Setting a Global Hook¶
Global hooks are always added in TSPluginInit
using
TSHttpHookAdd
. The two arguments of TSHttpHookAdd
are the hook
ID and the continuation to call when processing the event corresponding
to the hook. In blacklist-1.c
, the global hook is added as follows:
TSHttpHookAdd (TS_HTTP_OS_DNS_HOOK, contp);
Above, TS_HTTP_OS_DNS_HOOK
is the ID for the origin server DNS
lookup hook and contp
is the parent continuation created earlier.
This means that the Blacklist plugin is called at every origin server
DNS lookup. When it is called, the handler functio blacklist_plugin
receives TS_EVENT_HTTP_OS_DNS
and calls handle_dns
to see if the
request is forbidden.