qmail-queue.c

linux下qmail的源码 本人加了一些注释

//程序主要完成的功能是：
//1.生成自己的邮件首部，也就是你在邮件头中见到的类似下面的东西
//Recevied (qmail 855 invoked by uid 0); 2 May 2003 12:18:09 -0000
//2.建立3个文件	
//	queue/mess		邮件正文
//	queue/intd		用户id，进程id，mailform，rcptto
//	queue/todo		是intd目录下文件的复本
//3.写命名管道lock/trigger通知新邮件

#include <sys/types.h>
#include <sys/stat.h>
#include "readwrite.h"
#include "sig.h"
#include "exit.h"
#include "open.h"
#include "seek.h"
#include "fmt.h"
#include "alloc.h"
#include "substdio.h"
#include "datetime.h"
#include "now.h"
#include "triggerpull.h"
#include "extra.h"
#include "auto_qmail.h"
#include "auto_uids.h"
#include "date822fmt.h"
#include "fmtqfn.h"

#define DEATH 86400 /* 24 hours; _must_ be below q-s's OSSIFIED (36 hours) */
#define ADDR 1003

char inbuf[2048];
struct substdio ssin;
char outbuf[256];
struct substdio ssout;

datetime_sec starttime;
struct datetime dt;
unsigned long mypid;
unsigned long uid;
char *pidfn;
struct stat pidst;
unsigned long messnum;
char *messfn;
char *todofn;
char *intdfn;
int messfd;
int intdfd;
int flagmademess = 0;
int flagmadeintd = 0;

//	错误清理
void cleanup()
{
 if (flagmadeintd)
  {
   seek_trunc(intdfd,0);
   if (unlink(intdfn) == -1) return;
  }
 if (flagmademess)
  {
   seek_trunc(messfd,0);
   if (unlink(messfn) == -1) return;
  }
}

void die(e) int e; { _exit(e); }
void die_write() { cleanup(); die(53); }
void die_read() { cleanup(); die(54); }
void sigalrm() { /* thou shalt not clean up here */ die(52); }
void sigbug() { die(81); }

unsigned int receivedlen;
char *received;
/* "Received: (qmail-queue invoked by alias); 26 Sep 1995 04:46:54 -0000\n" */

static unsigned int receivedfmt(s)
char *s;
{
 unsigned int i;
 unsigned int len;
 len = 0;

 //生成		26 Sep 1995 04:46:54 -0000	的形式
 i = fmt_str(s,"Received: (qmail "); len += i; if (s) s += i;
 i = fmt_ulong(s,mypid); len += i; if (s) s += i;
 i = fmt_str(s," invoked "); len += i; if (s) s += i;
 if (uid == auto_uida)
  { i = fmt_str(s,"by alias"); len += i; if (s) s += i; }
 else if (uid == auto_uidd)
  { i = fmt_str(s,"from network"); len += i; if (s) s += i; }
 else if (uid == auto_uids)
  { i = fmt_str(s,"for bounce"); len += i; if (s) s += i; }
 else
  {
   i = fmt_str(s,"by uid "); len += i; if (s) s += i;
   i = fmt_ulong(s,uid); len += i; if (s) s += i;
  }
 i = fmt_str(s,"); "); len += i; if (s) s += i;
 i = date822fmt(s,&dt); len += i; if (s) s += i;
 return len;
}

void received_setup()
{
 receivedlen = receivedfmt((char *) 0);
 received = alloc(receivedlen + 1);
 if (!received) die(51);
 receivedfmt(received);
}

unsigned int pidfmt(s,seq)
char *s;
unsigned long seq;
{
 unsigned int i;
 unsigned int len;

 //生成类型pid/3434.34242424.1的字符串到s中
 //这个字符串实际上就是/var/qmail/queue/pid目录下一个文件名，指示当前进程的pid
 len = 0;
 i = fmt_str(s,"pid/"); len += i; if (s) s += i;
 i = fmt_ulong(s,mypid); len += i; if (s) s += i;
 i = fmt_str(s,"."); len += i; if (s) s += i;
 i = fmt_ulong(s,starttime); len += i; if (s) s += i;
 i = fmt_str(s,"."); len += i; if (s) s += i;
 i = fmt_ulong(s,seq); len += i; if (s) s += i;
 ++len; if (s) *s++ = 0;

 return len;
}

char *fnnum(dirslash,flagsplit)
char *dirslash;
int flagsplit;
{
 char *s;

 s = alloc(fmtqfn((char *) 0,dirslash,messnum,flagsplit));
 if (!s) die(51);
 fmtqfn(s,dirslash,messnum,flagsplit);
 return s;
}

//建立类似/var/run/inet.pid之类的进程id文件
void pidopen()
{
 unsigned int len;
 unsigned long seq;

 seq = 1;
 len = pidfmt((char *) 0,seq);
 pidfn = alloc(len);
 if (!pidfn) die(51);

 for (seq = 1;seq < 10;++seq)
  {
   if (pidfmt((char *) 0,seq) > len) die(81); /* paranoia */
   pidfmt(pidfn,seq);
   messfd = open_excl(pidfn);
   if (messfd != -1) return;
  }

 die(63);
}

char tmp[FMT_ULONG];

void main()
{
 unsigned int len;
 char ch;

 sig_blocknone();
 umask(033);
 if (chdir(auto_qmail) == -1) die(61);
 if (chdir("queue") == -1) die(62);		//改变工作目录到/var/qmail/queue

 mypid = getpid();
 uid = getuid();
 starttime = now();

 datetime_tai(&dt,starttime);	 //将起始时间转换为可读年月日时分秒的形式

 //生成自己的邮件头存入缓存reseived中
 //例如：received="Received:(qmail 3434 invoked by 34434); Apr 27 2003 14:55:34"
 received_setup();

 sig_pipeignore();
 sig_miscignore();
 sig_alarmcatch(sigalrm);	//捕捉alarm信号，控制超时
 sig_bugcatch(sigbug);

 alarm(DEATH);		//超时秒数，缺省值是86400(24小时)后错误返回52

 pidopen();		//建立进程id文件
 if (fstat(messfd,&pidst) == -1) die(63);

 messnum = pidst.st_ino;	//进程id文件的inode节点号

 /*生成将要建立的文件的文件名
	几个文件都是根据刚才建立的pid文件的inode节点号命名的.inode不可能被两个文件同时
	占用，这保证了邮件唯一性。其中mess目录下的文件放置有一个%23的问题，
　　tips: 因为是%23所以该目录名最大的可能只有22，明白queue/mess目录下目录为什么
	最大只22了吧 ，比如说inode节点号为3455,那么3455%23=5,
	那么将生成/var/qmail/queue/mess/5/3455 这样一个文件来存放邮件。
　	/var/qmail/queue/todo/3455与/var/qmail/queue/intd/3455是相同的,
	都是保存用户id,进程id,mailfrom,rcptto的。
 */
 messfn = fnnum("mess/",1);
 todofn = fnnum("todo/",0);
 intdfn = fnnum("intd/",0);

 if (link(pidfn,messfn) == -1) die(64);
 if (unlink(pidfn) == -1) die(63);

 //进程id文件使命很快结束,死掉了
 //所以你不应该想在queue/pid目录中找到进程id文件
 //另外，qmail-clean也将第七清理queue/pid目录下的pid文件，说定期其实也不是，
 //qmail-clean会在每收到30个清理邮件的请求后清理pid目录一次，这在分析qmail-clean
 //时我们将会看到
 flagmademess = 1;

 //fd1关联写mess/下新建的文件,通过管道连接<------qmail-smtp的qqt->fde
 //也就是说qmail-smtpd进程写它的qqt-fde，那就相当于写mess/下新建立的邮件
 //注意是关联不是正式写
 substdio_fdbuf(&ssout,write,messfd,outbuf,sizeof(outbuf));

 //fd0关联到读标准输入到缓存区inbuf通过管道连接<-----qmail-smtp的qqt->fdm
 //也就是说读ssin将从qmail-smtpd的qqt->fdm端读
 substdio_fdbuf(&ssin,read,0,inbuf,sizeof(inbuf));

 //向mess/下的邮件文件写qmail-queue的头部信息
 if (substdio_bput(&ssout,received,receivedlen) == -1) die_write();

 //从fd1读smtpd设置的邮件首部
 switch(substdio_copy(&ssout,&ssin))
  {
   case -2: die_read();
   case -3: die_write();
  }

 if (substdio_flush(&ssout) == -1) die_write();
 if (fsync(messfd) == -1) die_write();

 intdfd = open_excl(intdfn);
 if (intdfd == -1) die(65);
 flagmadeintd = 1;

 //fd1关联到写intd/下新建立的文件 fd0关联到读inbuff缓冲区
 substdio_fdbuf(&ssout,write,intdfd,outbuf,sizeof(outbuf));
 substdio_fdbuf(&ssin,read,1,inbuf,sizeof(inbuf));

 /*
　　向intd下新建立的文件写如下格式内容
　　这些内容来自于qmail-smtpd.c中的data命令的解释函数。
　　u[uid]p[pid]F[mailfrom]T[rcptto1][rcptto2][rcptton]
　　例如:[e-mail]向[e-mail]和[e-mail]发邮件可能会有如下内容
　　[e-mail]@[e-mail]
 */
 if (substdio_bput(&ssout,"u",1) == -1) die_write();
 if (substdio_bput(&ssout,tmp,fmt_ulong(tmp,uid)) == -1) die_write();
 if (substdio_bput(&ssout,"",1) == -1) die_write();

 if (substdio_bput(&ssout,"p",1) == -1) die_write();
 if (substdio_bput(&ssout,tmp,fmt_ulong(tmp,mypid)) == -1) die_write();
 if (substdio_bput(&ssout,"",1) == -1) die_write();

 if (substdio_get(&ssin,&ch,1) < 1) die_read();
 if (ch != 'F') die(91);
 if (substdio_bput(&ssout,&ch,1) == -1) die_write();
 for (len = 0;len < ADDR;++len)
  {
   if (substdio_get(&ssin,&ch,1) < 1) die_read();
   if (substdio_put(&ssout,&ch,1) == -1) die_write();
   if (!ch) break;
  }

 //如有多个邮件接收人时，这些接收人的地址总长度不能超过1023字节，如果每个
 //邮件地址约为15个字节的话，大约可能指定65个
 if (len >= ADDR) die(11);

 if (substdio_bput(&ssout,QUEUE_EXTRA,QUEUE_EXTRALEN) == -1) die_write();

 for (;;)
  {
   if (substdio_get(&ssin,&ch,1) < 1) die_read();
   if (!ch) break;
   if (ch != 'T') die(91);
   if (substdio_bput(&ssout,&ch,1) == -1) die_write();
   for (len = 0;len < ADDR;++len)
    {
     if (substdio_get(&ssin,&ch,1) < 1) die_read();
     if (substdio_bput(&ssout,&ch,1) == -1) die_write();
     if (!ch) break;
    }
   if (len >= ADDR) die(11);
  }

 if (substdio_flush(&ssout) == -1) die_write();
 if (fsync(intdfd) == -1) die_write();

 //复制intdfn到todofn 由此可见这两个是相同的文件
 if (link(intdfn,todofn) == -1) die(66);

 //向命名管道/var/qmail/queue/lock/trigger写一个字节(写的是0)，通知有新的邮件
 triggerpull();
 die(0);		//退出
}