dhcp: add generic DUID infrastructure

Add infrastructure for generating DUID-LLT from a given device MAC and
passing it around to the DHCP client implementations.

Thanks to Mathieu Trudel-Lapierre for bug fixes in the
unescaping code, which were merged into this commit.

src/dhcp-manager/nm-dhcp-dhclient-utils.c

@@ -22,6 +22,7 @@
 #include <glib.h>
 #include <glib/gi18n.h>
 #include <string.h>
+#include <ctype.h>
 
 #include "nm-dhcp-dhclient-utils.h"
 
@@ -255,3 +256,75 @@ nm_dhcp_dhclient_create_config (const char *interface,
 	return g_string_free (new_contents, FALSE);
 }
 
+/* Roughly follow what dhclient's quotify_buf() and pretty_escape() functions do */
+char *
+nm_dhcp_dhclient_escape_duid (const GByteArray *duid)
+{
+	char *escaped;
+	const guint8 *s = duid->data;
+	char *d;
+
+	d = escaped = g_malloc0 ((duid->len * 4) + 1);
+	while (s < (duid->data + duid->len)) {
+		if (!g_ascii_isprint (*s)) {
+			*d++ = '\\';
+			*d++ = '0' + ((*s >> 6) & 0x7);
+			*d++ = '0' + ((*s >> 3) & 0x7);
+			*d++ = '0' + (*s++ & 0x7);
+		} else if (*s == '"' || *s == '\'' || *s == '$' ||
+		           *s == '`' || *s == '\\' || *s == '|' ||
+		           *s == '&') {
+			*d++ = '\\';
+			*d++ = *s++;
+		} else
+			*d++ = *s++;
+	}
+	return escaped;
+}
+
+static inline gboolean
+isoctal (const guint8 *p)
+{
+	return (   p[0] >= '0' && p[0] <= '3'
+	        && p[1] >= '0' && p[1] <= '7'
+	        && p[2] >= '0' && p[2] <= '7');
+}
+
+GByteArray *
+nm_dhcp_dhclient_unescape_duid (const char *duid)
+{
+	GByteArray *unescaped;
+	const guint8 *p = (const guint8 *) duid;
+	guint i, len;
+	guint8 octal;
+
+	len = strlen (duid);
+	unescaped = g_byte_array_sized_new (len);
+	for (i = 0; i < len; i++) {
+		if (p[i] == '\\') {
+			i++;
+			if (isdigit (p[i])) {
+				/* Octal escape sequence */
+				if (i + 2 >= len || !isoctal (p + i))
+					goto error;
+				octal = ((p[i] - '0') << 6) + ((p[i + 1] - '0') << 3) + (p[i + 2] - '0');
+				g_byte_array_append (unescaped, &octal, 1);
+				i += 2;
+			} else {
+				/* One of ", ', $, `, \, |, or & */
+				g_warn_if_fail (p[i] == '"' || p[i] == '\'' || p[i] == '$' ||
+				                p[i] == '`' || p[i] == '\\' || p[i] == '|' ||
+				                p[i] == '&');
+				g_byte_array_append (unescaped, &p[i], 1);
+			}
+		} else
+			g_byte_array_append (unescaped, &p[i], 1);
+	}
+
+	return unescaped;
+
+error:
+	g_byte_array_free (unescaped, TRUE);
+	return NULL;
+}
+