Add DNS support

On 04 Oct 2008 Pieter posted a dns implementation for U-Boot.

http://www.mail-archive.com/u-boot-users@lists.sourceforge.net/msg10216.html
>
> DNS can be enabled by setting CFG_CMD_DNS. After performing a query,
> the serverip environment var is updated.
>
> Probably there are some cosmetic issues with the patch. Unfortunatly I
> do not have the time to correct these. So if anybody else likes DNS
> support in U-Boot and has the time, feel free to patch it in the main tree.

Here it is again - slightly modified & smaller:
  - update to 2009-06 (Pieter's patch was for U-Boot 1.2.0)
  - README.dns is added
  - syntax is changed (now takes a third option, the env var to store
    the result in)
  - add a random port() function in net.c
  - sort Makefile in ./net/Makefile
  - dns just returns unless a env var is given
  - run through checkpatch, and clean up style issues
  - remove packet from stack
  - cleaned up some comments
  - failure returns much faster (if server responds, don't wait for
    timeout)
  - use built in functions (memcpy) rather than byte copy.

Signed-off-by: Robin Getz <rgetz@blackfin.uclinux.org>
Signed-off-by: Pieter Voorthuijsen <pieter.voorthuijsen@prodrive.nl>
Signed-off-by: Ben Warren <biggerbadderben@gmail.com>

1 files changed, 211 insertions, 0 deletions

diff --git a/net/dns.c b/net/dns.c
new file mode 100644
index 000000000..f25c3f8c2
--- /dev/null
+++ b/net/dns.c
@@ -0,0 +1,211 @@
+/*
+ * DNS support driver
+ *
+ * Copyright (c) 2008 Pieter Voorthuijsen <pieter.voorthuijsen@prodrive.nl>
+ * Copyright (c) 2009 Robin Getz <rgetz@blackfin.uclinux.org>
+ *
+ * This is a simple DNS implementation for U-Boot. It will use the first IP
+ * in the DNS response as NetServerIP. This can then be used for any other
+ * network related activities.
+ *
+ * The packet handling is partly based on TADNS, original copyrights
+ * follow below.
+ *
+ */
+
+/*
+ * Copyright (c) 2004-2005 Sergey Lyubka <valenok@gmail.com>
+ *
+ * "THE BEER-WARE LICENSE" (Revision 42):
+ * Sergey Lyubka wrote this file.  As long as you retain this notice you
+ * can do whatever you want with this stuff. If we meet some day, and you think
+ * this stuff is worth it, you can buy me a beer in return.
+ */
+
+#include <common.h>
+#include <command.h>
+#include <net.h>
+
+#include "dns.h"
+
+char *NetDNSResolve;	/* The host to resolve  */
+char *NetDNSenvvar;	/* The envvar to store the answer in */
+
+static int DnsOurPort;
+
+static void
+DnsSend(void)
+{
+	struct header *header;
+	int n, name_len;
+	uchar *p, *pkt;
+	const char *s;
+	const char *name;
+	enum dns_query_type qtype = DNS_A_RECORD;
+
+	name = NetDNSResolve;
+	pkt = p = (uchar *)(NetTxPacket + NetEthHdrSize() + IP_HDR_SIZE);
+
+	/* Prepare DNS packet header */
+	header           = (struct header *) pkt;
+	header->tid      = 1;
+	header->flags    = htons(0x100);	/* standard query */
+	header->nqueries = htons(1);		/* Just one query */
+	header->nanswers = 0;
+	header->nauth    = 0;
+	header->nother   = 0;
+
+	/* Encode DNS name */
+	name_len = strlen(name);
+	p = (uchar *) &header->data;	/* For encoding host name into packet */
+
+	do {
+		s = strchr(name, '.');
+		if (!s)
+			s = name + name_len;
+
+		n = s - name;			/* Chunk length */
+		*p++ = n;			/* Copy length  */
+		memcpy(p, name, n);		/* Copy chunk   */
+		p += n;
+
+		if (*s == '.')
+			n++;
+
+		name += n;
+		name_len -= n;
+	} while (*s != '\0');
+
+	*p++ = 0;			/* Mark end of host name */
+	*p++ = 0;			/* Some servers require double null */
+	*p++ = (unsigned char) qtype;	/* Query Type */
+
+	*p++ = 0;
+	*p++ = 1;				/* Class: inet, 0x0001 */
+
+	n = p - pkt;				/* Total packet length */
+	debug("Packet size %d\n", n);
+
+	DnsOurPort = random_port();
+
+	NetSendUDPPacket(NetServerEther, NetOurDNSIP, DNS_SERVICE_PORT,
+		DnsOurPort, n);
+	debug("DNS packet sent\n");
+}
+
+static void
+DnsTimeout(void)
+{
+	puts("Timeout\n");
+	NetState = NETLOOP_FAIL;
+}
+
+static void
+DnsHandler(uchar *pkt, unsigned dest, unsigned src, unsigned len)
+{
+	struct header *header;
+	const unsigned char *p, *e, *s;
+	u16 type, i;
+	int found, stop, dlen;
+	char IPStr[22];
+	IPaddr_t IPAddress;
+	short tmp;
+
+
+	debug("%s\n", __func__);
+	if (dest != DnsOurPort)
+		return;
+
+	for (i = 0; i < len; i += 4)
+		debug("0x%p - 0x%.2x  0x%.2x  0x%.2x  0x%.2x\n",
+			pkt+i, pkt[i], pkt[i+1], pkt[i+2], pkt[i+3]);
+
+	/* We sent 1 query. We want to see more that 1 answer. */
+	header = (struct header *) pkt;
+	if (ntohs(header->nqueries) != 1)
+		return;
+
+	/* Received 0 answers */
+	if (header->nanswers == 0) {
+		puts("DNS server returned no answers\n");
+		NetState = NETLOOP_SUCCESS;
+		return;
+	}
+
+	/* Skip host name */
+	s = &header->data[0];
+	e = pkt + len;
+	for (p = s; p < e && *p != '\0'; p++)
+		continue;
+
+	/* We sent query class 1, query type 1 */
+	tmp = p[1] | (p[2] << 8);
+	if (&p[5] > e || ntohs(tmp) != DNS_A_RECORD) {
+		puts("DNS response was not A record\n");
+		NetState = NETLOOP_SUCCESS;
+		return;
+	}
+
+	/* Go to the first answer section */
+	p += 5;
+
+	/* Loop through the answers, we want A type answer */
+	for (found = stop = 0; !stop && &p[12] < e; ) {
+
+		/* Skip possible name in CNAME answer */
+		if (*p != 0xc0) {
+			while (*p && &p[12] < e)
+				p++;
+			p--;
+		}
+		debug("Name (Offset in header): %d\n", p[1]);
+
+		tmp = p[2] | (p[3] << 8);
+		type = ntohs(tmp);
+		debug("type = %d\n", type);
+		if (type == DNS_CNAME_RECORD) {
+			/* CNAME answer. shift to the next section */
+			debug("Found canonical name\n");
+			tmp = p[10] | (p[11] << 8);
+			dlen = ntohs(tmp);
+			debug("dlen = %d\n", dlen);
+			p += 12 + dlen;
+		} else if (type == DNS_A_RECORD) {
+			debug("Found A-record\n");
+			found = stop = 1;
+		} else {
+			debug("Unknown type\n");
+			stop = 1;
+		}
+	}
+
+	if (found && &p[12] < e) {
+
+		tmp = p[10] | (p[11] << 8);
+		dlen = ntohs(tmp);
+		p += 12;
+		memcpy(&IPAddress, p, 4);
+
+		if (p + dlen <= e) {
+			ip_to_string(IPAddress, IPStr);
+			printf("%s\n", IPStr);
+			if (NetDNSenvvar)
+				setenv(NetDNSenvvar, IPStr);
+		} else
+			puts("server responded with invalid IP number\n");
+	}
+
+	NetState = NETLOOP_SUCCESS;
+}
+
+void
+DnsStart(void)
+{
+	debug("%s\n", __func__);
+
+	NetSetTimeout(DNS_TIMEOUT, DnsTimeout);
+	NetSetHandler(DnsHandler);
+
+	DnsSend();
+}
+