package: busybox
version: 1.36.1
Busybox DHCP client is RFC-3442 (option 121) compliant according to the
documentations. However, it's stated under section "DHCP Client Behavior" that
"
DHCP clients that support this option and send a parameter request
list MAY also request the Static Routes option, for compatibility
with older servers that don't support Classless Static Routes. The
Classless Static Routes option code MUST appear in the parameter
request list prior to both the Router option code and the Static
Routes option code, if present.
"This requirement is currently not fulfilled. Instead, the "add_client_options"
function pulls the options from the struct in common.c, in the same order as
they are defined. Placing option 121 further down. The patch attached to this
email solves this issue by modifying the placement of the option while
generating the request section in the "add_client_options" function. As this
ordering requirement is only true when option 121 is selected, I choose to not
modify the order in the struct. Aside from the risk of breaking other
functionality.
diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index c757fb37c..9bc0039bf 100644
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -627,8 +627,20 @@ static void add_client_options(struct dhcp_packet *packet)
* No bounds checking because it goes towards the head of the packet. */
end = udhcp_end_option(packet->options);
len = 0;
+ /* If option 121 requested. Place it before option 3 and 33 in parameter
+ * request list in accordance with RFC-3442 */
for (i = 1; i < DHCP_END; i++) {
+ if (i == 121) {
+ /* Skipping 121 as it's placed before option 3 (when i == 3) */
+ continue;
+ }
if (client_data.opt_mask[i >> 3] & (1 << (i & 7))) {
+ if (i == 3) {
+ if (client_data.opt_mask[121 >> 3] & (1 << (121 & 7))) {
+ packet->options[end + OPT_DATA + len] = 121;
+ len++;
+ }
+ }
packet->options[end + OPT_DATA + len] = i;
len++;
}
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