[PATCH 5/7] dhcp: add copy_only_if_valid support

[Jean-Christophe PLAGNIOL-VILLARD]

This will allow to only update a var if recive a valid data.
This is need for hostname.

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj at jcrosoft.com>
---
 net/dhcp.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/net/dhcp.c b/net/dhcp.c
index b4f2830..02dc529 100644
--- a/net/dhcp.c
+++ b/net/dhcp.c
@@ -110,6 +110,7 @@ struct dhcp_opt {
 	unsigned char option;
 	/* request automatically the option when creating the DHCP request */
 	bool optional;
+	bool copy_only_if_valid;
 	const char *barebox_var_name;
 	const char *barebox_dhcp_global;
 	void (*handle)(struct dhcp_opt *opt, unsigned char *data, int tlen);
@@ -153,6 +154,9 @@ static void env_str_handle(struct dhcp_opt *opt, unsigned char *popt, int optlen
 	memcpy(tmp, popt, optlen);
 	tmp[optlen] = 0;
 
+	if (opt->copy_only_if_valid && !strlen(tmp))
+		return;
+
 	if (opt->barebox_var_name)
 		setenv(opt->barebox_var_name, tmp);
 	if (opt->barebox_dhcp_global)
@@ -208,6 +212,7 @@ struct dhcp_opt dhcp_options[] = {
 		.barebox_var_name = "net.nameserver",
 	}, {
 		.option = 12,
+		.copy_only_if_valid = 1,
 		.handle = env_str_handle,
 		.barebox_var_name = "global.hostname",
 	}, {
@@ -647,7 +652,7 @@ static void dhcp_reset_env(void)
 
 	for (i = 0; i < ARRAY_SIZE(dhcp_options); i++) {
 		opt = &dhcp_options[i];
-		if (!opt->barebox_var_name)
+		if (!opt->barebox_var_name || opt->copy_only_if_valid)
 			continue;
 
 		setenv(opt->barebox_var_name,"");
-- 
1.7.10.4