qmail-smtpd.c

linux下qmail的源码 本人加了一些注释

//	qmail-smtpd接受远程主机的邮件并转交给队列处理程序qmail-queue来处理
//	由tcp-env.c启动,完成邮件smtp命令的接收，并调用相应的处理程序
//	只接收邮件内容(mailfrom,mailto)并传送给qmail-queue,并不对邮件进行转发

#include "sig.h"
#include "readwrite.h"
#include "stralloc.h"
#include "substdio.h"
#include "alloc.h"
#include "auto_qmail.h"
#include "control.h"
#include "received.h"
#include "constmap.h"
#include "error.h"
#include "ipme.h"
#include "ip.h"
#include "qmail.h"
#include "str.h"
#include "fmt.h"
#include "scan.h"
#include "byte.h"
#include "case.h"
#include "env.h"
#include "now.h"
#include "exit.h"
#include "rcpthosts.h"
#include "timeoutread.h"
#include "timeoutwrite.h"
#include "commands.h"

#define MAXHOPS 100
unsigned int databytes = 0;		//邮件最大长度：0=无限
int timeout = 1200;		//默认超时20分钟

//	向网络写，超时值为control/timeoutsmtpd指定的值，没有这个文件则取默认值20分钟
int safewrite(fd,buf,len) int fd; char *buf; int len;
{
  int r;
  r = timeoutwrite(timeout,fd,buf,len);
  if (r <= 0) _exit(1);
  return r;
}

char ssoutbuf[512];
substdio ssout = SUBSTDIO_FDBUF(safewrite,1,ssoutbuf,sizeof ssoutbuf);

void flush() { substdio_flush(&ssout); }

//	void out(s) char *s 相当于 void out(char* s)
void out(s) char *s; { substdio_puts(&ssout,s); }

//	错误处理函数
void die_read() { _exit(1); }
void die_alarm() { out("451 timeout (#4.4.2)\r\n"); flush(); _exit(1); }
void die_nomem() { out("421 out of memory (#4.3.0)\r\n"); flush(); _exit(1); }
void die_control() { out("421 unable to read controls (#4.3.0)\r\n"); flush(); _exit(1); }
void die_ipme() { out("421 unable to figure out my IP addresses (#4.3.0)\r\n"); flush(); _exit(1); }
void straynewline() { out("451 See http://pobox.com/~djb/docs/smtplf.html.\r\n"); flush(); _exit(1); }

void err_bmf() { out("553 sorry, your envelope sender is in my badmailfrom list (#5.7.1)\r\n"); }
void err_nogateway() { out("553 sorry, that domain isn't in my list of allowed rcpthosts (#5.7.1)\r\n"); }
void err_unimpl() { out("502 unimplemented (#5.5.1)\r\n"); }
void err_syntax() { out("555 syntax error (#5.5.4)\r\n"); }
void err_wantmail() { out("503 MAIL first (#5.5.1)\r\n"); }
void err_wantrcpt() { out("503 RCPT first (#5.5.1)\r\n"); }
void err_noop() { out("250 ok\r\n"); }
void err_vrfy() { out("252 send some mail, i'll try my best\r\n"); }
void err_qqt() { out("451 qqt failure (#4.3.0)\r\n"); }


stralloc greeting = {0};//end 错误处理函数

//	输出提示信息*code
void smtp_greet(code) char *code;
{
  substdio_puts(&ssout,code);
  substdio_put(&ssout,greeting.s,greeting.len);
}
void smtp_help()
{
  out("214 qmail home page: http://pobox.com/~djb/qmail.html\r\n");
}
void smtp_quit()
{
  smtp_greet("221 "); out("\r\n"); flush(); _exit(0);
}

char *remoteip;	//远端ip地址
char *remotehost;	//远端主机名
char *remoteinfo;	//远端信息
char *local;	//本地主机
char *relayclient;	//是否检查rcpthosts文件

stralloc helohost = {0};
char *fakehelo; /* pointer into helohost, or 0 */

void dohelo(arg) char *arg; {
  if (!stralloc_copys(&helohost,arg)) die_nomem(); 
  if (!stralloc_0(&helohost)) die_nomem(); 

  //fakehelo变量，如果helo参数指定的主机名与TCPREMOTEHOST环境变量中的主机名不同则
  //fakehelo的值为helo命令的参数指定的主机名。如果两者相同则fekehelo为NULL；
  //data命令处理程式用到这个变量
  fakehelo = case_diffs(remotehost,helohost.s) ? helohost.s : 0;
}

int liphostok = 0;
stralloc liphost = {0};
int bmfok = 0;

//	badmailfrom 用来指定不喜欢的发见人的邮件地址或者是域名
//该地址给主机发送邮件时将得到code 553，告知其是不受欢迎的发件人
stralloc bmf = {0};		
struct constmap mapbmf;

void setup()
{
  char *x;
  unsigned long u;
 
  if (control_init() == -1) die_control();	//control/me

  //读入欢迎信息greeting，如果不存在则从me文件复制
  if (control_rldef(&greeting,"control/smtpgreeting",1,(char *) 0) != 1)
    die_control();

  //读入localiphost，如果文件不存在则从me文件复制
  liphostok = control_rldef(&liphost,"control/localiphost",1,(char *) 0);
  if (liphostok == -1) die_control();

  //读control/timeoutsmtpd存入timeout,用于控制超时的情况
  if (control_readint(&timeout,"control/timeoutsmtpd") == -1) die_control();
  if (timeout <= 0) timeout = 1;

  if (rcpthosts_init() == -1) die_control();

  //读入badmailfrom文件存入bmf
  bmfok = control_readfile(&bmf,"control/badmailfrom",0);
  if (bmfok == -1) die_control();
  if (bmfok)
    if (!constmap_init(&mapbmf,bmf.s,bmf.len,0)) die_nomem();
 
  //读入databytes文件存入databytes，如果该文件不存在，则将databytes的值设为0.
  if (control_readint(&databytes,"control/databytes") == -1) die_control();
  x = env_get("DATABYTES");
  if (x) { scan_ulong(x,&u); databytes = u; }
  if (!(databytes + 1)) --databytes;
 
  //取tcp-environ环境变量，如果环境变量没有设置，将它的值设置为unknow
  //这些信息在tcp-env文件中
  remoteip = env_get("TCPREMOTEIP");
  if (!remoteip) remoteip = "unknown";
  local = env_get("TCPLOCALHOST");
  if (!local) local = env_get("TCPLOCALIP");
  if (!local) local = "unknown";
  remotehost = env_get("TCPREMOTEHOST");
  if (!remotehost) remotehost = "unknown";
  remoteinfo = env_get("TCPREMOTEINFO");

  //从环境变量RELAYCLIENT读入，如果RELAYCLIENT变量没有设置那么relayclient将会是NULL
  relayclient = env_get("RELAYCLIENT");
  dohelo(remotehost);
}


stralloc addr = {0}; /* will be 0-terminated, if addrparse returns 1 */

//对命令参数arg进行邮件地址分析，并将分离出的email地址存入全局缓存addr，成功返回值1，
//失败返回0
int addrparse(arg)
char *arg;
{
  int i;
  char ch;
  char terminator;
  struct ip_address ip;
  int flagesc;
  int flagquoted;
 
  //分离出邮件地址，例如：arg="",或arg=": [e-mail]"
  //执行下面这段程序后arg="[e-mail]"
  terminator = '>';
  i = str_chr(arg,'<');
  if (arg[i])
    arg += i + 1;
  else { /* partner should go read rfc 821 */
    terminator = ' ';
    arg += str_chr(arg,':');
    if (*arg == ':') ++arg;
    while (*arg == ' ') ++arg;
  }

  /* strip source route */
  if (*arg == '@') while (*arg) if (*arg++ == ':') break;

  if (!stralloc_copys(&addr,"")) die_nomem();
  flagesc = 0;
  flagquoted = 0;
  for (i = 0;ch = arg[i];++i) { /* copy arg to addr, stripping quotes */
    if (flagesc) {
      if (!stralloc_append(&addr,&ch)) die_nomem();
      flagesc = 0;
    }
    else {
      if (!flagquoted && (ch == terminator)) break;
      switch(ch) {
        case '\\': flagesc = 1; break;
        case '"': flagquoted = !flagquoted; break;
        default: if (!stralloc_append(&addr,&ch)) die_nomem();
      }
    }
  }
  /* could check for termination failure here, but why bother? */
  if (!stralloc_append(&addr,"")) die_nomem();

  //将ip地址转换为主机名：
  //如test@[10.0.6.21]转换为[e-mail]
  //依据是control/localiphost文件中有host.mydomain.org
  if (liphostok) {
    i = byte_rchr(addr.s,addr.len,'@');
    if (i < addr.len) /* if not, partner should go read rfc 821 */
      if (addr.s[i + 1] == '[')		//比较是否是用[]括起来的ip地址
        if (!addr.s[i + 1 + ip_scanbracket(addr.s + i + 1,&ip)])
          if (ipme_is(&ip)) {
            addr.len = i + 1;
            if (!stralloc_cat(&addr,&liphost)) die_nomem();
            if (!stralloc_0(&addr)) die_nomem();
          }
  }

  if (addr.len > 900) return 0;		//地址太长，出错返回
  return 1;		//成功返回
}

//简单的垃圾邮件检查，检查全局缓冲区addr中的地址是否有在badmailfrom中定义，如果
//有则返回1，否则返回0.
int bmfcheck()
{
  int j;
  if (!bmfok) return 0;
  if (constmap(&mapbmf,addr.s,addr.len - 1)) return 1;
  j = byte_rchr(addr.s,addr.len,'@');
  if (j < addr.len)
    if (constmap(&mapbmf,addr.s + j,addr.len - j - 1)) return 1;
  return 0;
}

//检查全局缓存addr中的邮件地址是否要进行转发(依据control/rcpthosts文件)
//可以进行转发返回1，拒绝转发返回0
int addrallowed()
{
  int r;