smfi_chgheader()(3N)

NAME

smfi_chgheader() — changes or deletes a sendmail message header

#include <libmilter/mfapi.h> 

int smfi_chgheader( 
    SMFICTX *ctx,
    char *headerf,
    mi_int32 hdridx,
    char *headerv
 ); 

ctx: Specifies the opaque context structure.
headerf: Specifies the header name, which is a non-NULL, null-terminated string.
hdridx: Specifies the header index value (1-based). A hdridx value of 1 modifies the first occurrence of a header named headerf. If hdridx is greater than the number of times headerf appears, a new copy of headerf is added.

smfi_chgheader() changes the value of a header for the current message. smfi_chgheader() can be called only from the xxfi_eom() routine.

While smfi_chgheader() can be used to add new headers, it is more efficient to use smfi_addheader().
A filter that calls smfi_chgheader() must set the SMFIF_CHGHDRS flag in the smfiDesc_str structure passed to smfi_register().
The filter order is important for smfi_chgheader(). Filter placed later in the sequence will observer the changes already done by earlier filters.
The name and the value of the header are not checked for standards compliance. However, each line of the header must be under 2048 characters. If longer headers are needed, multi-line header must be used. To make a multi-line header, insert a linefeed (ASCII 0x0a, or \n in C) followed by at least one whitespace character, such as, a space (ASCII 0x20) or tab (ASCII 0x09, or \t in C). The linefeed must not be preceded by a carriage return (ASCII 0x0d); the MTA adds this automatically. It is the responsibility of the filter writer to ensure that standards are not violated.

smfi_chgheader() returns MI_FAILURE due to the following reasons:

smfi_chgheader() returns MI_SUCCESS on success.

int ret; 
  SMFICTX *ctx; 

  ... 

  ret = smfi_chgheader(ctx, "Content-Type", 1, 
        "multipart/mixed;\n\tboundary='foobar'"); 

smfi_chgheader() was developed by the Sendmail Inc.