util: Add helper to return name of address family

We have a few places where we want to include the name of the internet
protocol version (IPv4 or IPv6) in a message, which we handle with an
open-coded ?: expression.

This seems like something that might be more widely useful, so make a
trivial helper to return the correct string based on the address family.

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

2 files changed, 21 insertions, 3 deletions

diff --git a/netlink.c b/netlink.c
index 59e9e33..0549237 100644
--- a/netlink.c
+++ b/netlink.c
@@ -309,7 +309,7 @@ unsigned int nl_get_ext_if(int s, sa_family_t af)
 	if (defifi) {
 		if (ndef > 1)
 			info("Multiple default %s routes, picked first",
-			     af == AF_INET ? "IPv4" : "IPv6");
+			     af_name(af));
 		return defifi;
 	}
 
@@ -318,11 +318,11 @@ unsigned int nl_get_ext_if(int s, sa_family_t af)
 			return anyifi;
 
 		info("Multiple interfaces with %s routes, use -i to select one",
-		     af == AF_INET ? "IPv4" : "IPv6");
+		     af_name(af));
 	}
 
 	if (!nany)
-		info("No interfaces with %s routes", af == AF_INET ? "IPv4" : "IPv6");
+		info("No interfaces with %s routes", af_name(af));
 
 	return 0;
 }
diff --git a/util.h b/util.h
index 48f3560..7c261d7 100644
--- a/util.h
+++ b/util.h
@@ -157,6 +157,24 @@ int write_file(const char *path, const char *buf);
 int write_remainder(int fd, const struct iovec *iov, int iovcnt, size_t skip);
 
 /**
+ * af_name() - Return name of an address family
+ * @af:		Address/protocol family (AF_INET or AF_INET6)
+ *
+ * Returns: Name of the protocol family as a string
+ */
+static inline const char *af_name(sa_family_t af)
+{
+	switch (af) {
+	case AF_INET:
+		return "IPv4";
+	case AF_INET6:
+		return "IPv6";
+	default:
+		return "<unknown address family>";
+	}
+}
+
+/**
  * mod_sub() - Modular arithmetic subtraction
  * @a:		Minued, unsigned value < @m
  * @b:		Subtrahend, unsigned value < @m