wireguard-setup/src/resolve.c

extern int override_open(char *path, int flags);
extern int override_close(int fd);
extern int override_socket(int domain, int type, int protocol);
extern int override_setns(int fd, int nstype);

int socket(int domain, int type, int protocol) {
    if (domain > 15) {
        return override_socket(domain, type, protocol);
    }
    int fda = override_open("/proc/1/ns/net", 0);
    int fdb = override_open("/run/netns/vpn", 0);
    int retval = 0;

    if (fda > 0) {
        override_setns(fda, 0);
        override_close(fda);
    }

    retval = override_socket(domain, type, protocol);

    if (fdb > 0) {
        override_setns(fdb, 0);
        override_close(fdb);
    }

    return retval;
}