LIBBLOCKLIST(3) Library Functions Manual LIBBLOCKLIST(3) NAME blocklist_open, blocklist_open2, blocklist_close, blocklist_r, blocklist, blocklist_sa, blocklist_sa_r -- Blocklistd notification library LIBRARY libblocklist SYNOPSIS #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); DESCRIPTION These functions can be used by daemons to notify blocklistd(8) about suc- cessful and failed remote connections so that blocklistd can block or re- lease 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 per- formed. 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 op- tional message in the msg argument. The action parameter can take these values: BLOCKLIST_AUTH_FAIL There was an unsuccessful authentication at- tempt. BLOCKLIST_AUTH_OK A user successfully authenticated. BLOCKLIST_ABUSIVE_BEHAVIOR The sending daemon has detected abusive behav- ior from the remote system. The remote address should be blocked as soon as possible. BLOCKLIST_BAD_USER The sending daemon has determined the username presented for authentication is invalid. The blocklistd(8) daemon compares the username to a configured list of forbidden usernames and blocks the address immediately if a forbidden username matches. (The BLOCKLIST_BAD_USER sup- port is not currently available.) 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 uncon- nected 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 lo- cal endpoint using getsockname(2). By default, syslogd(8) is used for message logging. The internal bl_cre- ate() function can be used to create the required internal state and spec- ify a custom logging function. RETURN VALUES The function blocklist_open() returns a cookie on success and NULL on fail- ure 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. SEE ALSO blocklistd.conf(5), blocklistd(8) AUTHORS Christos Zoulas FreeBSD 15.1 February 5, 2025 LIBBLOCKLIST(3)
NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | SEE ALSO | AUTHORS
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