net.c

   1 #include <sys/types.h>
   2 #include <string.h>
   3 #include <stdio.h>
   4 #include <stdlib.h>
   5
   6 #ifndef WIN32
   7         #include <sys/socket.h>
   8 #else
   9         #include <winsock.h>
  10 #endif
  11
  12 #include "net.h"
  13 #include "crc32.h"
  14 #include "error.h"
  15
  16 /*
  17 PACKET:
  18         4 bytes    CRC32 (made only of data)
  19         4 bytes    sender
  20         4 bytes    recipient
  21         n bytes    data
  22 */
  23
  24
  25 /* packet = data to transmit
  26  * len = length of data
  27  * addr = recipient's address
  28  * sender = sender's (my) ID
  29  * recipient = recipient's ID
  30  */
  31 unsigned char *p;
  32 int alloc_len = 0;
  33 void send_packet(char *packet,int len,const struct sockaddr* addr,int sender,int recipient)
  34 {
  35         unsigned long crc=crc32((unsigned char *)packet,len);
  36         if (!p) p=mem_alloc(len+12);
  37         else if (len > alloc_len) {
  38             p=mem_realloc(p,len+12);
  39             alloc_len = len;
  40         }
  41         if (!p)return;  /* not enough memory */
  42         memcpy(p+12,packet,len);
  43         p[0]=(char)(crc & 0xff);crc>>=8;  /* CRC 32 */
  44         p[1]=(char)(crc & 0xff);crc>>=8;
  45         p[2]=(char)(crc & 0xff);crc>>=8;
  46         p[3]=(char)(crc & 0xff);
  47
  48         p[4]=(char)(sender & 0xff);sender>>=8;  /* sender */
  49         p[5]=(char)(sender & 0xff);sender>>=8;
  50         p[6]=(char)(sender & 0xff);sender>>=8;
  51         p[7]=(char)(sender & 0xff);
  52
  53         p[8]=(char)(recipient & 0xff);recipient>>=8;  /* recipient */
  54         p[9]=(char)(recipient & 0xff);recipient>>=8;
  55         p[10]=(char)(recipient & 0xff);recipient>>=8;
  56         p[11]=(char)(recipient & 0xff);
  57
  58         sendto(fd,p,len+12,0,addr,sizeof(*addr));
  59 }
  60
  61
  62 /* packet = buffer for received data
  63  * max_len = size of the buffer
  64  * addr = sender's address is filled in
  65  * addr_len = size of addr
  66  * sender_server = check
  67  * recipient = recipient's (my) ID
  68  * sender = if !NULL sender's ID
  69  */
  70
  71 /* returns:     -1 on error
  72                 length of received data (data! not CRC nor sender's/recipient's ID
  73  */
  74 int recv_packet(char *packet,int max_len,struct sockaddr* addr,int *addr_len,int sender_server,int recipient,int *sender)
  75 /* sender_server:
  76                 1=check if sender is 0  (server)
  77                 0=don't check sender's ID
  78    recipient:   recipient's id
  79 server has: sender_server 0, recipient 0
  80 client has: sender_server 1, recipient my_id
  81 */
  82 {
  83         int retval;
  84         unsigned int crc;
  85         int s,r;
  86
  87         if (!p) p=mem_alloc(max_len+12);
  88         else if (max_len > alloc_len) {
  89             p=mem_realloc(p,max_len+12);
  90             alloc_len = max_len;
  91         }
  92         if (!p)return -1;  /* not enough memory */
  93         retval=recvfrom(fd,p,max_len+12,0,addr,(unsigned int *)addr_len);
  94         if (retval<12) {
  95                 mem_free(p);
  96                 return -1;
  97         }
  98         memcpy(packet,p+12,max_len);
  99         crc=p[0]+(p[1]<<8)+(p[2]<<16)+(p[3]<<24);
 100         s=p[4]+(p[5]<<8)+(p[6]<<16)+(p[7]<<24);
 101         if (sender)*sender=s;
 102         r=p[8]+(p[9]<<8)+(p[10]<<16)+(p[11]<<24);
 103         if (retval==-1)return -1;
 104         if (crc!=crc32((unsigned char *)packet,retval-12))return -1;
 105         if (r!=recipient)return -1;
 106         if (sender_server&&s)return -1;
 107         return retval-12;
 108 }
 109
 110 /* free packet buffer, called only when terminating */
 111 void free_packet_buffer() {
 112         if (p)
 113             mem_free(p);
 114         return;
 115 }