Diff: dns-server/dnserver.c

Revision:

1:119c4f7144c8

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dns-server/dnserver.c	Tue Jul 24 17:36:01 2018 +0000
@@ -0,0 +1,200 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2015 by Sergey Fetisov <fsenok@gmail.com>
+ * 
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * 
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+/*
+ * version: 1.0 demo (7.02.2015)
+ * brief:   tiny dns ipv4 server using lwip (pcb)
+ */
+
+#include "dnserver.h"
+
+#define DNS_MAX_HOST_NAME_LEN 128
+
+static struct udp_pcb *pcb = NULL;
+dns_query_proc_t query_proc = NULL;
+
+#pragma pack(push, 1)
+typedef struct
+{
+#if BYTE_ORDER == LITTLE_ENDIAN
+	uint8_t rd: 1,     /* Recursion Desired */
+	        tc: 1,     /* Truncation Flag */
+	        aa: 1,     /* Authoritative Answer Flag */
+	        opcode: 4, /* Operation code */
+	        qr: 1;     /* Query/Response Flag */
+	uint8_t rcode: 4,  /* Response Code */
+	        z: 3,      /* Zero */
+	        ra: 1;     /* Recursion Available */
+#else
+	uint8_t qr: 1,     /* Query/Response Flag */
+	        opcode: 4, /* Operation code */
+	        aa: 1,     /* Authoritative Answer Flag */
+	        tc: 1,     /* Truncation Flag */
+	        rd: 1;     /* Recursion Desired */
+	uint8_t ra: 1,     /* Recursion Available */
+	        z: 3,      /* Zero */
+	        rcode: 4;  /* Response Code */
+#endif
+} dns_header_flags_t;
+
+typedef struct
+{
+	uint16_t id;
+	dns_header_flags_t flags;
+	uint16_t n_record[4];
+} dns_header_t;
+
+typedef struct dns_answer
+{
+	uint16_t name;
+	uint16_t type;
+	uint16_t Class;
+	uint32_t ttl;
+	uint16_t len;
+	uint32_t addr;
+} dns_answer_t;
+#pragma pack(pop)
+
+typedef struct dns_query
+{
+	char name[DNS_MAX_HOST_NAME_LEN];
+	uint16_t type;
+	uint16_t Class;
+} dns_query_t;
+
+static int parse_next_query(void *data, int size, dns_query_t *query)
+{
+	int len;
+	int lables;
+	uint8_t *ptr;
+
+	len = 0;
+	lables = 0;
+	ptr = (uint8_t *)data;
+
+	while (true)
+	{
+		uint8_t lable_len;
+		if (size <= 0) return -1;
+		lable_len = *ptr++;
+		size--;
+		if (lable_len == 0) break;
+		if (lables > 0)
+		{
+			if (len == DNS_MAX_HOST_NAME_LEN) return -2;
+			query->name[len++] = '.';
+		}
+		if (lable_len > size) return -1;
+		if (len + lable_len >= DNS_MAX_HOST_NAME_LEN) return -2;
+		memcpy(&query->name[len], ptr, lable_len);
+		len += lable_len;
+		ptr += lable_len;
+		size -= lable_len;
+		lables++;
+	}
+
+	if (size < 4) return -1;
+	query->name[len] = 0;
+	query->type = *(uint16_t *)ptr;
+	ptr += 2;
+	query->Class = *(uint16_t *)ptr;
+	ptr += 2;
+	return ptr - (uint8_t *)data;
+}
+
+static void udp_recv_proc(void *arg, struct udp_pcb *upcb, struct pbuf *p, struct ip_addr *addr, u16_t port)
+{
+	int len;
+	dns_header_t *header;
+	static dns_query_t query;
+	struct pbuf *out;
+	ip_addr_t host_addr;
+	dns_answer_t *answer;
+
+	if (p->len <= sizeof(dns_header_t)) goto error;
+	header = (dns_header_t *)p->payload;
+	if (header->flags.qr != 0) goto error;
+	if (ntohs(header->n_record[0]) != 1) goto error;
+
+	len = parse_next_query(header + 1, p->len - sizeof(dns_header_t), &query);
+	if (len < 0) goto error;
+	if (!query_proc(query.name, &host_addr)) goto refuse;
+
+	len += sizeof(dns_header_t);
+	out = pbuf_alloc(PBUF_TRANSPORT, len + 16, PBUF_POOL);
+	if (out == NULL) goto error;
+
+	memcpy(out->payload, p->payload, len);
+	header = (dns_header_t *)out->payload;
+	header->flags.qr = 1;
+	header->n_record[1] = htons(1);
+	answer = (struct dns_answer *)((uint8_t *)out->payload + len);
+	answer->name = htons(0xC00C);
+	answer->type = htons(1);
+	answer->Class = htons(1);
+	answer->ttl = htonl(32);
+	answer->len = htons(4);
+	answer->addr = host_addr.addr;
+	
+	udp_sendto(upcb, out, addr, port);
+	pbuf_free(out);
+	pbuf_free(p);
+	return;
+
+refuse:
+	header->flags.qr = 1;
+	header->flags.rcode = 5;
+	udp_sendto(upcb, p, addr, port);
+	pbuf_free(p);
+	return;
+
+error:
+	pbuf_free(p);
+}
+
+err_t dnserv_init(ip_addr_t *bind, uint16_t port, dns_query_proc_t qp)
+{
+	err_t err;
+	udp_init();
+	dnserv_free();
+	pcb = udp_new();
+	if (pcb == NULL)
+		return ERR_MEM;
+	err = udp_bind(pcb, bind, port);
+	if (err != ERR_OK)
+	{
+		dnserv_free();
+		return err;
+	}
+	udp_recv(pcb, udp_recv_proc, NULL);
+	query_proc = qp;
+	return ERR_OK;
+}
+
+void dnserv_free()
+{
+	if (pcb == NULL) return;
+	udp_remove(pcb);
+	pcb = NULL;
+}