LIBBLACKLIST(3)

LIBBLACKLIST(3) | Library Functions Manual | LIBBLACKLIST(3)

# NAME

`blacklist_open`, `blacklist_close`, `blacklist_r`, `blacklist`, `blacklist_sa`, `blacklist_sa_r` —
Blacklistd notification library

# LIBRARY

library “libblacklist”

# SYNOPSIS

`#include <blacklist.h>`

struct blacklist *
`blacklist_open`(void);

void
`blacklist_close`(struct blacklist *cookie);

int
`blacklist`(int action, int fd, const char *msg);

int
`blacklist_r`(struct blacklist *cookie, int action, int fd, const char *msg);

int
`blacklist_sa`(int action, int fd, const struct sockaddr *sa, socklen_t salen, const char *msg);

int
`blacklist_sa_r`(struct blacklist *cookie, int action, int fd, const struct sockaddr *sa, socklen_t salen, const char *msg);

# DESCRIPTION

These functions can be used by daemons to notify blacklistd(8) about successful and failed remote connections so that blacklistd can block or release port access to prevent Denial of Service attacks.

The function `blacklist_open`() creates the necessary state to communicate with blacklistd(8) and returns a pointer to it, or `NULL` on failure.

The `blacklist_close`() function frees all memory and resources used.

The `blacklist`() function sends a message to blacklistd(8), with an action argument specifying `1` for a failed connection or `0` for a successful connection, a file descriptor fd specifying the accepted file descriptor connected to the client, and an optional message in the msg argument.

The `blacklist_r`() function is more efficient because it keeps the blacklist state around.

The `blacklist_sa`() and `blacklist_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.

All functions log errors to syslogd(8).

# RETURN VALUES

The function `blacklist_open`() returns a cookie on success and `NULL` on failure setting `errno` to an appropriate value.

The functions `blacklist`(), `blacklist_sa`(), and `blacklist_sa_r`() return `0` on success and `-1` on failure setting `errno` to an appropriate value.

# SEE ALSO

blacklistd.conf(5), blacklistd(8)

# AUTHORS

Christos Zoulas

January 22, 2015 | NetBSD 9.5