udhcpc: shrink code by setting xid more economically

function                                             old     new   delta
send_decline                                          90      82      -8
udhcpc_main                                         2649    2640      -9

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 8 insertions, 4 deletions

diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index 43d682341..945600c6b 100644
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -726,7 +726,7 @@ static NOINLINE int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr)
 #if ENABLE_FEATURE_UDHCPC_ARPING
 /* Broadcast a DHCP decline message */
 /* NOINLINE: limit stack usage in caller */
-static NOINLINE int send_decline(uint32_t xid, uint32_t server, uint32_t requested)
+static NOINLINE int send_decline(/*uint32_t xid,*/ uint32_t server, uint32_t requested)
 {
         struct dhcp_packet packet;
 
@@ -735,12 +735,14 @@ static NOINLINE int send_decline(uint32_t xid, uint32_t server, uint32_t request
          */
         init_packet(&packet, DHCPDECLINE);
 
+#if 0
         /* RFC 2131 says DHCPDECLINE's xid is randomly selected by client,
          * but in case the server is buggy and wants DHCPDECLINE's xid
          * to match the xid which started entire handshake,
          * we use the same xid we used in initial DHCPDISCOVER:
          */
         packet.xid = xid;
+#endif
         /* DHCPDECLINE uses "requested ip", not ciaddr, to store offered IP */
         udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 
@@ -1131,7 +1133,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
         int discover_retries = 3;
         uint32_t server_addr = server_addr; /* for compiler */
         uint32_t requested_ip = 0;
-        uint32_t xid = 0;
+        uint32_t xid = xid; /* for compiler */
         int packet_num;
         int timeout; /* must be signed */
         unsigned already_waited_sec;
@@ -1520,7 +1522,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 
                 switch (state) {
                 case INIT_SELECTING:
-                        /* Must be a DHCPOFFER to one of our xid's */
+                        /* Must be a DHCPOFFER */
                         if (*message == DHCPOFFER) {
 /* What exactly is server's IP? There are several values.
  * Example DHCP offer captured with tchdump:
@@ -1600,7 +1602,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
                                         ) {
                                                 bb_info_msg("Offered address is in use "
                                                         "(got ARP reply), declining");
-                                                send_decline(xid, server_addr, packet.yiaddr);
+                                                send_decline(/*xid,*/ server_addr, packet.yiaddr);
 
                                                 if (state != REQUESTING)
                                                         udhcp_run_script(NULL, "deconfig");
@@ -1637,6 +1639,8 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
                                         opt = ((opt & ~OPT_b) | OPT_f);
                                 }
 #endif
+                                /* make future renew packets use different xid */
+                                /* xid = random_xid(); ...but why bother? */
                                 already_waited_sec = 0;
                                 continue; /* back to main loop */
                         }