udhcpc[6]: do not pass xid around, keep it in client_data.xid

function                                             old     new   delta
perform_release                                      105     169     +64
perform_d6_release                                   259     262      +3
init_d6_packet                                        84      85      +1
send_d6_discover                                     286     285      -1
send_d6_select                                       128     126      -2
send_d6_renew                                        176     174      -2
send_d6_info_request                                  65      63      -2
udhcpc_main                                         2555    2551      -4
send_select                                          130     122      -8
send_renew                                            99      91      -8
send_discover                                         89      81      -8
udhcpc6_main                                        2636    2602     -34
send_release                                          74       -     -74
------------------------------------------------------------------------------
(add/remove: 0/1 grow/shrink: 3/9 up/down: 68/-143)           Total: -75 bytes

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

3 files changed, 48 insertions, 60 deletions

diff --git a/networking/udhcp/d6_dhcpc.c b/networking/udhcp/d6_dhcpc.c
index 7f288f891..802a27521 100644
--- a/networking/udhcp/d6_dhcpc.c
+++ b/networking/udhcp/d6_dhcpc.c
@@ -479,15 +479,15 @@ static ALWAYS_INLINE uint32_t random_xid(void)
 }
 
 /* Initialize the packet with the proper defaults */
-static uint8_t *init_d6_packet(struct d6_packet *packet, char type, uint32_t xid)
+static uint8_t *init_d6_packet(struct d6_packet *packet, char type)
 {
         uint8_t *ptr;
         unsigned secs;
 
         memset(packet, 0, sizeof(*packet));
 
-        packet->d6_xid32 = xid;
-        packet->d6_msg_type = type;
+        packet->d6_xid32 = client_data.xid;
+        packet->d6_msg_type = type; /* union, overwrites lowest byte of d6_xid32 */
 
         /* ELAPSED_TIME option is required to be present by the RFC,
          * and some servers do check for its presense. [which?]
@@ -585,13 +585,13 @@ static int d6_mcast_from_client_data_ifindex(struct d6_packet *packet, uint8_t *
  * about parameter values the client would like to have returned.
  */
 /* NOINLINE: limit stack usage in caller */
-static NOINLINE int send_d6_info_request(uint32_t xid)
+static NOINLINE int send_d6_info_request(void)
 {
         struct d6_packet packet;
         uint8_t *opt_ptr;
 
-        /* Fill in: msg type */
-        opt_ptr = init_d6_packet(&packet, D6_MSG_INFORMATION_REQUEST, xid);
+        /* Fill in: msg type, xid, ELAPSED_TIME */
+        opt_ptr = init_d6_packet(&packet, D6_MSG_INFORMATION_REQUEST);
 
         /* Add options: client-id,
          * "param req" option according to -O, options specified with -x
@@ -684,14 +684,14 @@ static NOINLINE int send_d6_info_request(uint32_t xid)
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  */
 /* NOINLINE: limit stack usage in caller */
-static NOINLINE int send_d6_discover(uint32_t xid, struct in6_addr *requested_ipv6)
+static NOINLINE int send_d6_discover(struct in6_addr *requested_ipv6)
 {
         struct d6_packet packet;
         uint8_t *opt_ptr;
         unsigned len;
 
-        /* Fill in: msg type */
-        opt_ptr = init_d6_packet(&packet, D6_MSG_SOLICIT, xid);
+        /* Fill in: msg type, xid, ELAPSED_TIME */
+        opt_ptr = init_d6_packet(&packet, D6_MSG_SOLICIT);
 
         /* Create new IA_NA, optionally with included IAADDR with requested IP */
         free(client6_data.ia_na);
@@ -763,13 +763,13 @@ static NOINLINE int send_d6_discover(uint32_t xid, struct in6_addr *requested_ip
  * messages from the server.
  */
 /* NOINLINE: limit stack usage in caller */
-static NOINLINE int send_d6_select(uint32_t xid)
+static NOINLINE int send_d6_select(void)
 {
         struct d6_packet packet;
         uint8_t *opt_ptr;
 
-        /* Fill in: msg type */
-        opt_ptr = init_d6_packet(&packet, D6_MSG_REQUEST, xid);
+        /* Fill in: msg type, xid, ELAPSED_TIME */
+        opt_ptr = init_d6_packet(&packet, D6_MSG_REQUEST);
 
         /* server id */
         opt_ptr = mempcpy(opt_ptr, client6_data.server_id, client6_data.server_id->len + 2+2);
@@ -836,13 +836,13 @@ static NOINLINE int send_d6_select(uint32_t xid)
  * about parameter values the client would like to have returned.
  */
 /* NOINLINE: limit stack usage in caller */
-static NOINLINE int send_d6_renew(uint32_t xid, struct in6_addr *server_ipv6, struct in6_addr *our_cur_ipv6)
+static NOINLINE int send_d6_renew(struct in6_addr *server_ipv6, struct in6_addr *our_cur_ipv6)
 {
         struct d6_packet packet;
         uint8_t *opt_ptr;
 
-        /* Fill in: msg type */
-        opt_ptr = init_d6_packet(&packet, DHCPREQUEST, xid);
+        /* Fill in: msg type, xid, ELAPSED_TIME */
+        opt_ptr = init_d6_packet(&packet, DHCPREQUEST);
 
         /* server id */
         opt_ptr = mempcpy(opt_ptr, client6_data.server_id, client6_data.server_id->len + 2+2);
@@ -877,8 +877,8 @@ int send_d6_release(struct in6_addr *server_ipv6, struct in6_addr *our_cur_ipv6)
         uint8_t *opt_ptr;
         struct option_set *ci;
 
-        /* Fill in: msg type, client id */
-        opt_ptr = init_d6_packet(&packet, D6_MSG_RELEASE, random_xid());
+        /* Fill in: msg type, xid, ELAPSED_TIME */
+        opt_ptr = init_d6_packet(&packet, D6_MSG_RELEASE);
         /* server id */
         opt_ptr = mempcpy(opt_ptr, client6_data.server_id, client6_data.server_id->len + 2+2);
         /* IA NA (contains our current IP) */
@@ -1097,6 +1097,7 @@ static void perform_d6_release(struct in6_addr *server_ipv6, struct in6_addr *ou
          || client_data.state == RENEW_REQUESTED
         ) {
                 bb_simple_info_msg("unicasting a release");
+                client_data.xid = random_xid(); //TODO: can omit?
                 send_d6_release(server_ipv6, our_cur_ipv6); /* unicast */
         }
         bb_simple_info_msg("entering released state");
@@ -1183,7 +1184,6 @@ int udhcpc6_main(int argc UNUSED_PARAM, char **argv)
         struct in6_addr srv6_buf;
         struct in6_addr ipv6_buf;
         struct in6_addr *requested_ipv6;
-        uint32_t xid = 0;
         int packet_num;
         int timeout; /* must be signed */
         int lease_remaining; /* must be signed */
@@ -1387,13 +1387,13 @@ int udhcpc6_main(int argc UNUSED_PARAM, char **argv)
                                 if (!discover_retries || packet_num < discover_retries) {
                                         if (packet_num == 0) {
                                                 change_listen_mode(LISTEN_RAW);
-                                                xid = random_xid();
+                                                client_data.xid = random_xid();
                                         }
                                         /* multicast */
                                         if (opt & OPT_l)
-                                                send_d6_info_request(xid);
+                                                send_d6_info_request();
                                         else
-                                                send_d6_discover(xid, requested_ipv6);
+                                                send_d6_discover(requested_ipv6);
                                         timeout = discover_timeout;
                                         packet_num++;
                                         continue;
@@ -1427,7 +1427,7 @@ int udhcpc6_main(int argc UNUSED_PARAM, char **argv)
                         case REQUESTING:
                                 if (!discover_retries || packet_num < discover_retries) {
                                         /* send multicast select packet */
-                                        send_d6_select(xid);
+                                        send_d6_select();
                                         timeout = discover_timeout;
                                         packet_num++;
                                         continue;
@@ -1459,9 +1459,9 @@ int udhcpc6_main(int argc UNUSED_PARAM, char **argv)
                          * into INIT_SELECTING state.
                          */
                                         if (opt & OPT_l)
-                                                send_d6_info_request(xid);
+                                                send_d6_info_request();
                                         else
-                                                send_d6_renew(xid, &srv6_buf, requested_ipv6);
+                                                send_d6_renew(&srv6_buf, requested_ipv6);
                                         timeout = discover_timeout;
                                         packet_num++;
                                         continue;
@@ -1484,9 +1484,9 @@ int udhcpc6_main(int argc UNUSED_PARAM, char **argv)
                                  * try to find DHCP server using broadcast */
                                 if (lease_remaining > 0 && packet_num < 3) {
                                         if (opt & OPT_l)
-                                                send_d6_info_request(xid);
+                                                send_d6_info_request();
                                         else /* send a broadcast renew request */
-                                                send_d6_renew(xid, /*server_ipv6:*/ NULL, requested_ipv6);
+                                                send_d6_renew(/*server_ipv6:*/ NULL, requested_ipv6);
                                         timeout = discover_timeout;
                                         packet_num++;
                                         continue;
@@ -1581,9 +1581,9 @@ int udhcpc6_main(int argc UNUSED_PARAM, char **argv)
                         packet_end = (uint8_t*)&packet + len;
                 }
 
-                if ((packet.d6_xid32 & htonl(0x00ffffff)) != xid) {
+                if ((packet.d6_xid32 & htonl(0x00ffffff)) != client_data.xid) {
                         log1("xid %x (our is %x)%s",
-                                (unsigned)(packet.d6_xid32 & htonl(0x00ffffff)), (unsigned)xid,
+                                (unsigned)(packet.d6_xid32 & htonl(0x00ffffff)), (unsigned)client_data.xid,
                                 ", ignoring packet"
                         );
                         continue;
diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index b80ea2f40..1c3c478ac 100644
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -605,7 +605,7 @@ static void init_packet(struct dhcp_packet *packet, char type)
         /* Fill in: op, htype, hlen, cookie fields; message type option: */
         udhcp_init_header(packet, type);
 
-        packet->xid = random_xid();
+        packet->xid = client_data.xid;
 
         client_data.last_secs = monotonic_sec();
         if (client_data.first_secs == 0)
@@ -719,17 +719,15 @@ static int bcast_or_ucast(struct dhcp_packet *packet, uint32_t ciaddr, uint32_t
 
 /* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
 /* NOINLINE: limit stack usage in caller */
-static NOINLINE int send_discover(uint32_t xid, uint32_t requested)
+static NOINLINE int send_discover(uint32_t requested)
 {
         struct dhcp_packet packet;
 
         /* Fill in: op, htype, hlen, cookie, chaddr fields,
-         * random xid field (we override it below),
-         * message type option:
+         * xid field, message type option:
          */
         init_packet(&packet, DHCPDISCOVER);
 
-        packet.xid = xid;
         if (requested)
                 udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 
@@ -747,7 +745,7 @@ static NOINLINE int send_discover(uint32_t xid, uint32_t requested)
  * "The client _broadcasts_ a DHCPREQUEST message..."
  */
 /* NOINLINE: limit stack usage in caller */
-static NOINLINE int send_select(uint32_t xid, uint32_t server, uint32_t requested)
+static NOINLINE int send_select(uint32_t server, uint32_t requested)
 {
         struct dhcp_packet packet;
         struct in_addr temp_addr;
@@ -766,12 +764,10 @@ static NOINLINE int send_select(uint32_t xid, uint32_t server, uint32_t requeste
  * include that list in all subsequent messages.
  */
         /* Fill in: op, htype, hlen, cookie, chaddr fields,
-         * random xid field (we override it below),
-         * message type option:
+         * xid field, message type option:
          */
         init_packet(&packet, DHCPREQUEST);
 
-        packet.xid = xid;
         udhcp_add_simple_option(&packet, DHCP_REQUESTED_IP, requested);
 
         udhcp_add_simple_option(&packet, DHCP_SERVER_ID, server);
@@ -793,7 +789,7 @@ static NOINLINE int send_select(uint32_t xid, uint32_t server, uint32_t requeste
 
 /* Unicast or broadcast a DHCP renew message */
 /* NOINLINE: limit stack usage in caller */
-static NOINLINE int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr)
+static NOINLINE int send_renew(uint32_t server, uint32_t ciaddr)
 {
         struct dhcp_packet packet;
 
@@ -812,12 +808,10 @@ static NOINLINE int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr)
  * replying to the client.
  */
         /* Fill in: op, htype, hlen, cookie, chaddr fields,
-         * random xid field (we override it below),
-         * message type option:
+         * xid field, message type option:
          */
         init_packet(&packet, DHCPREQUEST);
 
-        packet.xid = xid;
         packet.ciaddr = ciaddr;
 
         /* Add options: maxsize,
@@ -839,7 +833,7 @@ 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 server, uint32_t requested)
 {
         struct dhcp_packet packet;
 
@@ -848,14 +842,6 @@ static NOINLINE int send_decline(/*uint32_t xid,*/ uint32_t server, uint32_t req
          */
         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);
 
@@ -1145,6 +1131,7 @@ static void perform_release(uint32_t server_addr, uint32_t requested_ip)
                 temp_addr.s_addr = requested_ip;
                 bb_info_msg("unicasting a release of %s to %s",
                                 inet_ntoa(temp_addr), buffer);
+                client_data.xid = random_xid(); //TODO: can omit?
                 send_release(server_addr, requested_ip); /* unicast */
         }
         bb_simple_info_msg("entering released state");
@@ -1233,7 +1220,6 @@ 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 = xid; /* for compiler */
         int packet_num;
         int timeout; /* must be signed */
         int lease_remaining; /* must be signed */
@@ -1458,10 +1444,10 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
                                 if (!discover_retries || packet_num < discover_retries) {
                                         if (packet_num == 0) {
                                                 change_listen_mode(LISTEN_RAW);
-                                                xid = random_xid();
+                                                client_data.xid = random_xid();
                                         }
                                         /* broadcast */
-                                        send_discover(xid, requested_ip);
+                                        send_discover(requested_ip);
                                         timeout = discover_timeout;
                                         packet_num++;
                                         continue;
@@ -1495,7 +1481,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
                         case REQUESTING:
                                 if (packet_num < 3) {
                                         /* send broadcast select packet */
-                                        send_select(xid, server_addr, requested_ip);
+                                        send_select(server_addr, requested_ip);
                                         timeout = discover_timeout;
                                         packet_num++;
                                         continue;
@@ -1526,7 +1512,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
                          * Anyway, it does recover by eventually failing through
                          * into INIT_SELECTING state.
                          */
-                                        if (send_renew(xid, server_addr, requested_ip) >= 0) {
+                                        if (send_renew(server_addr, requested_ip) >= 0) {
                                                 timeout = discover_timeout;
                                                 packet_num++;
                                                 continue;
@@ -1555,7 +1541,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
                                  * try to find DHCP server using broadcast */
                                 if (lease_remaining > 0 && packet_num < 3) {
                                         /* send a broadcast renew request */
-                                        send_renew(xid, 0 /*INADDR_ANY*/, requested_ip);
+                                        send_renew(0 /*INADDR_ANY*/, requested_ip);
                                         timeout = discover_timeout;
                                         packet_num++;
                                         continue;
@@ -1648,9 +1634,9 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
                                 continue;
                 }
 
-                if (packet.xid != xid) {
+                if (packet.xid != client_data.xid) {
                         log1("xid %x (our is %x)%s",
-                                (unsigned)packet.xid, (unsigned)xid,
+                                (unsigned)packet.xid, (unsigned)client_data.xid,
                                 ", ignoring packet"
                         );
                         continue;
@@ -1779,7 +1765,8 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
                                         ) {
                                                 bb_simple_info_msg("offered address is in use "
                                                         "(got ARP reply), declining");
-                                                send_decline(/*xid,*/ server_addr, packet.yiaddr);
+                                                client_data.xid = random_xid(); //TODO: can omit?
+                                                send_decline(server_addr, packet.yiaddr);
 
                                                 if (client_data.state != REQUESTING)
                                                         d4_run_script_deconfig();
@@ -1814,7 +1801,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
                                 timeout = (unsigned)lease_remaining / 2;
                                 client_data.state = BOUND;
                                 /* make future renew packets use different xid */
-                                /* xid = random_xid(); ...but why bother? */
+                                /* client_data.xid = random_xid(); ...but why bother? */
                                 packet_num = 0;
                                 continue; /* back to main loop */
                         }
diff --git a/networking/udhcp/dhcpc.h b/networking/udhcp/dhcpc.h
index cd9ead6bd..19b054b32 100644
--- a/networking/udhcp/dhcpc.h
+++ b/networking/udhcp/dhcpc.h
@@ -11,6 +11,7 @@ struct client_data_t {
         uint8_t client_mac[6];          /* Our mac address */
         IF_FEATURE_UDHCP_PORT(uint16_t port;)
         int ifindex;                    /* Index number of the interface to use */
+        uint32_t xid;
         uint8_t opt_mask[256 / 8];      /* Bitmask of options to send (-O option) */
 // ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ TODO: DHCPv6 has 16-bit option numbers
         const char *interface;          /* The name of the interface to use */