# ATS hook EVENT
```c
/**
This set of enums represents the possible hooks where you can
set up continuation callbacks. The functions used to register a
continuation for a particular hook are:
TSHttpHookAdd: adds a global hook. You can globally add
any hook except for
- TS_HTTP_REQUEST_TRANSFORM_HOOK
- TS_HTTP_RESPONSE_TRANSFORM_HOOK
- TS_HTTP_RESPONSE_CLIENT_HOOK
The following hooks can ONLY be added globally:
- TS_HTTP_SELECT_ALT_HOOK
- TS_HTTP_SSN_START_HOOK
- TS_HTTP_SSN_CLOSE_HOOK
TSHttpSsnHookAdd: adds a transaction hook to each transaction
within a session. You can only use transaction hooks with this call:
- TS_HTTP_READ_REQUEST_HDR_HOOK
- TS_HTTP_OS_DNS_HOOK
- TS_HTTP_SEND_REQUEST_HDR_HOOK
- TS_HTTP_READ_CACHE_HDR_HOOK
- TS_HTTP_READ_RESPONSE_HDR_HOOK
- TS_HTTP_SEND_RESPONSE_HDR_HOOK
- TS_HTTP_REQUEST_TRANSFORM_HOOK
- TS_HTTP_RESPONSE_TRANSFORM_HOOK
- TS_HTTP_RESPONSE_CLIENT_HOOK
- TS_HTTP_TXN_START_HOOK
- TS_HTTP_TXN_CLOSE_HOOK
TSHttpTxnHookAdd: adds a callback at a specific point within
an HTTP transaction. The following hooks can be used with this
function:
- TS_HTTP_READ_REQUEST_HDR_HOOK
- TS_HTTP_OS_DNS_HOOK
- TS_HTTP_SEND_REQUEST_HDR_HOOK
- TS_HTTP_READ_CACHE_HDR_HOOK
- TS_HTTP_READ_RESPONSE_HDR_HOOK
- TS_HTTP_SEND_RESPONSE_HDR_HOOK
- TS_HTTP_REQUEST_TRANSFORM_HOOK
- TS_HTTP_RESPONSE_TRANSFORM_HOOK
- TS_HTTP_TXN_CLOSE_HOOK
The two transform hooks can ONLY be added as transaction hooks.
TS_VCONN_PRE_ACCEPT_HOOK - Called before the SSL hand
shake starts. No handshake data has been read or sent (from the
proxy) at this point
TS_HTTP_LAST_HOOK _must_ be the last element. Only right place
to insert a new element is just before TS_HTTP_LAST_HOOK.
*/
```
