Add inet_sockaddr2str() to wrap inet_ntop(3)

Signed-off-by: Alejandro Colomar <alx@kernel.org>

lib/prototypes.h

@@ -21,6 +21,7 @@
 
 #include <config.h>
 
+#include <sys/socket.h>
 #include <sys/stat.h>
 #include <utmp.h>
 #include <sys/types.h>
@@ -193,6 +194,9 @@ extern bool gr_append_member (struct group *grp, char *member);
 /* hushed.c */
 extern bool hushed (const char *username);
 
+/* inet_sockaddr2str.c */
+extern const char *inet_sockaddr2str(const struct sockaddr *sa);
+
 /* audit_help.c */
 #ifdef WITH_AUDIT
 extern int audit_fd;

libmisc/Makefile.am

@@ -38,6 +38,7 @@ libmisc_la_SOURCES = \
 	hushed.c \
 	idmapping.h \
 	idmapping.c \
+	inet_sockaddr2str.c \
 	isexpired.c \
 	limits.c \
 	list.c log.c \

libmisc/inet_sockaddr2str.c

@@ -0,0 +1,78 @@
+/*
+ * SPDX-FileCopyrightText: 2022, Alejandro Colomar <alx@kernel.org>
+ *
+ * SPDX-License-Identifier:  BSD-3-Clause
+ */
+
+#include <config.h>
+
+#include <arpa/inet.h>
+#include <errno.h>
+#include <netinet/in.h>
+#include <sys/param.h>
+#include <sys/socket.h>
+
+#ident "$Id$"
+
+#include "defines.h"
+#include "prototypes.h"
+
+
+#if !defined(INET_ADDRSTRLENMAX)
+#define INET_ADDRSTRLENMAX  MAX(INET_ADDRSTRLEN, INET6_ADDRSTRLEN)
+#endif
+
+
+/*
+ * SYNOPSIS
+ *	const char *inet_sockaddr2str(const struct sockaddr *sa);
+ *
+ * DESCRIPTION
+ *	This function is similar to inet_ntop(3).  It transforms an address
+ *	in 'struct in_addr' or 'struct in6_addr' form into a human-readable
+ *	string.
+ *
+ *	It receives a sockaddr structure, which is simpler to pass after
+ *	receiving it from getaddrinfo(3).  However, this function is not
+ *	reentrant, and like inet_ntoa(3), it uses an internal buffer, for
+ *	simplicity; anyway we're not in a multithreaded program, and it
+ *	doesn't contain any sensitive data, so it's fine to use static
+ *	storage here.
+ *
+ * RETURN VALUE
+ *	This function returns a pointer to a statically allocated buffer,
+ *	which subsequent calls will overwrite.
+ *
+ *	On error, it returns NULL.
+ *
+ * ERRORS
+ *	EAFNOSUPPORT
+ *		The address family in sa->sa_family is not AF_INET or AF_INET6.
+ *
+ * CAVEATS
+ *	This function is not reentrant.
+ */
+
+
+const char *
+inet_sockaddr2str(const struct sockaddr *sa)
+{
+	struct sockaddr_in   *sin;
+	struct sockaddr_in6  *sin6;
+
+	static char          buf[INET_ADDRSTRLENMAX];
+
+	switch (sa->sa_family) {
+	case AF_INET:
+		sin = (struct sockaddr_in *) sa;
+		inet_ntop(AF_INET, &sin->sin_addr, buf, NITEMS(buf));
+		return buf;
+	case AF_INET6:
+		sin6 = (struct sockaddr_in6 *) sa;
+		inet_ntop(AF_INET6, &sin6->sin6_addr, buf, NITEMS(buf));
+		return buf;
+	default:
+		errno = EAFNOSUPPORT;
+		return NULL;
+	}
+}