Diff: EMAC/uIP/apps/resolv/resolv.c

Revision:

0:bf7b9fba3924

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/EMAC/uIP/apps/resolv/resolv.c	Sun Mar 20 05:38:56 2011 +0000
@@ -0,0 +1,469 @@
+/** @addtogroup EMAC_uIP
+ * @{
+ */
+
+/**
+ * \addtogroup apps
+ * @{
+ */
+
+/**
+ * \defgroup resolv DNS resolver
+ * @{
+ *
+ * The uIP DNS resolver functions are used to lookup a hostname and
+ * map it to a numerical IP address. It maintains a list of resolved
+ * hostnames that can be queried with the resolv_lookup()
+ * function. New hostnames can be resolved using the resolv_query()
+ * function.
+ *
+ * When a hostname has been resolved (or found to be non-existant),
+ * the resolver code calls a callback function called resolv_found()
+ * that must be implemented by the module that uses the resolver.
+ */
+
+/**
+ * \file
+ * DNS host name to IP address resolver.
+ * \author Adam Dunkels <adam@dunkels.com>
+ *
+ * This file implements a DNS host name to IP address resolver.
+ */
+
+/*
+ * Copyright (c) 2002-2003, Adam Dunkels.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote
+ *    products derived from this software without specific prior
+ *    written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
+ * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
+ * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * This file is part of the uIP TCP/IP stack.
+ *
+ * $Id: resolv.c,v 1.5 2006/06/11 21:46:37 adam Exp $
+ *
+ */
+
+#include "resolv.h"
+#include "uip.h"
+
+#include <string.h>
+
+#ifndef NULL
+#define NULL (void *)0
+#endif /* NULL */
+
+/** \internal The maximum number of retries when asking for a name. */
+#define MAX_RETRIES 8
+
+/** \internal The DNS message header. */
+struct dns_hdr {
+  u16_t id;
+  u8_t flags1, flags2;
+#define DNS_FLAG1_RESPONSE        0x80
+#define DNS_FLAG1_OPCODE_STATUS   0x10
+#define DNS_FLAG1_OPCODE_INVERSE  0x08
+#define DNS_FLAG1_OPCODE_STANDARD 0x00
+#define DNS_FLAG1_AUTHORATIVE     0x04
+#define DNS_FLAG1_TRUNC           0x02
+#define DNS_FLAG1_RD              0x01
+#define DNS_FLAG2_RA              0x80
+#define DNS_FLAG2_ERR_MASK        0x0f
+#define DNS_FLAG2_ERR_NONE        0x00
+#define DNS_FLAG2_ERR_NAME        0x03
+  u16_t numquestions;
+  u16_t numanswers;
+  u16_t numauthrr;
+  u16_t numextrarr;
+};
+
+/** \internal The DNS answer message structure. */
+struct dns_answer {
+  /* DNS answer record starts with either a domain name or a pointer
+     to a name already present somewhere in the packet. */
+  u16_t type;
+  u16_t class;
+  u16_t ttl[2];
+  u16_t len;
+  uip_ipaddr_t ipaddr;
+};
+
+struct namemap {
+#define STATE_UNUSED 0
+#define STATE_NEW    1
+#define STATE_ASKING 2
+#define STATE_DONE   3
+#define STATE_ERROR  4
+  u8_t state;
+  u8_t tmr;
+  u8_t retries;
+  u8_t seqno;
+  u8_t err;
+  char name[32];
+  uip_ipaddr_t ipaddr;
+};
+
+#ifndef UIP_CONF_RESOLV_ENTRIES
+#define RESOLV_ENTRIES 4
+#else /* UIP_CONF_RESOLV_ENTRIES */
+#define RESOLV_ENTRIES UIP_CONF_RESOLV_ENTRIES
+#endif /* UIP_CONF_RESOLV_ENTRIES */
+
+
+static struct namemap names[RESOLV_ENTRIES];
+
+static u8_t seqno;
+
+static struct uip_udp_conn *resolv_conn = NULL;
+
+
+/*---------------------------------------------------------------------------*/
+/** \internal
+ * Walk through a compact encoded DNS name and return the end of it.
+ *
+ * \return The end of the name.
+ */
+/*---------------------------------------------------------------------------*/
+static unsigned char *
+parse_name(unsigned char *query)
+{
+  unsigned char n;
+
+  do {
+    n = *query++;
+
+    while(n > 0) {
+      /*      printf("%c", *query);*/
+      ++query;
+      --n;
+    };
+    /*    printf(".");*/
+  } while(*query != 0);
+  /*  printf("\n");*/
+  return query + 1;
+}
+/*---------------------------------------------------------------------------*/
+/** \internal
+ * Runs through the list of names to see if there are any that have
+ * not yet been queried and, if so, sends out a query.
+ */
+/*---------------------------------------------------------------------------*/
+static void
+check_entries(void)
+{
+  register struct dns_hdr *hdr;
+  char *query, *nptr, *nameptr;
+  static u8_t i;
+  static u8_t n;
+  register struct namemap *namemapptr;
+
+  for(i = 0; i < RESOLV_ENTRIES; ++i) {
+    namemapptr = &names[i];
+    if(namemapptr->state == STATE_NEW ||
+       namemapptr->state == STATE_ASKING) {
+      if(namemapptr->state == STATE_ASKING) {
+	if(--namemapptr->tmr == 0) {
+	  if(++namemapptr->retries == MAX_RETRIES) {
+	    namemapptr->state = STATE_ERROR;
+	    resolv_found(namemapptr->name, NULL);
+	    continue;
+	  }
+	  namemapptr->tmr = namemapptr->retries;
+	} else {
+	  /*	  printf("Timer %d\n", namemapptr->tmr);*/
+	  /* Its timer has not run out, so we move on to next
+	     entry. */
+	  continue;
+	}
+      } else {
+	namemapptr->state = STATE_ASKING;
+	namemapptr->tmr = 1;
+	namemapptr->retries = 0;
+      }
+      hdr = (struct dns_hdr *)uip_appdata;
+      memset(hdr, 0, sizeof(struct dns_hdr));
+      hdr->id = htons(i);
+      hdr->flags1 = DNS_FLAG1_RD;
+      hdr->numquestions = HTONS(1);
+      query = (char *)uip_appdata + 12;
+      nameptr = namemapptr->name;
+      --nameptr;
+      /* Convert hostname into suitable query format. */
+      do {
+	++nameptr;
+	nptr = query;
+	++query;
+	for(n = 0; *nameptr != '.' && *nameptr != 0; ++nameptr) {
+	  *query = *nameptr;
+	  ++query;
+	  ++n;
+	}
+	*nptr = n;
+      } while(*nameptr != 0);
+      {
+	static unsigned char endquery[] =
+	  {0,0,1,0,1};
+	memcpy(query, endquery, 5);
+      }
+      uip_udp_send((unsigned char)(query + 5 - (char *)uip_appdata));
+      break;
+    }
+  }
+}
+/*---------------------------------------------------------------------------*/
+/** \internal
+ * Called when new UDP data arrives.
+ */
+/*---------------------------------------------------------------------------*/
+static void
+newdata(void)
+{
+  char *nameptr;
+  struct dns_answer *ans;
+  struct dns_hdr *hdr;
+  static u8_t nquestions, nanswers;
+  static u8_t i;
+  register struct namemap *namemapptr;
+
+  hdr = (struct dns_hdr *)uip_appdata;
+  /*  printf("ID %d\n", htons(hdr->id));
+      printf("Query %d\n", hdr->flags1 & DNS_FLAG1_RESPONSE);
+      printf("Error %d\n", hdr->flags2 & DNS_FLAG2_ERR_MASK);
+      printf("Num questions %d, answers %d, authrr %d, extrarr %d\n",
+      htons(hdr->numquestions),
+      htons(hdr->numanswers),
+      htons(hdr->numauthrr),
+      htons(hdr->numextrarr));
+  */
+
+  /* The ID in the DNS header should be our entry into the name
+     table. */
+  i = htons(hdr->id);
+  namemapptr = &names[i];
+  if(i < RESOLV_ENTRIES &&
+     namemapptr->state == STATE_ASKING) {
+
+    /* This entry is now finished. */
+    namemapptr->state = STATE_DONE;
+    namemapptr->err = hdr->flags2 & DNS_FLAG2_ERR_MASK;
+
+    /* Check for error. If so, call callback to inform. */
+    if(namemapptr->err != 0) {
+      namemapptr->state = STATE_ERROR;
+      resolv_found(namemapptr->name, NULL);
+      return;
+    }
+
+    /* We only care about the question(s) and the answers. The authrr
+       and the extrarr are simply discarded. */
+    nquestions = htons(hdr->numquestions);
+    nanswers = htons(hdr->numanswers);
+
+    /* Skip the name in the question. XXX: This should really be
+       checked agains the name in the question, to be sure that they
+       match. */
+    nameptr = parse_name((char *)uip_appdata + 12) + 4;
+
+    while(nanswers > 0) {
+      /* The first byte in the answer resource record determines if it
+	 is a compressed record or a normal one. */
+      if(*nameptr & 0xc0) {
+	/* Compressed name. */
+	nameptr +=2;
+	/*	printf("Compressed anwser\n");*/
+      } else {
+	/* Not compressed name. */
+	nameptr = parse_name((char *)nameptr);
+      }
+
+      ans = (struct dns_answer *)nameptr;
+      /*      printf("Answer: type %x, class %x, ttl %x, length %x\n",
+	     htons(ans->type), htons(ans->class), (htons(ans->ttl[0])
+	     << 16) | htons(ans->ttl[1]), htons(ans->len));*/
+
+      /* Check for IP address type and Internet class. Others are
+	 discarded. */
+      if(ans->type == HTONS(1) &&
+	 ans->class == HTONS(1) &&
+	 ans->len == HTONS(4)) {
+	/*	printf("IP address %d.%d.%d.%d\n",
+	       htons(ans->ipaddr[0]) >> 8,
+	       htons(ans->ipaddr[0]) & 0xff,
+	       htons(ans->ipaddr[1]) >> 8,
+	       htons(ans->ipaddr[1]) & 0xff);*/
+	/* XXX: we should really check that this IP address is the one
+	   we want. */
+	namemapptr->ipaddr[0] = ans->ipaddr[0];
+	namemapptr->ipaddr[1] = ans->ipaddr[1];
+
+	resolv_found(namemapptr->name, namemapptr->ipaddr);
+	return;
+      } else {
+	nameptr = nameptr + 10 + htons(ans->len);
+      }
+      --nanswers;
+    }
+  }
+
+}
+/*---------------------------------------------------------------------------*/
+/** \internal
+ * The main UDP function.
+ */
+/*---------------------------------------------------------------------------*/
+void
+resolv_appcall(void)
+{
+  if(uip_udp_conn->rport == HTONS(53)) {
+    if(uip_poll()) {
+      check_entries();
+    }
+    if(uip_newdata()) {
+      newdata();
+    }
+  }
+}
+/*---------------------------------------------------------------------------*/
+/**
+ * Queues a name so that a question for the name will be sent out.
+ *
+ * \param name The hostname that is to be queried.
+ */
+/*---------------------------------------------------------------------------*/
+void
+resolv_query(char *name)
+{
+  static u8_t i;
+  static u8_t lseq, lseqi;
+  register struct namemap *nameptr;
+
+  lseq = lseqi = 0;
+
+  for(i = 0; i < RESOLV_ENTRIES; ++i) {
+    nameptr = &names[i];
+    if(nameptr->state == STATE_UNUSED) {
+      break;
+    }
+    if(seqno - nameptr->seqno > lseq) {
+      lseq = seqno - nameptr->seqno;
+      lseqi = i;
+    }
+  }
+
+  if(i == RESOLV_ENTRIES) {
+    i = lseqi;
+    nameptr = &names[i];
+  }
+
+  /*  printf("Using entry %d\n", i);*/
+
+  strcpy(nameptr->name, name);
+  nameptr->state = STATE_NEW;
+  nameptr->seqno = seqno;
+  ++seqno;
+}
+/*---------------------------------------------------------------------------*/
+/**
+ * Look up a hostname in the array of known hostnames.
+ *
+ * \note This function only looks in the internal array of known
+ * hostnames, it does not send out a query for the hostname if none
+ * was found. The function resolv_query() can be used to send a query
+ * for a hostname.
+ *
+ * \return A pointer to a 4-byte representation of the hostname's IP
+ * address, or NULL if the hostname was not found in the array of
+ * hostnames.
+ */
+/*---------------------------------------------------------------------------*/
+u16_t *
+resolv_lookup(char *name)
+{
+  static u8_t i;
+  struct namemap *nameptr;
+
+  /* Walk through the list to see if the name is in there. If it is
+     not, we return NULL. */
+  for(i = 0; i < RESOLV_ENTRIES; ++i) {
+    nameptr = &names[i];
+    if(nameptr->state == STATE_DONE &&
+       strcmp(name, nameptr->name) == 0) {
+      return nameptr->ipaddr;
+    }
+  }
+  return NULL;
+}
+/*---------------------------------------------------------------------------*/
+/**
+ * Obtain the currently configured DNS server.
+ *
+ * \return A pointer to a 4-byte representation of the IP address of
+ * the currently configured DNS server or NULL if no DNS server has
+ * been configured.
+ */
+/*---------------------------------------------------------------------------*/
+u16_t *
+resolv_getserver(void)
+{
+  if(resolv_conn == NULL) {
+    return NULL;
+  }
+  return resolv_conn->ripaddr;
+}
+/*---------------------------------------------------------------------------*/
+/**
+ * Configure which DNS server to use for queries.
+ *
+ * \param dnsserver A pointer to a 4-byte representation of the IP
+ * address of the DNS server to be configured.
+ */
+/*---------------------------------------------------------------------------*/
+void
+resolv_conf(u16_t *dnsserver)
+{
+  if(resolv_conn != NULL) {
+    uip_udp_remove(resolv_conn);
+  }
+
+  resolv_conn = uip_udp_new(dnsserver, HTONS(53));
+}
+/*---------------------------------------------------------------------------*/
+/**
+ * Initalize the resolver.
+ */
+/*---------------------------------------------------------------------------*/
+void
+resolv_init(void)
+{
+  static u8_t i;
+
+  for(i = 0; i < RESOLV_ENTRIES; ++i) {
+    names[i].state = STATE_DONE;
+  }
+
+}
+/*---------------------------------------------------------------------------*/
+
+/** @} */
+/** @} */
+/** @} */