[PATCH v2 14/15] fwd_rule: Move forwarding rule text formatting to common code

[David Gibson <david@gibson.dropbear.id.au>]

Move the logic for formatting forwarding rules into strings from
fwd_rules_print() into fwd_rule.c where it can be shared with pesto.
We also make the function explicitly construct a string, rather than
directly printing with info(), for greater flexibility.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 Makefile   | 11 ++++----
 fwd.c      | 40 +++---------------------------
 fwd_rule.c | 73 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 fwd_rule.h | 11 ++++++++
 4 files changed, 94 insertions(+), 41 deletions(-)
 create mode 100644 fwd_rule.c

diff --git a/Makefile b/Makefile
index bc325482..44c396e7 100644
--- a/Makefile
+++ b/Makefile
@@ -38,13 +38,14 @@ FLAGS += -DVERSION=\"$(VERSION)\"
 FLAGS += -DDUAL_STACK_SOCKETS=$(DUAL_STACK_SOCKETS)
 
 PASST_SRCS = arch.c arp.c checksum.c conf.c dhcp.c dhcpv6.c epoll_ctl.c \
-	flow.c fwd.c icmp.c igmp.c inany.c iov.c ip.c isolation.c lineread.c \
-	log.c mld.c ndp.c netlink.c migrate.c packet.c passt.c pasta.c pcap.c \
-	pif.c repair.c serialise.c tap.c tcp.c tcp_buf.c tcp_splice.c tcp_vu.c \
-	udp.c udp_flow.c udp_vu.c util.c vhost_user.c virtio.c vu_common.c
+	flow.c fwd.c fwd_rule.c icmp.c igmp.c inany.c iov.c ip.c isolation.c \
+	lineread.c log.c mld.c ndp.c netlink.c migrate.c packet.c passt.c \
+	pasta.c pcap.c pif.c repair.c serialise.c tap.c tcp.c tcp_buf.c \
+	tcp_splice.c tcp_vu.c udp.c udp_flow.c udp_vu.c util.c vhost_user.c \
+	virtio.c vu_common.c
 QRAP_SRCS = qrap.c
 PASST_REPAIR_SRCS = passt-repair.c
-PESTO_SRCS = pesto.c inany.c ip.c serialise.c
+PESTO_SRCS = pesto.c fwd_rule.c inany.c ip.c serialise.c
 SRCS = $(PASST_SRCS) $(QRAP_SRCS) $(PASST_REPAIR_SRCS) $(PESTO_SRCS)
 
 MANPAGES = passt.1 pasta.1 pesto.1 qrap.1 passt-repair.1
diff --git a/fwd.c b/fwd.c
index f157eeb6..72028e70 100644
--- a/fwd.c
+++ b/fwd.c
@@ -304,20 +304,6 @@ parse_err:
 	warn("Unable to parse %s", PORT_RANGE_SYSCTL);
 }
 
-/**
- * fwd_rule_addr() - Return match address for a rule
- * @rule:	Forwarding rule
- *
- * Return: matching address for rule, NULL if it matches all addresses
- */
-static const union inany_addr *fwd_rule_addr(const struct fwd_rule *rule)
-{
-	if (rule->flags & FWD_DUAL_STACK_ANY)
-		return NULL;
-
-	return &rule->addr;
-}
-
 /**
  * fwd_port_is_ephemeral() - Is port number ephemeral?
  * @port:	Port number
@@ -495,28 +481,10 @@ void fwd_rules_print(const struct fwd_table *fwd)
 	unsigned i;
 
 	for (i = 0; i < fwd->count; i++) {
-		const struct fwd_rule *rule = &fwd->rules[i].rule;
-		const char *percent = *rule->ifname ? "%" : "";
-		const char *weak = "", *scan = "";
-		char addr[INANY_ADDRSTRLEN];
-
-		inany_ntop(fwd_rule_addr(rule), addr, sizeof(addr));
-		if (rule->flags & FWD_WEAK)
-			weak = " (best effort)";
-		if (rule->flags & FWD_SCAN)
-			scan = " (auto-scan)";
-
-		if (rule->first == rule->last) {
-			info("    %s [%s]%s%s:%hu  =>  %hu %s%s",
-			     ipproto_name(rule->proto), addr, percent,
-			     rule->ifname, rule->first, rule->to, weak, scan);
-		} else {
-			info("    %s [%s]%s%s:%hu-%hu  =>  %hu-%hu %s%s",
-			     ipproto_name(rule->proto), addr, percent,
-			     rule->ifname, rule->first, rule->last,
-			     rule->to, rule->last - rule->first + rule->to,
-			     weak, scan);
-		}
+		char rulestr[FWD_RULE_STRLEN];
+
+		info("    %s", fwd_rule_ntop(&fwd->rules[i].rule,
+					     rulestr, sizeof(rulestr)));
 	}
 }
 
diff --git a/fwd_rule.c b/fwd_rule.c
new file mode 100644
index 00000000..dfbdf683
--- /dev/null
+++ b/fwd_rule.c
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+/* PASST - Plug A Simple Socket Transport
+ *  for qemu/UNIX domain socket mode
+ *
+ * PASTA - Pack A Subtle Tap Abstraction
+ *  for network namespace/tap device mode
+ *
+ * PESTO - Programmable Extensible Socket Translation Orchestrator
+ *  front-end for passt(1) and pasta(1) forwarding configuration
+ *
+ * fwd_rule.c - Helpers for working with forwarding rule specifications
+ *
+ * Copyright Red Hat
+ * Author: David Gibson <david@gibson.dropbear.id.au>
+ */
+
+#include <stdio.h>
+
+#include "fwd_rule.h"
+
+/**
+ * fwd_rule_addr() - Return match address for a rule
+ * @rule:	Forwarding rule
+ *
+ * Return: matching address for rule, NULL if it matches all addresses
+ */
+const union inany_addr *fwd_rule_addr(const struct fwd_rule *rule)
+{
+	if (rule->flags & FWD_DUAL_STACK_ANY)
+		return NULL;
+
+	return &rule->addr;
+}
+
+/**
+ * fwd_rule_ntop() - Format forwarding rule as a string
+ * @rule:	Rule to format
+ * @dst:	Buffer to store output (should have FWD_RULE_STRLEN bytes)
+ * @size:	Size of @dst
+ */
+const char *fwd_rule_ntop(const struct fwd_rule *rule, char *dst, size_t size)
+{
+	const char *percent = *rule->ifname ? "%" : "";
+	const char *weak = "", *scan = "";
+	char addr[INANY_ADDRSTRLEN];
+	int len;
+
+	inany_ntop(fwd_rule_addr(rule), addr, sizeof(addr));
+	if (rule->flags & FWD_WEAK)
+		weak = " (best effort)";
+	if (rule->flags & FWD_SCAN)
+		scan = " (auto-scan)";
+
+	if (rule->first == rule->last) {
+		len = snprintf(dst, size,
+			       "%s [%s]%s%s:%hu  =>  %hu %s%s",
+			       ipproto_name(rule->proto), addr, percent,
+			       rule->ifname, rule->first, rule->to, weak, scan);
+	} else {
+		in_port_t tolast = rule->last - rule->first + rule->to;
+		len = snprintf(dst, size,
+			       "%s [%s]%s%s:%hu-%hu  =>  %hu-%hu %s%s",
+			       ipproto_name(rule->proto), addr, percent,
+			       rule->ifname, rule->first, rule->last,
+			       rule->to, tolast, weak, scan);
+	}
+
+	if (len < 0 || (size_t)len >= size)
+		return NULL;
+
+	return dst;
+}
diff --git a/fwd_rule.h b/fwd_rule.h
index 84ec5cbe..59db0e95 100644
--- a/fwd_rule.h
+++ b/fwd_rule.h
@@ -42,4 +42,15 @@ struct fwd_rule {
 	uint8_t flags;
 };
 
+const union inany_addr *fwd_rule_addr(const struct fwd_rule *rule);
+
+#define FWD_RULE_STRLEN					    \
+	(IPPROTO_STRLEN - 1				    \
+	 + INANY_ADDRSTRLEN - 1				    \
+	 + IFNAMSIZ - 1					    \
+	 + sizeof(" (best effort)") - 1			    \
+	 + sizeof(" (auto-scan)") - 1			    \
+	 + 15)
+const char *fwd_rule_ntop(const struct fwd_rule *rule, char *dst, size_t size);
+
 #endif /* FWD_RULE_H */
-- 
2.53.0