Fixed trailer construction with limit on FreeBSD and macOS. The ngx_chain_coalesce_file() function may produce more bytes to send then requested in the limit passed, as it aligns the last file position to send to memory page boundary. As a result, (limit - send) may become negative. This resulted in big positive number when converted to size_t while calling ngx_output_chain_to_iovec(). Another part of the problem is in ngx_chain_coalesce_file(): it changes cl to the next chain link even if the current buffer is only partially sent due to limit. Therefore, if a file buffer was not expected to be fully sent due to limit, and was followed by a memory buffer, nginx called sendfile() with a part of the file buffer, and the memory buffer in trailer. If there were enough room in the socket buffer, this resulted in a part of the file buffer being skipped, and corresponding part of the memory buffer sent instead. The bug was introduced in 8e903522c17a (1.7.8). Configurations affected are ones using limits, that is, limit_rate and/or sendfile_max_chunk, and memory buffers after file ones (may happen when using subrequests or with proxying with disk buffering). Fix is to explicitly check if (send < limit) before constructing trailer with ngx_output_chain_to_iovec(). Additionally, ngx_chain_coalesce_file() was modified to preserve unfinished file buffers in cl.

/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


#ifndef _NGX_MAIL_SMTP_MODULE_H_INCLUDED_
#define _NGX_MAIL_SMTP_MODULE_H_INCLUDED_


#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_mail.h>
#include <ngx_mail_smtp_module.h>


typedef struct {
    ngx_msec_t   greeting_delay;

    size_t       client_buffer_size;

    ngx_str_t    capability;
    ngx_str_t    starttls_capability;
    ngx_str_t    starttls_only_capability;

    ngx_str_t    server_name;
    ngx_str_t    greeting;

    ngx_uint_t   auth_methods;

    ngx_array_t  capabilities;
} ngx_mail_smtp_srv_conf_t;


void ngx_mail_smtp_init_session(ngx_mail_session_t *s, ngx_connection_t *c);
void ngx_mail_smtp_init_protocol(ngx_event_t *rev);
void ngx_mail_smtp_auth_state(ngx_event_t *rev);
ngx_int_t ngx_mail_smtp_parse_command(ngx_mail_session_t *s);


extern ngx_module_t  ngx_mail_smtp_module;


#endif /* _NGX_MAIL_SMTP_MODULE_H_INCLUDED_ */