flow, tcp: Generalise connection types

Currently TCP connections use a 1-bit selector, 'spliced', to determine the
rest of the contents of the structure.  We want to generalise the TCP
connection table to other types of flows in other protocols.  Make a start
on this by replacing the tcp_conn_common structure with a new flow_common
structure with an enum rather than a simple boolean indicating the type of
flow.

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

6 files changed, 112 insertions, 40 deletions

diff --git a/Makefile b/Makefile
index 6c53695..e2970e3 100644
--- a/Makefile
+++ b/Makefile
@@ -44,15 +44,15 @@ FLAGS += -DARCH=\"$(TARGET_ARCH)\"
 FLAGS += -DVERSION=\"$(VERSION)\"
 FLAGS += -DDUAL_STACK_SOCKETS=$(DUAL_STACK_SOCKETS)
 
-PASST_SRCS = arch.c arp.c checksum.c conf.c dhcp.c dhcpv6.c icmp.c igmp.c \
-	isolation.c lineread.c log.c mld.c ndp.c netlink.c packet.c passt.c \
-	pasta.c pcap.c port_fwd.c tap.c tcp.c tcp_splice.c udp.c util.c
+PASST_SRCS = arch.c arp.c checksum.c conf.c dhcp.c dhcpv6.c flow.c icmp.c \
+	igmp.c isolation.c lineread.c log.c mld.c ndp.c netlink.c packet.c \
+	passt.c pasta.c pcap.c port_fwd.c tap.c tcp.c tcp_splice.c udp.c util.c
 QRAP_SRCS = qrap.c
 SRCS = $(PASST_SRCS) $(QRAP_SRCS)
 
 MANPAGES = passt.1 pasta.1 qrap.1
 
-PASST_HEADERS = arch.h arp.h checksum.h conf.h dhcp.h dhcpv6.h icmp.h \
+PASST_HEADERS = arch.h arp.h checksum.h conf.h dhcp.h dhcpv6.h flow.h icmp.h \
 	inany.h isolation.h lineread.h log.h ndp.h netlink.h packet.h passt.h \
 	pasta.h pcap.h pif.h port_fwd.h siphash.h tap.h tcp.h tcp_conn.h \
 	tcp_splice.h udp.h util.h
diff --git a/flow.c b/flow.c
new file mode 100644
index 0000000..b71358a
--- /dev/null
+++ b/flow.c
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later
+ * Copyright Red Hat
+ * Author: David Gibson <david@gibson.dropbear.id.au>
+ *
+ * Tracking for logical "flows" of packets.
+ */
+
+#include <stdint.h>
+
+#include "flow.h"
+
+const char *flow_type_str[] = {
+	[FLOW_TYPE_NONE]	= "<none>",
+	[FLOW_TCP]		= "TCP connection",
+	[FLOW_TCP_SPLICE]	= "TCP connection (spliced)",
+};
+static_assert(ARRAY_SIZE(flow_type_str) == FLOW_NUM_TYPES,
+	      "flow_type_str[] doesn't match enum flow_type");
diff --git a/flow.h b/flow.h
new file mode 100644
index 0000000..351837d
--- /dev/null
+++ b/flow.h
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later
+ * Copyright Red Hat
+ * Author: David Gibson <david@gibson.dropbear.id.au>
+ *
+ * Tracking for logical "flows" of packets.
+ */
+#ifndef FLOW_H
+#define FLOW_H
+
+/**
+ * enum flow_type - Different types of packet flows we track
+ */
+enum flow_type {
+	/* Represents an invalid or unused flow */
+	FLOW_TYPE_NONE = 0,
+	/* A TCP connection between a socket and tap interface */
+	FLOW_TCP,
+	/* A TCP connection between a host socket and ns socket */
+	FLOW_TCP_SPLICE,
+
+	FLOW_NUM_TYPES,
+};
+
+extern const char *flow_type_str[];
+#define FLOW_TYPE(f)							\
+        ((f)->type < FLOW_NUM_TYPES ? flow_type_str[(f)->type] : "?")
+
+/**
+ * struct flow_common - Common fields for packet flows
+ * @type:	Type of packet flow
+ */
+struct flow_common {
+	uint8_t		type;
+};
+
+#endif /* FLOW_H */
diff --git a/tcp.c b/tcp.c
index e683dd9..8139dac 100644
--- a/tcp.c
+++ b/tcp.c
@@ -299,6 +299,7 @@
 #include "tcp_splice.h"
 #include "log.h"
 #include "inany.h"
+#include "flow.h"
 
 #include "tcp_conn.h"
 
@@ -584,7 +585,7 @@ static inline struct tcp_tap_conn *conn_at_idx(int idx)
 {
 	if ((idx < 0) || (idx >= TCP_MAX_CONNS))
 		return NULL;
-	ASSERT(!(CONN(idx)->c.spliced));
+	ASSERT(CONN(idx)->f.type == FLOW_TCP);
 	return CONN(idx);
 }
 
@@ -1319,14 +1320,21 @@ void tcp_table_compact(struct ctx *c, union tcp_conn *hole)
 	from = tc + c->tcp.conn_count;
 	memcpy(hole, from, sizeof(*hole));
 
-	if (from->c.spliced)
-		tcp_splice_conn_update(c, &hole->splice);
-	else
+	switch (from->f.type) {
+	case FLOW_TCP:
 		tcp_tap_conn_update(c, &from->tap, &hole->tap);
+		break;
+	case FLOW_TCP_SPLICE:
+		tcp_splice_conn_update(c, &hole->splice);
+		break;
+	default:
+		die("Unexpected %s in tcp_table_compact()",
+		    FLOW_TYPE(&from->f));
+	}
 
-	debug("TCP: table compaction (spliced=%d): old index %li, new index %li, "
+	debug("TCP: table compaction (%s): old index %li, new index %li, "
 	      "from: %p, to: %p",
-	      from->c.spliced, CONN_IDX(from), CONN_IDX(hole),
+	      FLOW_TYPE(&from->f), CONN_IDX(from), CONN_IDX(hole),
 	      (void *)from, (void *)hole);
 
 	memset(from, 0, sizeof(*from));
@@ -1402,12 +1410,18 @@ void tcp_defer_handler(struct ctx *c)
 	tcp_l2_data_buf_flush(c);
 
 	for (conn = tc + c->tcp.conn_count - 1; conn >= tc; conn--) {
-		if (conn->c.spliced) {
-			if (conn->splice.flags & CLOSING)
-				tcp_splice_destroy(c, conn);
-		} else {
+		switch (conn->f.type) {
+		case FLOW_TCP:
 			if (conn->tap.events == CLOSED)
 				tcp_conn_destroy(c, conn);
+			break;
+		case FLOW_TCP_SPLICE:
+			if (conn->splice.flags & CLOSING)
+				tcp_splice_destroy(c, conn);
+			break;
+		default:
+			die("Unexpected %s in tcp_defer_handler()",
+			    FLOW_TYPE(&conn->f));
 		}
 	}
 }
@@ -2016,7 +2030,7 @@ static void tcp_conn_from_tap(struct ctx *c,
 	}
 
 	conn = CONN(c->tcp.conn_count++);
-	conn->c.spliced = false;
+	conn->f.type = FLOW_TCP;
 	conn->sock = s;
 	conn->timer = -1;
 	conn_event(c, conn, TAP_SYN_RCVD);
@@ -2726,7 +2740,7 @@ static void tcp_tap_conn_from_sock(struct ctx *c,
 				   const struct sockaddr *sa,
 				   const struct timespec *now)
 {
-	conn->c.spliced = false;
+	conn->f.type = FLOW_TCP;
 	conn->sock = s;
 	conn->timer = -1;
 	conn->ws_to_tap = conn->ws_from_tap = 0;
@@ -2909,10 +2923,17 @@ void tcp_sock_handler(struct ctx *c, union epoll_ref ref, uint32_t events)
 {
 	union tcp_conn *conn = tc + ref.tcp.index;
 
-	if (conn->c.spliced)
-		tcp_splice_sock_handler(c, &conn->splice, ref.fd, events);
-	else
+	switch (conn->f.type) {
+	case FLOW_TCP:
 		tcp_tap_sock_handler(c, &conn->tap, events);
+		break;
+	case FLOW_TCP_SPLICE:
+		tcp_splice_sock_handler(c, &conn->splice, ref.fd, events);
+		break;
+	default:
+		die("Unexpected %s in tcp_sock_handler_compact()",
+		    FLOW_TYPE(&conn->f));
+	}
 }
 
 /**
@@ -3244,11 +3265,17 @@ void tcp_timer(struct ctx *c, const struct timespec *ts)
 	}
 
 	for (conn = tc + c->tcp.conn_count - 1; conn >= tc; conn--) {
-		if (conn->c.spliced) {
-			tcp_splice_timer(c, conn);
-		} else {
+		switch (conn->f.type) {
+		case FLOW_TCP:
 			if (conn->tap.events == CLOSED)
 				tcp_conn_destroy(c, conn);
+			break;
+		case FLOW_TCP_SPLICE:
+			tcp_splice_timer(c, conn);
+			break;
+		default:
+			die("Unexpected %s in tcp_timer()",
+			    FLOW_TYPE(&conn->f));
 		}
 	}
 
diff --git a/tcp_conn.h b/tcp_conn.h
index 0c6a35b..136f8da 100644
--- a/tcp_conn.h
+++ b/tcp_conn.h
@@ -10,18 +10,8 @@
 #define TCP_CONN_H
 
 /**
- * struct tcp_conn_common - Common fields for spliced and non-spliced
- * @spliced:		Is this a spliced connection?
- */
-struct tcp_conn_common {
-	bool spliced	:1;
-};
-
-extern const char *tcp_common_flag_str[];
-
-/**
  * struct tcp_tap_conn - Descriptor for a TCP connection (not spliced)
- * @c:			Fields common with tcp_splice_conn
+ * @f:			Generic flow information
  * @in_epoll:		Is the connection in the epoll set?
  * @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
@@ -46,8 +36,8 @@ extern const char *tcp_common_flag_str[];
  * @seq_init_from_tap:	Initial sequence number from tap
  */
 struct tcp_tap_conn {
-	/* Must be first element to match tcp_splice_conn */
-	struct tcp_conn_common c;
+	/* Must be first element */
+	struct flow_common f;
 
 	bool		in_epoll	:1;
 	int	 	next_index	:TCP_CONN_INDEX_BITS + 2;
@@ -121,7 +111,7 @@ struct tcp_tap_conn {
 #define SIDES			2
 /**
  * struct tcp_splice_conn - Descriptor for a spliced TCP connection
- * @c:			Fields common with tcp_tap_conn
+ * @f:			Generic flow information
  * @in_epoll:		Is the connection in the epoll set?
  * @s:			File descriptor for sockets
  * @pipe:		File descriptors for pipes
@@ -131,8 +121,8 @@ struct tcp_tap_conn {
  * @written:		Bytes written (not fully written from one other side read)
 */
 struct tcp_splice_conn {
-	/* Must be first element to match tcp_tap_conn */
-	struct tcp_conn_common c;
+	/* Must be first element */
+	struct flow_common f;
 
 	bool in_epoll	:1;
 	int s[SIDES];
@@ -168,7 +158,7 @@ struct tcp_splice_conn {
  * @splice:		Fields specific to spliced connections
 */
 union tcp_conn {
-	struct tcp_conn_common c;
+	struct flow_common f;
 	struct tcp_tap_conn tap;
 	struct tcp_splice_conn splice;
 };
diff --git a/tcp_splice.c b/tcp_splice.c
index 0a23584..c55c491 100644
--- a/tcp_splice.c
+++ b/tcp_splice.c
@@ -54,6 +54,7 @@
 #include "tcp_splice.h"
 #include "siphash.h"
 #include "inany.h"
+#include "flow.h"
 
 #include "tcp_conn.h"
 
@@ -476,7 +477,7 @@ bool tcp_splice_conn_from_sock(const struct ctx *c,
 	if (setsockopt(s, SOL_TCP, TCP_QUICKACK, &((int){ 1 }), sizeof(int)))
 		trace("TCP (spliced): failed to set TCP_QUICKACK on %i", s);
 
-	conn->c.spliced = true;
+	conn->f.type = FLOW_TCP_SPLICE;
 	conn->s[0] = s;
 
 	if (tcp_splice_new(c, conn, ref.port, ref.pif))