| LIBBLOCKLIST(3) | Library Functions Manual | LIBBLOCKLIST(3) |
blocklist_open,
blocklist_open2,
blocklist_close,
blocklist_r, blocklist,
blocklist_sa, blocklist_sa_r
— Blocklistd notification library
library “libblocklist”
#include
<blocklist.h>
struct blocklist *
blocklist_open(void);
struct blocklist *
blocklist_open2(void
(*logger)(int, struct syslog_data *, va_list));
void
blocklist_close(struct
blocklist *cookie);
int
blocklist(int
action, int fd,
const char *msg);
int
blocklist_r(struct
blocklist *cookie, int
action, int fd,
const char *msg);
int
blocklist_sa(int
action, int fd,
const struct sockaddr
*sa, socklen_t
salen, const char
*msg);
int
blocklist_sa_r(struct
blocklist *cookie, int
action, int fd,
const struct sockaddr
*sa, socklen_t
salen, const char
*msg);
These functions can be used by daemons to notify blocklistd(8) about successful and failed remote connections so that blocklistd can block or release port access to prevent Denial of Service attacks.
The function
blocklist_open()
creates the necessary state to communicate with
blocklistd(8) and returns
a pointer to it, or NULL on failure.
The function
blocklist_open2()
is similar to blocklist_open() but allows a
logger to be specified. If the
logger is NULL, then no
logging is performed.
The
blocklist_close()
function frees all memory and resources used.
The
blocklist()
function sends a message to
blocklistd(8), with an
integer action argument specifying the type of
notification, a file descriptor fd specifying the
accepted file descriptor connected to the client, and an optional message in
the msg argument.
The action parameter can take these values:
The
blocklist_r()
function is more efficient because it keeps the blocklist state around.
The
blocklist_sa()
and
blocklist_sa_r()
functions can be used with unconnected sockets, where
getpeername(2) will not
work, the server will pass the peer name in the message.
In all cases the file descriptor passed in the fd argument must be pointing to a valid socket so that blocklistd(8) can establish ownership of the local endpoint using getsockname(2).
By default,
syslogd(8) is used for
message logging. The internal
bl_create()
function can be used to create the required internal state and specify a
custom logging function.
The function blocklist_open() returns a
cookie on success and NULL on failure setting
errno to an appropriate value.
The functions blocklist(),
blocklist_sa(), and
blocklist_sa_r() return 0 on
success and -1 on failure setting
errno to an appropriate value.
Christos Zoulas
| February 5, 2025 | NetBSD 11.0 |