qmail-start.c

linux下qmail的源码 本人加了一些注释

//这是个很简单的程序，完成qmail-send，qmail-clean,qmail-lspawn,qmail-rspawn,splogger
//的启动，并通过管道将他们联系在一起，当然不是网状连接，具体如下
/*
	qmail-lspawn fd0 <-------	qmail-send fd1
	qmail-lspawn fd1 ------->	qmail-send fd2
	qmail-rspawn fd0 <-------	qmail-send fd3
	qmail-rspawn fd1 ------->	qmail-send fd4
	qmail-clean	 fd0 <-------	qmail-send fd5
	qmail-clean  fd1 ------->	qmail-send fd6

  理解他们之间的关系(注意方向)对于理解qmail-send源代码非常重要，仔细再看一次。
  因为其比较简单，所以这里就不对他的源代码作过细的分析：
*/

#include "fd.h"
#include "prot.h"
#include "exit.h"
#include "fork.h"
#include "auto_uids.h"

char *(qsargs[]) = { "qmail-send", 0 };
char *(qcargs[]) = { "qmail-clean", 0 };
char *(qlargs[]) = { "qmail-lspawn", "./Mailbox", 0 };
char *(qrargs[]) = { "qmail-rspawn", 0 };

void die() { _exit(111); }

int pi0[2];		//splogger qmail 
int pi1[2];		//qmail-lspawn fd0 <-------- qmail-send fd1
int pi2[2];		//qmail-lspawn fd1 --------> qmail-send fd2
int pi3[2];		//qmail-rspawn fd0 <-------- qmail-send fd3
int pi4[2];		//qmail-rspawn fd1 --------> qmail-send fd4
int pi5[2];		//qmail-clean fd0 <-------- qmail-send fd5
int pi6[2];		//qmail-clean fd1 --------> qmail-send fd6

void close23456() { close(2); close(3); close(4); close(5); close(6); }

//因为没有关闭pi0。所以所有的子进程都可以通过写pi0来记录maillog
void closepipes() {
  close(pi1[0]); close(pi1[1]); close(pi2[0]); close(pi2[1]);
  close(pi3[0]); close(pi3[1]); close(pi4[0]); close(pi4[1]);
  close(pi5[0]); close(pi5[1]); close(pi6[0]); close(pi6[1]);
}

void main(argc,argv)
int argc;
char **argv;
{
  if (chdir("/") == -1) die();
  umask(077);
  if (prot_gid(auto_gidq) == -1) die();

  if (fd_copy(2,0) == -1) die();
  if (fd_copy(3,0) == -1) die();
  if (fd_copy(4,0) == -1) die();
  if (fd_copy(5,0) == -1) die();
  if (fd_copy(6,0) == -1) die();

  if (argv[1]) {
    qlargs[1] = argv[1];
    ++argv;
  }

  if (argv[1]) {
    if (pipe(pi0) == -1) die();
    switch(fork()) {
      case -1:
	die();
      case 0:
        if (prot_gid(auto_gidn) == -1) die();
        if (prot_uid(auto_uidl) == -1) die();
        close(pi0[1]);
        if (fd_move(0,pi0[0]) == -1) die();		//重定向pi0[0]到splogger的fd0
        close23456();
        execvp(argv[1],argv + 1);	//启动splogger
	die();
    }
    close(pi0[0]);
    if (fd_move(1,pi0[1]) == -1) die();
  }
 
  if (pipe(pi1) == -1) die();
  if (pipe(pi2) == -1) die();
  if (pipe(pi3) == -1) die();
  if (pipe(pi4) == -1) die();
  if (pipe(pi5) == -1) die();
  if (pipe(pi6) == -1) die();
 
  switch(fork()) {		//启动qmail-lspawn
    case -1: die();
    case 0:
      if (fd_copy(0,pi1[0]) == -1) die();
      if (fd_copy(1,pi2[1]) == -1) die();
      close23456();
      closepipes();
      execvp(*qlargs,qlargs);
      die();
  }
 
  switch(fork()) {		//启动qmail-rspawn
    case -1: die();
    case 0:
      if (prot_uid(auto_uidr) == -1) die();
      if (fd_copy(0,pi3[0]) == -1) die();
      if (fd_copy(1,pi4[1]) == -1) die();
      close23456();
      closepipes();
      execvp(*qrargs,qrargs);
      die();
  }
 
  switch(fork()) {		//启动qmail-clean
    case -1: die();
    case 0:
      if (prot_uid(auto_uidq) == -1) die();
      if (fd_copy(0,pi5[0]) == -1) die();
      if (fd_copy(1,pi6[1]) == -1) die();
      close23456();
      closepipes();
      execvp(*qcargs,qcargs);
      die();
  }
 
  if (prot_uid(auto_uids) == -1) die();
  if (fd_copy(0,1) == -1) die();		//重定向管道，把qmail-send与上面个进程联系起来
  if (fd_copy(1,pi1[1]) == -1) die();
  if (fd_copy(2,pi2[0]) == -1) die();
  if (fd_copy(3,pi3[1]) == -1) die();
  if (fd_copy(4,pi4[0]) == -1) die();
  if (fd_copy(5,pi5[1]) == -1) die();
  if (fd_copy(6,pi6[0]) == -1) die();
  closepipes();
  execvp(*qsargs,qsargs);		//最后启动qmail-send
  die();
}