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 (file)
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);
+}