+#define LOCAL			BIT(1)
+#define WND_CLAMPED		BIT(2)
+#define IN_EPOLL		BIT(3)
+#define ACTIVE_CLOSE		BIT(4)
+#define ACK_TO_TAP_DUE		BIT(5)
+#define ACK_FROM_TAP_DUE	BIT(6)
+
+
+	unsigned int	hash_bucket	:TCP_HASH_BUCKET_BITS;
+
+#define TCP_MSS_BITS			14
+	unsigned int	tap_mss		:TCP_MSS_BITS;
+#define MSS_SET(conn, mss)	(conn->tap_mss = (mss >> (16 - TCP_MSS_BITS)))
+#define MSS_GET(conn)		(conn->tap_mss << (16 - TCP_MSS_BITS))
+
+
+#define SNDBUF_BITS		24
+	unsigned int	sndbuf		:SNDBUF_BITS;
+#define SNDBUF_SET(conn, bytes)	(conn->sndbuf = ((bytes) >> (32 - SNDBUF_BITS)))
+#define SNDBUF_GET(conn)	(conn->sndbuf << (32 - SNDBUF_BITS))
+
+	uint8_t		seq_dup_ack_approx;
+
+
+	union {
+		struct in6_addr a6;
+		struct {
+			uint8_t zero[10];
+			uint8_t one[2];
+			struct in_addr a;
+		} a4;
+	} a;
+
+	in_port_t	tap_port;
+	in_port_t	sock_port;
+
+	uint16_t	wnd_from_tap;
+	uint16_t	wnd_to_tap;
+
+	uint32_t	seq_to_tap;
+	uint32_t	seq_ack_from_tap;
+	uint32_t	seq_from_tap;
+	uint32_t	seq_ack_to_tap;
+	uint32_t	seq_init_from_tap;
+};
+
+/**
+ * struct tcp_splice_conn - Descriptor for a spliced TCP connection
+ * @a:			File descriptor number of socket for accepted connection
+ * @pipe_a_b:		Pipe ends for splice() from @a to @b
+ * @b:			File descriptor number of peer connected socket
+ * @pipe_b_a:		Pipe ends for splice() from @b to @a
+ * @events:		Events observed/actions performed on connection
+ * @flags:		Connection flags (attributes, not events)
+ * @a_read:		Bytes read from @a (not fully written to @b in one shot)
+ * @a_written:		Bytes written to @a (not fully written from one @b read)
+ * @b_read:		Bytes read from @b (not fully written to @a in one shot)
+ * @b_written:		Bytes written to @b (not fully written from one @a read)
+*/
+struct tcp_splice_conn {
+	int a;
+	int pipe_a_b[2];
+	int b;
+	int pipe_b_a[2];
+
+	uint8_t events;
+#define SPLICE_CLOSED			0
+#define SPLICE_CONNECT			BIT(0)
+#define SPLICE_ESTABLISHED		BIT(1)
+#define A_OUT_WAIT			BIT(2)
+#define B_OUT_WAIT			BIT(3)
+#define A_FIN_RCVD			BIT(4)
+#define B_FIN_RCVD			BIT(5)
+#define A_FIN_SENT			BIT(6)
+#define B_FIN_SENT			BIT(7)
+
+	uint8_t flags;
+#define SPLICE_V6			BIT(0)
+#define SPLICE_IN_EPOLL			BIT(1)
+#define RCVLOWAT_SET_A			BIT(2)
+#define RCVLOWAT_SET_B			BIT(3)
+#define RCVLOWAT_ACT_A			BIT(4)
+#define RCVLOWAT_ACT_B			BIT(5)
+#define CLOSING				BIT(6)
+
+	uint32_t a_read;
+	uint32_t a_written;
+	uint32_t b_read;
+	uint32_t b_written;
+};
+
+#endif /* TCP_CONN_H */