diff --git a/FILES b/FILES
index 5134d2da..66253196 100644
--- a/FILES
+++ b/FILES
@@ -1,4 +1,4 @@
 src/      - The source code for the lwIP TCP/IP stack.
-doc/      - Documentation on the lwIP APIs.
+doc/      - The documentation for lwIP.
 
 See also the FILES file in each subdirectory.
diff --git a/src/core/dhcp.c b/src/core/dhcp.c
index d545ab60..afd2c15b 100644
--- a/src/core/dhcp.c
+++ b/src/core/dhcp.c
@@ -154,19 +154,13 @@ static void dhcp_handle_nak(struct netif *netif) {
 static void dhcp_check(struct netif *netif)
 {
   struct dhcp *dhcp = netif->dhcp;
-  struct pbuf *p;
   err_t result;
   u16_t msecs;
   DEBUGF(DHCP_DEBUG | DBG_TRACE, ("dhcp_check()\n"));
   /* create an ARP query for the offered IP address, expecting that no host
      responds, as the IP address should not be in use. */
-  p = etharp_query(netif, &dhcp->offered_ip_addr, NULL);
-  if (p != NULL) {
-    DEBUGF(DHCP_DEBUG | DBG_TRACE, ("dhcp_check(): sending ARP request len %u\n", p->tot_len));
-    result = netif->linkoutput(netif, p);
-    pbuf_free(p);
-    p = NULL;
-  }	else {
+  result = etharp_query(netif, &dhcp->offered_ip_addr, NULL);
+  if (result != ERR_OK) {
     DEBUGF(DHCP_DEBUG | DBG_TRACE | 2, ("dhcp_check: could not perform ARP query\n"));
   }
   dhcp->tries++;
diff --git a/src/core/ipv4/ip.c b/src/core/ipv4/ip.c
index af088606..13f38e76 100644
--- a/src/core/ipv4/ip.c
+++ b/src/core/ipv4/ip.c
@@ -494,7 +494,7 @@ ip_output_if(struct pbuf *p, struct ip_addr *src, struct ip_addr *dest,
 #ifdef IP_STATS
   lwip_stats.ip.xmit++;
 #endif /* IP_STATS */
-  DEBUGF(IP_DEBUG, ("ip_output_if: %c%c ", netif->name[0], netif->name[1]));
+  DEBUGF(IP_DEBUG, ("ip_output_if: %c%c%u\n", netif->name[0], netif->name[1], netif->num));
 #if IP_DEBUG
   ip_debug_print(p);
 #endif /* IP_DEBUG */
diff --git a/src/core/netif.c b/src/core/netif.c
index 117d1393..b85c043a 100644
--- a/src/core/netif.c
+++ b/src/core/netif.c
@@ -176,8 +176,8 @@ void
 netif_set_ipaddr(struct netif *netif, struct ip_addr *ipaddr)
 {
   ip_addr_set(&(netif->ip_addr), ipaddr);
-  DEBUGF(NETIF_DEBUG, ("netif: setting IP address of interface %c%c to %d.%d.%d.%d\n",
-		       netif->name[0], netif->name[1],
+  DEBUGF(NETIF_DEBUG | DBG_TRACE | DBG_STATE, ("netif: setting IP address of interface %c%c%u to %u.%u.%u.%u\n",
+		       netif->name[0], netif->name[1], netif->num,
 		       (u8_t)(ntohl(ipaddr->addr) >> 24 & 0xff),
 		       (u8_t)(ntohl(ipaddr->addr) >> 16 & 0xff),
 		       (u8_t)(ntohl(ipaddr->addr) >> 8 & 0xff),
@@ -188,12 +188,24 @@ void
 netif_set_gw(struct netif *netif, struct ip_addr *gw)
 {
   ip_addr_set(&(netif->gw), gw);
+  DEBUGF(NETIF_DEBUG | DBG_TRACE | DBG_STATE, ("netif: setting GW address of interface %c%c%u to %u.%u.%u.%u\n",
+		       netif->name[0], netif->name[1], netif->num,
+		       (u8_t)(ntohl(gw->addr) >> 24 & 0xff),
+		       (u8_t)(ntohl(gw->addr) >> 16 & 0xff),
+		       (u8_t)(ntohl(gw->addr) >> 8 & 0xff),
+		       (u8_t)(ntohl(gw->addr) & 0xff)));
 }
 /*-----------------------------------------------------------------------------------*/
 void
 netif_set_netmask(struct netif *netif, struct ip_addr *netmask)
 {
   ip_addr_set(&(netif->netmask), netmask);
+  DEBUGF(NETIF_DEBUG | DBG_TRACE | DBG_STATE, ("netif: setting netmask of interface %c%c%u to %u.%u.%u.%u\n",
+		       netif->name[0], netif->name[1], netif->num,
+		       (u8_t)(ntohl(netmask->addr) >> 24 & 0xff),
+		       (u8_t)(ntohl(netmask->addr) >> 16 & 0xff),
+		       (u8_t)(ntohl(netmask->addr) >> 8 & 0xff),
+		       (u8_t)(ntohl(netmask->addr) & 0xff)));
 }
 /*-----------------------------------------------------------------------------------*/
 void
diff --git a/src/core/tcp_in.c b/src/core/tcp_in.c
index dafe949a..93c9a78f 100644
--- a/src/core/tcp_in.c
+++ b/src/core/tcp_in.c
@@ -184,7 +184,7 @@ tcp_input(struct pbuf *p, struct netif *inp)
     prev = pcb;
   }
 
-  if(pcb == NULL) {
+  if (pcb == NULL) {
     /* If it did not go to an active connection, we check the connections
        in the TIME-WAIT state. */
 
diff --git a/src/core/udp.c b/src/core/udp.c
index a81e69a3..3797fee3 100644
--- a/src/core/udp.c
+++ b/src/core/udp.c
@@ -410,14 +410,14 @@ udp_send(struct udp_pcb *pcb, struct pbuf *p)
       /* chksum zero must become 0xffff, as zero means 'no checksum' */
       if(udphdr->chksum == 0x0000) udphdr->chksum = 0xffff;
     }
-    DEBUGF(UDP_DEBUG, ("udp_send: UDP checksum %x\n", udphdr->chksum));
+    DEBUGF(UDP_DEBUG, ("udp_send: UDP checksum 0x%04x\n", udphdr->chksum));
     snmp_inc_udpoutdatagrams();
     DEBUGF(UDP_DEBUG, ("udp_send: ip_output_if(,,,,IP_PROTO_UDP,)\n"));
     /* output to IP */
     err = ip_output_if(q, src_ip, &pcb->remote_ip, UDP_TTL, IP_PROTO_UDP, netif);    
   }
 
-  /* did we chain a header? */
+  /* did we chain a header earlier? */
   if (q != p) {
     /* free the header */
     pbuf_free(q);
@@ -504,7 +504,11 @@ udp_bind(struct udp_pcb *pcb, struct ip_addr *ipaddr, u16_t port)
     pcb->next = udp_pcbs;
     udp_pcbs = pcb;
   }  
-  DEBUGF(UDP_DEBUG, ("udp_bind: bound to port %u\n", port));
+  DEBUGF(UDP_DEBUG | DBG_TRACE | DBG_STATE, ("udp_bind: bound to %u.%u.%u.%u, port %u\n",
+		       (u8_t)(ntohl(ipaddr->addr) >> 24 & 0xff),
+		       (u8_t)(ntohl(ipaddr->addr) >> 16 & 0xff),
+		       (u8_t)(ntohl(ipaddr->addr) >> 8 & 0xff),
+		       (u8_t)(ntohl(ipaddr->addr) & 0xff), port));
   return ERR_OK;
 }
 /**
diff --git a/src/include/lwip/pbuf.h b/src/include/lwip/pbuf.h
index 48f48951..a2f60365 100644
--- a/src/include/lwip/pbuf.h
+++ b/src/include/lwip/pbuf.h
@@ -59,7 +59,7 @@ typedef enum {
 #define PBUF_FLAG_ROM   0x01    /* Flags that pbuf data is stored in ROM. */
 #define PBUF_FLAG_POOL  0x02    /* Flags that the pbuf comes from the
 				   pbuf pool. */
-#define PBUF_FLAG_REF   0x03
+#define PBUF_FLAG_REF   0x04
 
 struct pbuf {
   struct pbuf *next;
diff --git a/src/include/netif/etharp.h b/src/include/netif/etharp.h
index 6432943b..765548f0 100644
--- a/src/include/netif/etharp.h
+++ b/src/include/netif/etharp.h
@@ -91,7 +91,7 @@ struct pbuf *etharp_arp_input(struct netif *netif, struct eth_addr *ethaddr,
 			   struct pbuf *p);
 struct pbuf *etharp_output(struct netif *netif, struct ip_addr *ipaddr,
 			   struct pbuf *q);
-struct pbuf *etharp_query(struct netif *netif, struct ip_addr *ipaddr, struct pbuf *q);
+err_t etharp_query(struct netif *netif, struct ip_addr *ipaddr, struct pbuf *q);
 
 
 
diff --git a/src/netif/etharp.c b/src/netif/etharp.c
index a0f05996..0a4a652f 100644
--- a/src/netif/etharp.c
+++ b/src/netif/etharp.c
@@ -638,11 +638,12 @@ etharp_output(struct netif *netif, struct ip_addr *ipaddr, struct pbuf *q)
  * TODO: use the ctime field to see how long ago an ARP request was sent,
  * possibly retry.
  */
-struct pbuf *etharp_query(struct netif *netif, struct ip_addr *ipaddr, struct pbuf *q)
+err_t etharp_query(struct netif *netif, struct ip_addr *ipaddr, struct pbuf *q)
 {
   struct eth_addr *srcaddr;
   struct etharp_hdr *hdr;
   struct pbuf *p;
+  err_t result;
   u8_t i;
 
   srcaddr = (struct eth_addr *)netif->hwaddr;
@@ -651,24 +652,23 @@ struct pbuf *etharp_query(struct netif *netif, struct ip_addr *ipaddr, struct pb
     if(ip_addr_cmp(ipaddr, &arp_table[i].ipaddr)) {
       if (arp_table[i].state == ETHARP_STATE_PENDING) {
         DEBUGF(ETHARP_DEBUG | DBG_TRACE | DBG_STATE, ("etharp_query: requested IP already pending as entry %u\n", i));
-        /* break out of for-loop */
+        /* break out of for-loop, user may wish to queue a packet on a stable entry */
         break;
       }
       else if (arp_table[i].state == ETHARP_STATE_STABLE) {
         DEBUGF(ETHARP_DEBUG | DBG_TRACE | DBG_STATE, ("etharp_query: requested IP already stable as entry %u\n", i));
+        /* TODO: user may wish to queue a packet on a stable entry. */
         return NULL;
       }
     }
   }
-  /* queried address not yet pending in ARP table? */
-  if (i == ARP_TABLE_SIZE)
-  {
+  /* queried address not yet in ARP table? */
+  if (i == ARP_TABLE_SIZE) {
     DEBUGF(ETHARP_DEBUG | DBG_TRACE, ("etharp_query: IP address not found in ARP table\n"));
     /* find an available entry */
     i = find_arp_entry();
     /* bail out if no ARP entries are available */
-    if(i == ARP_TABLE_SIZE)
-    {
+    if (i == ARP_TABLE_SIZE) {
       DEBUGF(ETHARP_DEBUG | 2, ("etharp_query: no more ARP entries available.\n"));
       return NULL;
     }
@@ -686,10 +686,10 @@ struct pbuf *etharp_query(struct netif *netif, struct ip_addr *ipaddr, struct pb
   if ((q != NULL) && (arp_table[i].p == NULL)) {
     /* copy PBUF_REF referenced payloads to PBUF_RAM */
     q = pbuf_take(q);
-    /* pbufs are queued, increase the reference count */
-    pbuf_ref(q);
     /* remember pbuf to queue, if any */
     arp_table[i].p = q;
+    /* pbufs are queued, increase the reference count */
+    pbuf_ref(q);
     DEBUGF(ETHARP_DEBUG | DBG_TRACE | DBG_STATE, ("etharp_query: queued packet %p on ARP entry %u.\n", (void *)q, i));
   }
 #endif
@@ -721,12 +721,13 @@ struct pbuf *etharp_query(struct netif *netif, struct ip_addr *ipaddr, struct pb
     }
     hdr->ethhdr.type = htons(ETHTYPE_ARP);      
     /* send ARP query */
-    netif->linkoutput(netif, p);
+    result = netif->linkoutput(netif, p);
     /* free ARP query packet */
     pbuf_free(p);
     p = NULL;
   } else {
+    result = ERR_MEM;
     DEBUGF(ETHARP_DEBUG | DBG_TRACE | 2, ("etharp_query: could not allocate pbuf for ARP request.\n"));
   }
-  return NULL;
+  return result;
 }