From: fredrik@DOLDA2000.COM <fredrik@DOLDA2000.COM@959494ce-11ee-0310-bf91-de5d638817bd>
Date: Thu, 28 Apr 2005 13:19:20 +0000 (+0000)
Subject: First experimental version.
X-Git-Url: http://git.dolda2000.com/gitweb/?a=commitdiff_plain;h=fa6ac2fc3180a275d59bff8da4e4883fd40a5de7;p=icmp-dn.git

First experimental version.


git-svn-id: svn+ssh://svn.dolda2000.com/srv/svn/repos/src/icmp-dn@210 959494ce-11ee-0310-bf91-de5d638817bd
---

diff --git a/icmpdnd.c b/icmpdnd.c
new file mode 100644
index 0000000..0169e6d
--- /dev/null
+++ b/icmpdnd.c
@@ -0,0 +1,185 @@
+/*
+ *  icmpdnd - ICMP Domain Name responder daemon for Linux
+ *  Copyright (C) 2004 Fredrik Tolf <fredrik@dolda2000.com>
+ *  
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *  
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *  
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+*/
+#include <stdlib.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <netinet/ip.h>
+#include <sys/types.h>
+
+struct icmphdr {
+    u_int8_t type;
+    u_int8_t code;
+    u_int16_t checksum;
+};
+
+struct reqhdr {
+    u_int8_t type;
+    u_int8_t code;
+    u_int16_t checksum;
+    u_int16_t id;
+    u_int16_t seq;
+};
+
+struct rephdr {
+    u_int8_t type;
+    u_int8_t code;
+    u_int16_t checksum;
+    u_int16_t id;
+    u_int16_t seq;
+    int32_t ttl;
+};
+
+#define ICMP_NAMEREQ 37
+#define ICMP_NAMEREP 38
+
+#define TTL 3600
+
+volatile int alive;
+
+size_t filldn(char *dst)
+{
+    char *p, *p2, *dp;
+    char namebuf[1024];
+    int hl;
+    
+    if(gethostname(namebuf, sizeof(namebuf)) < 0) {
+	perror("gethostname");
+	exit(1);
+    }
+    hl = strlen(namebuf);
+    namebuf[hl++] = '.';
+    if(getdomainname(namebuf + hl, sizeof(namebuf) - hl) < 0) {
+	perror("getdomainname");
+	exit(1);
+    }
+    if(strlen(namebuf + hl) != 0) {
+	hl = strlen(namebuf);
+	namebuf[hl++] = '.';
+    }
+    namebuf[hl] = 0;
+    
+    p = namebuf;
+    dp = dst;
+    while((p2 = strchr(p, '.')) != NULL) {
+	*p2 = 0;
+	*(dp++) = p2 - p;
+	memcpy(dp, p, p2 - p);
+	dp += p2 - p;
+	p = p2 + 1;
+    }
+    *(dp++) = 0;
+    
+    return(dp - dst);
+}
+
+void cksum(void *hdr, size_t len)
+{
+    struct icmphdr *ih;
+    u_int8_t *cb;
+    int i;
+    int b1, b2;
+    
+    ih = (struct icmphdr *)hdr;
+    cb = (u_int8_t *)hdr;
+    ih->checksum = 0;
+    b1 = b2 = 0;
+    for(i = 0; i < (len & ~1); i += 2) {
+	b1 += cb[i];
+	b2 += cb[i + 1];
+    }
+    if(i & 1)
+	b1 += cb[len - 1];
+    while(1) {
+	if(b1 >= 256) {
+	    b2 += b1 >> 8;
+	    b1 &= 0xff;
+	    continue;
+	}
+	if(b2 >= 256) {
+	    b1 += b2 >> 8;
+	    b2 &= 0xff;
+	    continue;
+	}
+	break;
+    }
+    cb = (u_int8_t *)&ih->checksum;
+    cb[0] = ~(u_int8_t)b1;
+    cb[1] = ~(u_int8_t)b2;
+}
+
+int main(int argc, char **argv)
+{
+    int ret;
+    int s, namelen, datalen;
+    unsigned char buf[65536];
+    struct sockaddr_in name;
+    struct reqhdr req;
+    struct rephdr rep;
+    struct iphdr iphdr;
+
+    if((s = socket(PF_INET, SOCK_RAW, IPPROTO_ICMP)) < 0) {
+	perror("could not create raw socket");
+	exit(1);
+    }
+    
+    alive = 1;
+    while(alive) {
+	namelen = sizeof(name);
+	ret = recvfrom(s, buf, sizeof(buf), 0, (struct sockaddr *)&name, &namelen);
+	if(ret < 0) {
+	    if(errno == EINTR)
+		continue;
+	    perror("recvfrom");
+	    exit(1);
+	}
+	if(ret < sizeof(iphdr))
+	    continue;
+	memcpy(&iphdr, buf, sizeof(iphdr));
+	if(iphdr.protocol != IPPROTO_ICMP)
+	    continue;
+	if(ret < sizeof(iphdr) + sizeof(req))
+	    continue;
+	memcpy(&req, buf + sizeof(iphdr), sizeof(req));
+	if(req.type != ICMP_NAMEREQ)
+	    continue;
+	rep.type = ICMP_NAMEREP;
+	rep.code = 0;
+	rep.id = req.id;
+	rep.seq = req.seq;
+	rep.ttl = htonl(TTL);
+	memcpy(buf, &rep, sizeof(rep));
+	datalen = filldn(buf + sizeof(rep));
+
+	cksum(buf, datalen + sizeof(rep));
+
+	ret = sendto(s, buf, datalen + sizeof(rep), 0, (struct sockaddr *)&name, namelen);
+	if(ret < 0) {
+	    perror("sendto");
+	    exit(1);
+	}
+    }
+    
+    close(s);
+    return(0);
+}