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//this program was written to be used on NetBSD. YMMV.
#include <string.h>
#include <sys/param.h>
#include <sys/socket.h>
#include <sys/sysctl.h>
#include <netinet/in.h>
#include <netinet/ip_var.h>
#include <netinet/tcp.h>
#include <netinet/tcp_timer.h>
#include <netinet/tcp_var.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <stdio.h>
//ripped from NetBSD's identd.c (found mine in /usr/src/libexec/identd/identd.c)
static int
sysctl_getuid(struct sockaddr_storage *ss, socklen_t len, uid_t *uid)
{
int mib[4];
uid_t myuid;
size_t uidlen;
uidlen = sizeof(myuid);
mib[0] = CTL_NET;
mib[1] = ss->ss_family;
mib[2] = IPPROTO_TCP;
mib[3] = TCPCTL_IDENT;
if (sysctl(mib, sizeof(mib)/ sizeof(int), &myuid, &uidlen, ss, len) < 0)
return -1;
*uid = myuid;
return 0;
}
//for debugging
void dump_sockaddr(struct sockaddr_in *sin,int len) {
unsigned char *p=(void *)sin;
for(;len;len--,p++) {
printf("%02x ",*p);
}
printf("\n");
}
int main(int argc,char *argv[]) {
uid_t myuid=-1;
int len=sizeof(struct sockaddr_storage);
struct sockaddr_storage mine[2];
//future IPv6 support?
struct sockaddr_in *inA=(struct sockaddr_in *)(&mine[0]);
// struct sockaddr_in6 *in6A=(struct sockaddr_in6 *)(&mine[0]);
struct sockaddr_in *inB=(struct sockaddr_in *)(&mine[1]);
// struct sockaddr_in6 *in6B=(struct sockaddr_in6 *)(&mine[1]);
if(argc <= 4) return -2;
memset(inA,0,len);
memset(inB,0,len);
inA->sin_len=16;
inB->sin_len=16;
inA->sin_family=AF_INET;
inB->sin_family=AF_INET;
inA->sin_addr.s_addr=(inet_addr(argv[1]));
inB->sin_addr.s_addr=(inet_addr(argv[3]));
inA->sin_port=htons(atoi(argv[2]));
inB->sin_port=htons(atoi(argv[4]));
//these were to see what real sockaddr looked like.
// getpeername(0,inB,&len);
// getsockname(0,inA,&len);
// dump_sockaddr(inA,len);
// dump_sockaddr(inB,len);
if(sysctl_getuid(mine,sizeof(mine),&myuid) == -1) return -1;
printf("%d\n",myuid);
return 0;
}
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