--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libutil/sockinit.c	Sat Jun 25 18:33:29 2022 -0800
@@ -0,0 +1,40 @@
+/*
+ * This library module implements a function that helps initialize
+ * sockaddr for bind or connect operations on UNIX domain sockets.
+ *
+ * Back when I programmed under 4.3BSD UNIX, this operation was simple
+ * and straightforward - but under "modern" Unixes, it appears to be
+ * a complex affair, given the messy code (originally copied from
+ * Osmocom) that appears in FreeCalypso host tools for the rvinterf
+ * local socket interface.  Hence I am factoring that mess out into
+ * its own library function this time around.
+ */
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <string.h>
+#include <strings.h>
+
+void
+fill_sockaddr_un(pathname, sunp, lenp)
+	char *pathname;
+	struct sockaddr_un *sunp;
+	unsigned *lenp;
+{
+	/* local socket binding voodoo copied from osmocon */
+	sunp->sun_family = AF_UNIX;
+	strncpy(sunp->sun_path, pathname, sizeof(sunp->sun_path));
+	sunp->sun_path[sizeof(sunp->sun_path) - 1] = '\0';
+	/* we use the same magic that X11 uses in Xtranssock.c for
+	 * calculating the proper length of the sockaddr */
+#if defined(BSD44SOCKETS) || defined(__UNIXWARE__)
+	sunp->sun_len = strlen(sunp->sun_path);
+#endif
+#if defined(BSD44SOCKETS) || defined(SUN_LEN)
+	*lenp = SUN_LEN(sunp);
+#else
+	*lenp = strlen(sunp->sun_path) +
+		offsetof(struct sockaddr_un, sun_path) + 1;
+#endif
+}