Diff: TinyResolver.cpp

Revision:

0:477d4e2f281a

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/TinyResolver.cpp	Thu Jul 21 16:53:11 2011 +0000
@@ -0,0 +1,181 @@
+/*
+ * mbed Tiny DNS Resolver
+ * Copyright (c) 2011 Hiroshi Suga
+ * Released under the MIT License: http://mbed.org/license/mit
+ */
+
+/** @file
+ * @brief Tiny DNS Resolver
+ */
+
+#include "mbed.h"
+#include "EthernetNetIf.h"
+#include "UDPSocket.h"
+#include "TinyResolver.h"
+
+// host to network short
+#define htons( x ) ( (( (x) << 8 ) & 0xFF00) | (( (x) >> 8 ) & 0x00FF) )
+#define ntohs( x ) htons(x)
+// host to network long
+#define htonl( x ) ( (( (x) << 24 ) & 0xFF000000)  \
+                   | (( (x) <<  8 ) & 0x00FF0000)  \
+                   | (( (x) >>  8 ) & 0x0000FF00)  \
+                   | (( (x) >> 24 ) & 0x000000FF)  )
+#define ntohl( x ) htonl(x)
+
+extern EthernetNetIf eth;
+static UDPSocket *dns;
+static volatile unsigned long dnsaddr;
+static volatile unsigned long id;
+
+int createDnsRequest (char *name, char *buf) {
+    struct DnsHeader *dnsHeader;
+    struct DnsQuestionEnd *dnsEnd;
+    int len, num;
+
+    id ++;
+    dnsHeader = (struct DnsHeader*)buf;
+    dnsHeader->id = htons(id);
+    dnsHeader->flags = htons(0x100);
+    dnsHeader->questions = htons(1);
+    dnsHeader->answers = 0;
+    dnsHeader->authorities = 0;
+    dnsHeader->additional = 0;
+
+    len = sizeof(struct DnsHeader);
+    while ((num = (int)strchr(name, '.')) != NULL) {
+        num = num - (int)name;
+        buf[len] = num;
+        len ++;
+        strncpy(&buf[len], name, num); 
+        name = name + num + 1;
+        len = len + num;
+    }
+
+    if ((num = strlen(name)) != NULL) {
+        buf[len] = num;
+        len ++; 
+        strncpy(&buf[len], name, num); 
+        len = len + num;
+    }
+    buf[len] = 0;
+    len ++; 
+
+    dnsEnd = (struct DnsQuestionEnd *)&buf[len];
+    dnsEnd->type = htons(DNS_QUERY_A);
+    dnsEnd->clas = htons(DNS_CLASS_IN);
+
+    return len + sizeof(struct DnsQuestionEnd);
+}
+
+int getDnsResponse (const char *buf, int len, uint32_t *addr) {
+    int i;
+    struct DnsHeader *dnsHeader;
+    struct DnsAnswer *dnsAnswer;
+
+    // header
+    dnsHeader = (struct DnsHeader*)buf;
+    if (ntohs(dnsHeader->id) != id || (ntohs(dnsHeader->flags) & 0x800f) != 0x8000) {
+        return -1;
+    }
+
+    // skip question
+    for (i = sizeof(struct DnsHeader); buf[i] && i < len; i ++);
+    i = i + 1 + sizeof(struct DnsQuestionEnd);
+
+    // answer
+    while (i < len) {
+        dnsAnswer = (struct DnsAnswer*)&buf[i];
+
+        if (dnsAnswer->clas != htons(DNS_CLASS_IN)) {
+            return -1;
+        }
+
+        i = i + sizeof(struct DnsAnswer);
+        if (dnsAnswer->type == htons(DNS_QUERY_A)) {
+            // A record
+            *addr = ((uint32_t)buf[i] << 24) + ((uint32_t)buf[i + 1] << 16) + ((uint32_t)buf[i + 2] << 8) + (uint32_t)buf[i + 3];
+            return 0;
+        }
+        // next answer
+        i = i + dnsAnswer->length;
+    }
+
+    return -1;
+}
+
+void isr_dns (UDPSocketEvent e) {
+    char buf[512];
+    Host dsthost;
+    int len;
+
+    if (e == UDPSOCKET_READABLE) {
+        // recv responce;
+        len = dns->recvfrom(buf, sizeof(buf), &dsthost);
+#ifdef DEBUG
+        for (int i = 0; i < len; i ++) {
+            printf(" %02x", (unsigned char)buf[i]);
+        }
+        puts("\r");
+#endif
+        if (len >= sizeof(struct DnsHeader)) {
+            getDnsResponse(buf, len, (uint32_t*)&dnsaddr);
+        }
+    }
+}
+
+int getHostByName (IpAddr nameserver, const char *name, uint32_t *addr) {
+    UDPSocketErr err;
+    Host myhost, dnshost;
+    char buf[100];
+    int i, len;
+
+    // localhost
+    if (!strcmp(name, "localhost")) {
+        *addr = 0x0f000001;
+        return 0;
+    }
+
+    dnsaddr = 0;
+    dns = new UDPSocket;
+    dns->setOnEvent(isr_dns);
+
+    // bind
+    myhost.setIp(eth.getIp());
+    myhost.setPort(DNS_SRC_PORT);
+    err = dns->bind(myhost);
+    if (err != UDPSOCKET_OK) goto exit;
+
+    // send request
+    dnshost.setIp(nameserver);
+    dnshost.setPort(DNS_PORT);
+    len = createDnsRequest((char*)name, buf);
+#ifdef DEBUG
+    for (int i = 0; i < len; i ++) {
+        printf(" %02x", (unsigned char)buf[i]);
+    }
+    puts("\r");
+#endif
+    dns->sendto(buf, len, &dnshost);
+
+    // wait responce
+    for (i = 0; i < DNS_TIMEOUT / 10; i ++) {
+        if (dnsaddr) {
+            // responce
+            *addr = dnsaddr;
+            break;
+        }
+        if (i % 500 == 499) {
+            // retry
+            dns->sendto(buf, len, &dnshost);
+        }
+        Net::poll();
+        wait_ms(10);
+    }
+
+exit:
+    dns->resetOnEvent();
+    delete dns;
+
+    return dnsaddr ? 0 : -1;
+}