net: ipconfig: Don't override command-line hostnames or domains

If the user specifies a hostname or domain name as part of the ip=
command-line option, preserve it and don't overwrite it with one
supplied by DHCP/BOOTP.

For instance, ip=::::myhostname::dhcp will use "myhostname" rather than
ignoring and overwriting it.

Fix the comment on ic_bootp_string that suggests it only copies a string
"if not already set"; it doesn't have any such logic.
Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/ipconfig.c

@@ -886,7 +886,7 @@ static void __init ic_bootp_send_if(struct ic_device *d, unsigned long jiffies_d
 
 
 /*
- *  Copy BOOTP-supplied string if not already set.
+ *  Copy BOOTP-supplied string
  */
 static int __init ic_bootp_string(char *dest, char *src, int len, int max)
 {
@@ -935,11 +935,14 @@ static void __init ic_do_bootp_ext(u8 *ext)
 		}
 		break;
 	case 12:	/* Host name */
+		if (!ic_host_name_set) {
 			ic_bootp_string(utsname()->nodename, ext+1, *ext,
 					__NEW_UTS_LEN);
 			ic_host_name_set = 1;
+		}
 		break;
 	case 15:	/* Domain name (DNS) */
+		if (!ic_domain[0])
 			ic_bootp_string(ic_domain, ext+1, *ext, sizeof(ic_domain));
 		break;
 	case 17:	/* Root path */