程序员眼中的qmail(qmail源代码分析)

只为玩玩呱呱

只为玩玩呱呱

2016-02-19 21:35

下面是个程序员眼中的qmail(qmail源代码分析)教程,撑握了其技术要点,学起来就简单多了。赶紧跟着图老师小编一起来看看吧!
很多人对qmail smtp的认证机制,环境变量,执行顺序不太了解。  仔细看完这一大篇代码后相信你会明白很多你过去不太明白的问题。  当然你要有一点点c语言基础。也只要一点点。  Come from: ChongQing Gearbox co.,ltd  这份文件还不完善,假如您完善了它请发一份给我: beggar110@163.com  这份文件是给想深入了解qmail和想hacker qmail的人读的,假如你只是想建立一个能够运作的mail服务器,没有必要读下去了。它将浪费你很多的时间。  假如你对qmail控制文件还不是很了解,阅读这份文件之前,请先阅读rainbow的《qmail控制文件详解》  在这里你可以找到www.chinaunix.net/forum/viewtopic.php?t=1126  好的。开始我们qmail内部的漫游吧!!!Let's go!  代码:  qmail 总览  tcpserver MUA     V V  qmail-smtpd qmail-inject     +-----------qmail-queue-----------+      qmail-send    +------------+------------+     V V  qmail-rspawn qmail-lspawn     V V  qmail-remote qmail-local        V V  INTERNET ----qmail-pop3d      vchkpw      qmail-popup      tcpserver--+  qmail-smtpd.c源代码分析(去掉了所有include)  qmail -smtpd是由tcpserver或由tcp-env启动。tcpserver负责监听端口,假如指定了-x rule.cbd,tcpserver会先决断是断开连接还是启动qmail子进程。假如没有指定-x参数启动tcpserver,那么直接启动 qmail-smtpd.启动qmail-smtpd之前将来自网络的数据连接重定向到qmail-smtpd的fd0,fd1.还会初始化一些 qmail-smtpd需要的环境变量,如TCPREMOTEIP.  tcp-env只会初始化qmail-smtpd的环境变量,不负责监听端口及重定向网络连接。所以tcp-env要和inetd配合使用。当然,由于初始化环境变量的工作tcpserver也会作,所以没有必要tcpserver和tcp-env配合使用.  qmail-smtpd完成邮件smtp命令的接收,并调用相应的处理程序。  检查mail 中的地址是否在control/badmailfrom中定义(MAIL命令)  检查是否设置了RELAYCLIENT环境变量或 rcpt 中的地址是否是control/rcpthosts中定义(RCPT命令)  需要明确的是qmail-smtpd只是简单的接收邮件内容传送给qmail-queue,并不对邮件进行转发(DATA命令)。  当然还要向qmail-queue传送mailfrom,mailto  代码:  #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; { substdio_puts(&ssout,s); }  //错误处理函数  void die_read() { _exit(1); }  void die_alarm() { out("451 timeout (#4.4.2)"); flush(); _exit(1); }  void die_nomem() { out("421 out of memory (#4.3.0)"); flush(); _exit(1); }  void die_control() { out("421 unable to read controls (#4.3.0)"); flush(); _exit(1); }  void die_ipme() { out("421 unable to figure out my IP addresses (#4.3.0)"); flush(); _exit(1); }  void straynewline() { out("451 See pobox.com/~djb/docs/smtplf.Html."); flush(); _exit(1); }  void err_bmf() { out("553 sorry, your envelope sender is in my badmailfrom list (#5.7.1)"); }  void err_nogateway() { out("553 sorry, that domain isn't in my list of allowed rcpthosts (#5.7.1)"); }  void err_unimpl() { out("502 unimplemented (#5.5.1)"); }  void err_syntax() { out("555 syntax error (#5.5.4)"); }  void err_wantmail() { out("503 MAIL first (#5.5.1)"); }  void err_wantrcpt() { out("503 RCPT first (#5.5.1)"); }  void err_noop() { out("250 ok"); }  void err_vrfy() { out("252 send some mail, i'll try my best"); }  void err_QQt() { out("451 qqt failure (#4.3.0)"); }  stralloc greeting = {0};  //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:   voidpobox.com/~djb/qmail.html");  }  void smtp_quit()  {  smtp_greet("221 "); out(""); 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,假如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.假如两者相同则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;  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,假如不存在则从me文件复制  if (control_rldef(&greeting,"control/smtpgreeting",1,(char *) 0) != 1)  die_control();  //读入localiphost,假如文件不存在则从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,假如该文件不存在,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,假如环境变量没有设置,将它的值设置为unknow.  //这些信息来自tcpserver,或tcp-env之类的程式  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.  //假如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  //成功返回值为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=": email@eg.org "  //执行下面这段程式后arg="email@eg.org"  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 test@host.mydomain.org  //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,  //假如有则返回 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;  r = rcpthosts(addr.s,str_len(addr.s));  if (r == -1) die_control();  return r;  }  int seenmail = 0;  int flagbarf; /* defined if seenmail */  stralloc mailfrom = {0};  stralloc rcptto = {0};  void smtp_helo(arg) char *arg;  {  smtp_greet("250 "); out("");  seenmail = 0; dohelo(arg);  }  void smtp_ehlo(arg) char *arg;  {  smtp_greet("250-"); out("250-PIPELINING250 8BITMIME");  seenmail = 0; dohelo(arg);  }  //重新初始化  //调用helo或ehlo命令都会完成相同的功能  void smtp_rset()  {  seenmail = 0;  out("250 flushed");  }  //mail命令解释程式. 重要变量: [mailfrom /全局]  //该函数完成检查mailfrom是否在badmailfrom中定义  //设置标志指明mail命令已经执行  void smtp_mail(arg) char *arg;  {  if (!addrparse(arg)) { err_syntax(); return; }  flagbarf = bmfcheck(); //检查是否badmailfrom,假如是设置相应标志,这个标志在rcpt命令的处理程式中才起作用  seenmail = 1;//指示已经执行过mail命令.  if (!stralloc_copys(&rcptto,"")) die_nomem();//分配rcptto缓冲区  if (!stralloc_copys(&mailfrom,addr.s)) die_nomem();//复制mail命令中指定的地址到mailfrom  if (!stralloc_0(&mailfrom)) die_nomem();  out("250 ok");  }  //rcpt命令解释程式. 重要变量: [ rcptto /全局]  void smtp_rcpt(arg) char *arg; {  if (!seenmail) { err_wantmail(); return; }//mail命令是否已执行?  if (!addrparse(arg)) { err_syntax(); return; }//分离邮件地址参数存入全局缓存addr  if (flagbarf) { err_bmf(); return; }//假如mail命令中的地址在control/badmailfrom中有定义,返回  //至此addr缓存中包含了rcpt命令指定的email地址.  //假如rcpt 命令,则有addr="email@eg.org".这个变量是在addrparse函数中符值的  //假如 RELAYCLIENT 环境变量设置将不进行rcpthosts,morercpthosts.cdb的比较  //注重,打过smtp认证补丁,假如通过认证后会设置relayclient=""  if (relayclient) {  --addr.len;  if (!stralloc_cats(&addr,relayclient)) die_nomem();  if (!stralloc_0(&addr)) die_nomem();  }  else//假如没有指定RELAYCLIENT变量,则由control/rcpthosts决定是否进行转发  if (!addrallowed()) { err_nogateway(); return; }  //生成头连接到全局缓存rcptto:  //例如地址'rcpt test@eg.org' 命令将产生 rcptto="Temail@eg.org"  //多次执行rcpt命令效果会是rcptto="Ttest@eg.orgTtwo@eg.org"  if (!stralloc_cats(&rcptto,"T")) die_nomem();  if (!stralloc_cats(&rcptto,addr.s)) die_nomem();  if (!stralloc_0(&rcptto)) die_nomem();  out("250 ok");  }  //saferead,从网络读len个字节到buf缓冲区  //返回实际读到的字节数.  //超时值为control/timeoutsmtpd文件中指定的值。见setup()函数.(默认值1200秒)  int saferead(fd,buf,len) int fd; char *buf; int len;  {  int r;  flush();  r = timeoutread(timeout,fd,buf,len);  if (r == -1) if (errno == error_timeout) die_alarm();  if (r = 0) die_read();  return r;  }  char ssinbuf[1024];  substdio ssin = SUBSTDIO_FDBUF(saferead,0,ssinbuf,sizeof ssinbuf);  struct qmail qqt;  unsigned int bytestooverflow = 0;  void put(ch)  char *ch;  {  if (bytestooverflow)  if (!--bytestooverflow)  qmail_fail(&qqt);  qmail_put(&qqt,ch,1);  }  void blast(hops)  int *hops;  {  char ch;  int state;  int flaginheader;  int pos; /* number of bytes since most recent , if fih */  int flagmaybex; /* 1 if this line might match RECEIVED, if fih */  int flagmaybey; /* 1 if this line might match , if fih */  int flagmaybez; /* 1 if this line might match DELIVERED, if fih */  state = 1;  *hops = 0;  flaginheader = 1;  pos = 0; flagmaybex = flagmaybey = flagmaybez = 1;  for (;;) {  substdio_get(&ssin,&ch,1);//从标准输入(也就是网络)读邮件内容直到读到仅有一个点的行.  if (flaginheader) {  if (pos 9) {  if (ch != "delivered"[pos]) if (ch != "DELIVERED"[pos]) flagmaybez = 0;  if (flagmaybez) if (pos == 8) ++*hops;  if (pos 8)  if (ch != "received"[pos]) if (ch != "RECEIVED"[pos]) flagmaybex = 0;  if (flagmaybex) if (pos == 7) ++*hops;  if (pos 2) if (ch != ""[pos]) flagmaybey = 0;  if (flagmaybey) if (pos == 1) flaginheader = 0;  }  ++pos;  if (ch == '') { pos = 0; flagmaybex = flagmaybey = flagmaybez = 1; }  }  switch(state) {  case 0:  if (ch == '') straynewline();  if (ch == '') { state = 4; continue; }  break;  case 1: /* */  if (ch == '') straynewline();  if (ch == '.') { state = 2; continue; }  if (ch == '') { state = 4; continue; }  state = 0;  break;  case 2: /* + . */  if (ch == '') straynewline();  if (ch == '') { state = 3; continue; }  state = 0;  break;  case 3: /* + . */  if (ch == '') return;  put(".");  put("");  if (ch == '') { state = 4; continue; }  state = 0;  break;  case 4: /* + */  if (ch == '') { state = 1; break; }  if (ch != '') { put(""); state = 0; }  }  put(&ch);  }  }  char accept_buf[FMT_ULONG];  void acceptmessage(qp) unsigned long qp;  {  datetime_sec when;  when = now();  out("250 ok ");  accept_buf[fmt_ulong(accept_buf,(unsigned long) when)] = 0;  out(accept_buf);  out(" qp ");  accept_buf[fmt_ulong(accept_buf,qp)] = 0;  out(accept_buf);  out("");  }  //data 命令解释程式  //完成向qmail-queue投递邮件  void smtp_data() {  int hops;  unsigned long qp;  char *qqx;  if (!seenmail) { err_wantmail(); return; } //假如没有执行过mail命令,出错返回  if (!rcptto.len) { err_wantrcpt(); return; } //假如没有执行rcpt命令,出错返回  seenmail = 0; //将mail命令标志失效,  //databytes 邮件最大长度,假如没有指定那么它的值将是0  if (databytes) bytestooverflow = databytes + 1;  if (qmail_open(&qqt) == -1) { err_qqt(); return; }//建立子进程执行qmail-queue  qp = qmail_qp(&qqt); //qp 为qmail-queue process缩写,it's a process id.  out("354 go ahead");  //向新建立的进程传送邮件头  received(&qqt,"SMTP",local,remoteip,remotehost,remoteinfo,fakehelo);  blast(&hops);  hops = (hops = MAXHOPS);  if (hops) qmail_fail(&qqt);  //向qmail-queue传送邮件头信息.  //假如hong@hg.org 向 lyx@hg.org发送邮件,那么向qmail-queue传送的字符串将是  // Fhong@hg.orgTlyx@hg.org  qmail_from(&qqt,mailfrom.s);  qmail_put(&qqt,rcptto.s,rcptto.len);  qqx = qmail_close(&qqt);  if (!*qqx) { acceptmessage(qp); return; }//假如接收成功  if (hops) { out("554 too many hops, this message is looping (#5.4.6)"); return; }  if (databytes) if (!bytestooverflow) { out("552 sorry, that message size exceeds my databytes limit (#5.3.4)"); return; }  if (*qqx == 'D') out("554 "); else out("451 ");  out(qqx + 1);  out("");  }  //smtp命令处理函数表  struct commands smtpcommands[] = {  { "rcpt", smtp_rcpt, 0 }  , { "mail", smtp_mail, 0 }  , { "data", smtp_data, flush } //建立子进程执行qamil-queue,并向其传送邮件.  , { "quit", smtp_quit, flush }  , { "helo", smtp_helo, flush }  , { "ehlo", smtp_ehlo, flush }  , { "rset", smtp_rset, 0 }  , { "help", smtp_help, flush }  , { "noop", err_noop, flush } //实际上未实现的命令, { "vrfy", err_vrfy, flush } //实际上未实现的命令, { 0, err_unimpl, flush } //命令错误  } ;  /*  qmail-smtpd 是由tcpserver,或tcp-env之类的程式启动  tcpserver,tcp-env将来自网络的连接重定向到qmail-smtpd的标准输入及标准输出.这些程式建立一些环境变量(如TCPREMOTEHOST,TCPREMOTEIP)将由setup()函数使用  */  void main()  {  sig_pipeignore();//忽略信号.  if (chdir(auto_qmail) == -1) die_control();//改变当前目录到 /var/qmail.  setup();//读控制文件及相应的环境变量.  if (ipme_init() != 1) die_ipme(); //取本地接口的IP地址:  smtp_greet("220 "); //显示欢迎信息.  out(" ESMTP");  //从标准输入(网络连接)读入smtp命令.  if (commands(&ssin,&smtpcommands) == 0) die_read();  die_nomem();  }  ==完==  qmail-queue源代码分析  Programmer:夜未眠  Comefrom:ChongQing Gearbox co.,ltd  程序主要完成的功能是:  1.生成自已的邮件首部,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,mailfrom,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  代码:  #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;  static unsigned int receivedfmt(s)  char *s;  {  unsigned int i;  unsigned int len;  len = 0;  /*生成  /* "Received: (qmail-queue invoked by alias); 26 Sep 1995 04:46:54 -0000" */  [日 月 年 时 分 秒]  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;  }  void pidopen() //建立类似/var/run/inet.pid之类的进程id文件.  {  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  //生成自已的邮件头存入缓存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); //解释为message file name  todofn = fnnum("todo/",0); //todo file name  intdfn = fnnum("intd/",0); //intd file name  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也将定期清理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关联到写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  //注重是关联不是正式写  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:lyx@hg.org向hong@hg.org和beggar@hg.org发邮件可能会有如下内容  u6027p34234Flyx@hg.orgThong@hg.orgTbeggar@hg.org  */  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不长度不能超过1023字节,假如每个邮件地址约为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);  triggerpull(); //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  die(0); //退出  }  ==完==  qmail-popup.c分析  Programmer:夜未眠  Come from:ChongQing Gearbox co.,ltd  qmail -popup也是由tcpserver或tcp-env之类的程式启动。这些程式是通过管道与qmail-popup通信的。这也是qmail 的美妙之处,总观整个qmail源代码,除少量dns代码外。基本上没有使用网络编程。各个进程间大部分都是通管道通信。把监听,读写网络部分交给 inetd或tcpserver来作。使得qmail代码相当轻易阅读理解。  主要功能:  1.从网络读pop3命令,进行相应处理。  2.调用子进程(vchkpw或checkpassWord,具体是哪一个由你在运行参数中指定,当然,仔细分析完doanddie函数后你也许就能编写自己的checkpw了,呵呵)完成检验密码,启动qmail-pop3d的工作  重要的函数是doanddie. 理解这个函数基本上就能理解qmail pop密码的检验流程。  几个程式间的关系是:  代码:  tcpserver----qmail-popup----vchkpw----认证成功---qmail-pop3d        ---------- 认证失败-----------+  ==========================  代码:  void die() { _exit(1); }  int saferead(fd,buf,len) int fd; char *buf; int len;  {  int r;  r = timeoutread(1200,fd,buf,len);  if (r = 0) die();  return r;  }  int safewrite(fd,buf,len) int fd; char *buf; int len;  {  int r;  r = timeoutwrite(1200,fd,buf,len);  if (r = 0) die();  return r;  }  char ssoutbuf[128];  substdio ssout = SUBSTDIO_FDBUF(safewrite,1,ssoutbuf,sizeof ssoutbuf);  char ssinbuf[128];  substdio ssin = SUBSTDIO_FDBUF(saferead,0,ssinbuf,sizeof ssinbuf);  void puts(s) char *s;  {  substdio_puts(&ssout,s);  }  void flush()  {  substdio_flush(&ssout);  }  void err(s) char *s;  {  puts("-ERR ");  puts(s);  puts("");  flush();  }  void die_usage() { err("usage: popup hostname subprogram"); die(); }  void die_nomem() { err("out of memory"); die(); }  void die_pipe() { err("unable to open pipe"); die(); }  void die_write() { err("unable to write pipe"); die(); }  void die_fork() { err("unable to fork"); die(); }  void die_childcrashed() { err("aack, child crashed"); }  void die_badauth() { err("authorization failed"); }  void err_syntax() { err("syntax error"); }  void err_wantuser() { err("USER first"); }  void err_authoriz() { err("authorization first"); }  void okay() { puts("+OK "); flush(); }  void pop3_quit() { okay(); die(); }  //FMT_ULONG 40 /* enough space to hold 2^128 - 1 in decimal, plus
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