[ipv4] Rewrite inet_aton()

The implementation of inet_aton() has an unknown provenance.  Rewrite
this code to avoid potential licensing uncertainty.

Also move the code from core/misc.c to its logical home in net/ipv4.c,
and add a few extra test cases.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/core/misc.c

 #include <ipxe/in.h>
 #include <ipxe/timer.h>
 
-/**************************************************************************
-INET_ATON - Convert an ascii x.x.x.x to binary form
-**************************************************************************/
-int inet_aton ( const char *cp, struct in_addr *inp ) {
-	const char *p = cp;
-	const char *digits_start;
-	unsigned long ip = 0;
-	unsigned long val;
-	int j;
-	for(j = 0; j <= 3; j++) {
-		digits_start = p;
-		val = strtoul(p, ( char ** ) &p, 10);
-		if ((p == digits_start) || (val > 255)) return 0;
-		if ( ( j < 3 ) && ( *(p++) != '.' ) ) return 0;
-		ip = (ip << 8) | val;
-	}
-	if ( *p == '\0' ) {
-		inp->s_addr = htonl(ip);
-		return 1;
-	}
-	return 0;
-}
-
 unsigned int strtoul_charval ( unsigned int charval ) {
 
 	if ( charval >= 'a' ) {

src/net/ipv4.c

 	return -ENOENT;
 }
 
+/**
+ * Parse IPv4 address
+ *
+ * @v string		IPv4 address string
+ * @ret in		IPv4 address to fill in
+ * @ret ok		IPv4 address is valid
+ *
+ * Note that this function returns nonzero iff the address is valid,
+ * to match the standard BSD API function of the same name.  Unlike
+ * most other iPXE functions, a zero therefore indicates failure.
+ */
+int inet_aton ( const char *string, struct in_addr *in ) {
+	const char *separator = "...";
+	uint8_t *byte = ( ( uint8_t * ) in );
+	char *endp;
+	unsigned long value;
+
+	while ( 1 ) {
+		value = strtoul ( string, &endp, 0 );
+		if ( string == endp )
+			return 0;
+		if ( value > 0xff )
+			return 0;
+		*(byte++) = value;
+		if ( *endp != *separator )
+			return 0;
+		if ( ! *(separator++) )
+			return 1;
+		string = ( endp + 1 );
+	}
+}
+
 /**
  * Convert IPv4 address to dotted-quad notation
  *
- * @v in	IP address
- * @ret string	IP address in dotted-quad notation
+ * @v in		IPv4 address
+ * @ret string		IPv4 address in dotted-quad notation
  */
 char * inet_ntoa ( struct in_addr in ) {
 	static char buf[16]; /* "xxx.xxx.xxx.xxx" */
 }
 
 /**
- * Transcribe IP address
+ * Transcribe IPv4 address
  *
- * @v net_addr	IP address
- * @ret string	IP address in dotted-quad notation
+ * @v net_addr		IPv4 address
+ * @ret string		IPv4 address in dotted-quad notation
  *
  */
 static const char * ipv4_ntoa ( const void *net_addr ) {

src/tests/ipv4_test.c

 	inet_aton_fail_ok ( "256.0.0.1" ); /* Byte out of range */
 	inet_aton_fail_ok ( "212.13.204.60.1" ); /* Too long */
 	inet_aton_fail_ok ( "127.0.0" ); /* Too short */
+	inet_aton_fail_ok ( "1.2.3.a" ); /* Invalid characters */
+	inet_aton_fail_ok ( "127.0..1" ); /* Missing bytes */
 }
 
 /** IPv4 self-test */