Monday, December 6, 2010

Small is beautiful

How small can a web server be.



The smallest I could find in term of physical size is http://d116.com/ace/webACE: A Fairchild ACE1101MT8 microcontroller programmed as a Web server and containing two tiny web pages in its on-chip memory.

Going to the code side. There is the heavy weight Apache and the light weight Nginx and Lighttpd. Need a still smaller solution. Saw this implementation in IBM developers work. http://www.ibm.com/developerworks/systems/library/es-nweb/index.html


#include < stdio.h >
#include < stdlib.h >
#include < unistd.h >
#include < errno.h >
#include < string.h >
#include < fcntl.h >
#include < signal.h >
#include < sys/types.h >
#include < sys/socket.h >
#include < netinet/in.h >
#include < arpa/inet.h >

#define BUFSIZE 8096
#define ERROR 42
#define SORRY 43
#define LOG 44

struct {
char *ext;
char *filetype;
} extensions [] = {
{"gif", "image/gif" },
{"jpg", "image/jpeg"},
{"jpeg","image/jpeg"},
{"png", "image/png" },
{"zip", "image/zip" },
{"gz", "image/gz" },
{"tar", "image/tar" },
{"htm", "text/html" },
{"html","text/html" },
{0,0} };

void log(int type, char *s1, char *s2, int num)
{
int fd ;
char logbuffer[BUFSIZE*2];

switch (type) {
case ERROR: (void)sprintf(logbuffer,"ERROR: %s:%s Errno=%d exiting pid=%d",s1, s2, errno,getpid()); break;
case SORRY:
sprintf(logbuffer, "
nweb Web Server Sorry: %s %s
\r\n", s1, s2);
write(num,logbuffer,strlen(logbuffer));
sprintf(logbuffer,"SORRY: %s:%s",s1, s2);
break;
case LOG: (void)sprintf(logbuffer," INFO: %s:%s:%d",s1, s2,num); break;
}
/* no checks here, nothing can be done a failure anyway */
if((fd = open("nweb.log", O_CREAT| O_WRONLY | O_APPEND,0644)) >= 0) {
(void)write(fd,logbuffer,strlen(logbuffer));
(void)write(fd,"\n",1);
(void)close(fd);
}
if(type == ERROR || type == SORRY) exit(3);
}

/* this is a child web server process, so we can exit on errors */
void web(int fd, int hit)
{
int j, file_fd, buflen, len;
long i, ret;
char * fstr;
static char buffer[BUFSIZE+1]; /* static so zero filled */

ret =read(fd, buffer, BUFSIZE); /* read Web request in one go */
if(ret == 0 || ret == -1) { /* read failure stop now */
log(SORRY,"failed to read browser request","",fd);
}
if(ret > 0 && ret < BUFSIZE) /* return code is valid chars */
buffer[ret]=0; /* terminate the buffer */
else buffer[0]=0;

for(i=0 ; i < ret ; i++) /* remove CF and LF characters */
if(buffer[i] == '\r' || buffer[i] == '\n')
buffer[i]='*';
log(LOG,"request",buffer,hit);

if( strncmp(buffer, "GET ",4) && strncmp(buffer,"get ",4) )
log(SORRY,"Only simple GET operation supported",buffer,fd);

for(i=4 ; i < BUFSIZE; i++) { /* null terminate after the second space to ignore extra stuff */
if(buffer[i] == ' ') { /* string is "GET URL " +lots of other stuff */
buffer[i] = 0;
break;
}
}

for(j=0; j < i-1 ; j++) /* check for illegal parent directory use .. */
if(buffer[j] == '.' && buffer[j+1] == '.')
log(SORRY,"Parent directory (..) path names not supported",buffer,fd);

if( !strncmp(&buffer[0],"GET /\0",6) || !strncmp(&buffer[0],"get /\0",6) ) /* convert no filename to index file */
(void)strcpy(buffer,"GET /index.html");

/* work out the file type and check we support it */
buflen=strlen(buffer);
fstr = (char *)0;
for(i=0;extensions[i].ext != 0;i++) {
len = strlen(extensions[i].ext);
if( !strncmp(&buffer[buflen-len], extensions[i].ext, len)) {
fstr =extensions[i].filetype;
break;
}
}
if(fstr == 0) log(SORRY,"file extension type not supported",buffer,fd);

if(( file_fd = open(&buffer[5] , O_RDONLY)) == -1) /* open the file for reading */
log(SORRY, "failed to open file",&buffer[5],fd);

log(LOG,"SEND",&buffer[5],hit);

(void)sprintf(buffer,"HTTP/1.0 200 OK\r\nContent-Type: %s\r\n\r\n", fstr);
(void)write(fd,buffer,strlen(buffer));

/* send file in 8KB block - last block may be smaller */
while ( (ret = read(file_fd, buffer, BUFSIZE)) > 0 ) {
(void)write(fd,buffer,ret);
}
#ifdef LINUX
sleep(1); /* to allow socket to drain */
#endif
exit(1);
}


int main(int argc, char **argv)
{
int i, port, pid, listenfd, socketfd, hit;
size_t length;
static struct sockaddr_in cli_addr; /* static = initialised to zeros */
static struct sockaddr_in serv_addr; /* static = initialised to zeros */

if( argc < 3 || argc > 3 || !strcmp(argv[1], "-?") ) {
(void)printf("hint: nweb Port-Number Top-Directory\n\n"
"\tnweb is a small and very safe mini web server\n"
"\tnweb only servers out file/web pages with extensions named below\n"
"\t and only from the named directory or its sub-directories.\n"
"\tThere is no fancy features = safe and secure.\n\n"
"\tExample: nweb 8181 /home/nwebdir &\n\n"
"\tOnly Supports:");
for(i=0;extensions[i].ext != 0;i++)
(void)printf(" %s",extensions[i].ext);

(void)printf("\n\tNot Supported: URLs including \"..\", Java, Javascript, CGI\n"
"\tNot Supported: directories / /etc /bin /lib /tmp /usr /dev /sbin \n"
"\tNo warranty given or implied\n\tNigel Griffiths nag@uk.ibm.com\n"
);
exit(0);
}
if( !strncmp(argv[2],"/" ,2 ) || !strncmp(argv[2],"/etc", 5 ) ||
!strncmp(argv[2],"/bin",5 ) || !strncmp(argv[2],"/lib", 5 ) ||
!strncmp(argv[2],"/tmp",5 ) || !strncmp(argv[2],"/usr", 5 ) ||
!strncmp(argv[2],"/dev",5 ) || !strncmp(argv[2],"/sbin",6) ){
(void)printf("ERROR: Bad top directory %s, see nweb -?\n",argv[2]);
exit(3);
}
if(chdir(argv[2]) == -1){
(void)printf("ERROR: Can't Change to directory %s\n",argv[2]);
exit(4);
}

/* Become deamon + unstopable and no zombies children (= no wait()) */
if(fork() != 0)
return 0; /* parent returns OK to shell */
(void)signal(SIGCLD, SIG_IGN); /* ignore child death */
(void)signal(SIGHUP, SIG_IGN); /* ignore terminal hangups */
for(i=0;i<32;i++)
(void)close(i); /* close open files */
(void)setpgrp(); /* break away from process group */

log(LOG,"nweb starting",argv[1],getpid());
/* setup the network socket */
if((listenfd = socket(AF_INET, SOCK_STREAM,0)) <0)
log(ERROR, "system call","socket",0);
port = atoi(argv[1]);
if(port < 0 || port >60000)
log(ERROR,"Invalid port number (try 1->60000)",argv[1],0);
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
serv_addr.sin_port = htons(port);
if(bind(listenfd, (struct sockaddr *)&serv_addr,sizeof(serv_addr)) < 0)
log(ERROR,"system call","bind",0);
if( listen(listenfd,64) <0)
log(ERROR,"system call","listen",0);

for(hit=1; ;hit++) {
length = sizeof(cli_addr);
if((socketfd = accept(listenfd, (struct sockaddr *)&cli_addr, &length)) < 0)
log(ERROR,"system call","accept",0);

if((pid = fork()) < 0) {
log(ERROR,"system call","fork",0);
}
else {
if(pid == 0) { /* child */
(void)close(listenfd);
web(socketfd,hit); /* never returns */
} else { /* parent */
(void)close(socketfd);
}
}
}
}



A working server in 202 lines of pure C code. The compiled executable itself under 10kb size. Can it be reduced even smaller. not massive in terms of feature but still a good implementation for any one to learn from.

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