main.c

#define _GNU_SOURCE

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/sendfile.h>
#include <netinet/in.h>
#include <fcntl.h>
#include <sched.h>
#include <unistd.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>

#define THREADS 32
#define MAXWAIT 128
#define STACKSIZE 65536
#define FILESIZE (32000 * 65536)

struct thread {
  pid_t pid;
  int fd;
};

struct thread threads[THREADS];
int sockfd;
char *path;
int contentfd;

#define info (*((struct thread *) data))

int thr(void *data) {
  off_t zero;
  char req[4096];
  int len;
  char *nlnl;

  while (1) {
    info.fd = accept(sockfd, NULL, NULL);

    *(uint32_t *)req = 0;
    while((len = read(info.fd, req + 4, sizeof(req) - 8)) > 0) {
      for(nlnl = req; nlnl < req + len + 4; ++nlnl) {
        if(*(uint16_t *)nlnl == 0x0A0A) goto req_complete;
        if(*(uint32_t *)nlnl == 0x0A0D0A0Dul) goto req_complete;
      }
      *(uint32_t *)req = *(uint32_t *)(req + len);
    }

    req_complete:

    zero = 0;
    sendfile(info.fd, contentfd, &zero, FILESIZE);
    shutdown(info.fd, SHUT_WR);
    close(info.fd);
  }

  return 0;
}

void term(int no_use) {
  exit(0);
}

int main(int argc, char *argv[]) {
  struct sockaddr_in6 http_addr;
  int nt;
  char *stack;
  int yes = 1;
  int port;

  if((contentfd = open(path, O_RDONLY)) < 0) {
    fprintf(stderr, "could not open path to serve\n");
    exit(1);
  }

  if(setuid(65535) < 0) {
    fprintf(stderr, "setuid failed\n");
    return 1;
  }

  if(argc != 3) {
    fprintf(stderr, "Usage: sfhttpd <port> <file>\n");
    return 1;
  }

  if(sscanf(argv[1], "%d", &port) != 1) {
    fprintf(stderr, "Usage: sfhttpd <port> <file>\n");
    return 1;
  }

  path = argv[2];

  http_addr.sin6_family = AF_INET6;
  http_addr.sin6_port = htons(port);
  memcpy(&http_addr.sin6_addr.s6_addr, &in6addr_any, 16);
  
  if ((sockfd = socket(AF_INET6, SOCK_STREAM, IPPROTO_TCP)) < 0) {
    fprintf(stderr, "could not create socket\n");
    return 1;
  }

  if(setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(int)) < 0) {
    fprintf(stderr, "could not set SO_REUSEADDR");
    return 1;
  }
  if (bind(sockfd, (struct sockaddr *) &http_addr, sizeof(http_addr)) < 0) {
    fprintf(stderr, "could not bind to port %d\n", port);
    return 1;
  }
  if (listen(sockfd, MAXWAIT) < 0) {
    fprintf(stderr, "could not listen\n");
    return 1;
  }

  signal(SIGINT, term);
  signal(SIGPIPE, SIG_IGN);

  stack = malloc(THREADS * STACKSIZE);
  for (nt = 0; nt < THREADS; nt++) {
    if ((threads[nt].pid = clone(thr, stack += STACKSIZE,
        CLONE_FS | CLONE_FILES | CLONE_SIGHAND | CLONE_VM,
        threads + nt)) < 0) {
      fprintf(stderr, "thread creation failed\n");
      return 1;
    }
  }

  pause();
  return 0;
}