LD_PRELOAD hack for working on the kdbus bridge

dbus-redirect.c

/* gcc -fPIC -shared -o dbus-redirect.so dbus-redirect.c -ldl */

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <dlfcn.h>

int connect(int sockfd, const struct sockaddr *addr, socklen_t addrlen)
{
        int (*f)() = dlsym((void *) -1, "connect");
        struct sockaddr_un *a = (struct sockaddr_un *) addr;
        int ret, do_free = 0;

        if (a->sun_family == AF_UNIX &&
            strcmp(a->sun_path, "/var/run/dbus/system_bus_socket") == 0) {
                a = (struct sockaddr_un *) malloc(addrlen);
                if (!a)
                        return -1;

                memcpy(a, addr, addrlen);
                strcpy(a->sun_path, "/run/systemd/dbus-bridge/system");
                do_free = 1;
        }

        ret = f(sockfd, a, addrlen);

        if (do_free)
                free(a);

        return ret;
}