/* wrapper.c: * * Simple wrapper example: */ #include #include #include #include #include #include #include #include #include #include "log.h" #define LOGPATH "/tmp/wrapper.log" int main(int argc,char **argv,char **envp) { int z; struct sockaddr_in adr_clnt; /* Client */ int alen; /* Address length */ char dgram[512]; /* Receive buffer */ char *str_addr; /* String form of addr */ /* * We must log denied attempts : */ if ( log_open(LOGPATH) == -1 ) exit(1); /* Can't open log file! */ log("wrapper started.\n"); /* * Peek at datagram using MSG_PEEK : */ alen = sizeof adr_clnt; /* length */ z = recvfrom(0, /* Socket on std input */ dgram, /* Receiving buffer */ sizeof dgram, /* Max recv size */ MSG_PEEK, /* Flags: Peek!!!!!! */ (struct sockaddr *)&adr_clnt, &alen); /* Addr len, in & out */ if ( z < 0 ) bail("recvfrom(2), peeking at client" " address."); /* * Convert IP address to string form: */ str_addr = inet_ntoa(adr_clnt.sin_addr); if ( strcmp(str_addr,"127.7.7.7") != 0 ) { /* * Not our special 127.7.7.7 address: */ log("Address %s port %d rejected.\n", str_addr, ntohs(adr_clnt.sin_port)); /* * We must read this packet now without * the MSG_PEEK option to discard dgram: */ z = recvfrom(0, /* Socket */ dgram, /* Receiving buffer */ sizeof dgram, /* Max rcv size */ 0, /* No flags!! */ (struct sockaddr *)&adr_clnt, &alen); if ( z < 0 ) bail("recvfrom(2), eating dgram"); exit(1); } /* * Accept this dgram request, and * launch the server: */ log("Address %s port %d accepted.\n", str_addr, ntohs(adr_clnt.sin_port)); /* * inetd has provided argv[0] from the * config file /etc/inetd.conf: we have * used this to indicate the server's * full pathname for this example. We * simply pass any other arguments and * environment as is. */ log("Starting '%s'\n",argv[0]); log_close(); /* No longer need this */ z = execve(argv[0],argv,envp); /* * If control returns, then execve(2) * failed for some reason: */ log_open(LOGPATH); /* Re-open log */ bail("execve(2), starting server"); return 1; }
