Sendmail 8.13.3 Programmer's Guide

Milter APIs
Callbacks
Chapter 2 41
You must call xxfi_eoh() with the ctx argument, which specifies an
opaque context structure.
The xxfi_body() Callback
The xxfi_body() callback handles a portion of message body and
returns the SMFIS_CONTINUE value to the calling filter application. The
filter application calls xxfi_body() multiple times after calling the
xxfi_eoh() callback and before calling the xxfi_eom() callback.
The declaration of xxfi_body() is as follows:
#include <libmilter/mfapi.h>
sfsistat (*xxfi_body)(
SMFICTX * ctx,
unsigned char * bodyp,
size_t len
);
Following are some points to consider regarding xxfi_body():
• The bodyp argument points to a sequence of bytes and it is not a C
string that is a sequence of characters terminated by a null character
(\0). You must not use the normal C string functions, such as
strlen() to modify the block of data. The byte sequence in the block
can also contain \0 characters. If you add a trailing \0 character, C
string functions can still fail to work in the block.
• Because message bodies can be large, defining xxfi_body()
significantly impacts the filter performance.
• The filter application represents end-of-lines as received from the
SMTP transaction (normally as CR or LF).
• Later filter applications observe body changes made by earlier filter
applications.
• You can send message bodies in multiple portions with one call to
xxfi_body() per portion.
Arguments
You must call xxfi_body() with the following arguments:
ctx Specifies an opaque context structure.