tftp 服务器实现

[裴国兴]

#include "stdafx.h"
#include <winsock.h>
#include <signal.h>
#include <assert.h>

#define close closesocket

typedef int socklen_t;

int wait_ack(int fudp, u_short ackno, int *pcancel)
{
int result;
char buffer[1024];
fd_set readfds;
FD_ZERO(&readfds);
FD_SET(fudp, &readfds);
struct timeval timeout;
timeout.tv_sec = 2;
timeout.tv_usec = 0;
if (select(fudp+1, &readfds, 0, 0, &timeout)) {
u_short *ackhdr = (u_short*)buffer;
result = recv(fudp, buffer, sizeof(buffer), 0);
if (result < 4)
return 0;
if (ackhdr[0]==htons(4)
&& ackhdr[1]==htons(ackno))
return 1;
if (ackhdr[0]==htons(5))
pcancel[0] = 1;
}
return 0;
}

int stable_send(int fudp, const void *sndbuf, socklen_t len, u_short
ackno, int *pcancel)
{
const char *psndbuf = (const char*)sndbuf;
int result = send(fudp, psndbuf, len, 0);
for (int i=0; i<5 && result==len && *pcancel==0; i++) {
if (wait_ack(fudp, ackno, pcancel))
return 1;
result = send(fudp, psndbuf, len, 0);
}
if (result != len)
pcancel[0] = 1;
return 0;
}

int tftp_exec(const char *buffer, socklen_t len,
const struct sockaddr *paddr, socklen_t sinlen)
{
int result;
int count = 0;
u_short tftpidx, *tftphdr, *reqhdr;

char sndbuf[1024];
int fudp = socket(AF_INET, SOCK_DGRAM, 0);
assert (fudp != -1);
result = connect(fudp, paddr, sinlen);
if (result == -1)
return result;

char msg_deny[]="Access Deny";
char msg_badop[]="Invaliadate Operation";
char msg_notfound[]="TFTP File Not Found";

do {
reqhdr = (u_short*)buffer;
tftphdr = (u_short*)sndbuf;
if (len<9 || reqhdr[0]!=htons(1)) {
tftphdr[0] = htons(5);
if (len < 9)
break;
count = 4;
if (reqhdr[1] == htons(2)) {
tftphdr[1] = htons(2); count+=sizeof(msg_deny);
memcpy(tftphdr+2, msg_deny, sizeof(msg_deny));
} else {
tftphdr[1] = htons(4); count+=sizeof(msg_badop);
memcpy(tftphdr+2, msg_badop, sizeof(msg_badop));
}
send(fudp, sndbuf, count, 0);
} else {
FILE *fbin = fopen(buffer+2, "rb");
if (fbin == NULL) {
tftphdr[0] = htons(5);
tftphdr[1] = htons(2); count=sizeof(msg_notfound)+4;
memcpy(tftphdr+2, msg_notfound, sizeof(msg_notfound));
send(fudp, sndbuf, count, 0);
break;
}
printf("get file: %s\n", buffer+2);
tftpidx = 1;
tftphdr = (u_short*)sndbuf;
int cancel = 0;
do {
tftphdr[0] = htons(3);
tftphdr[1] = htons(tftpidx);
count = fread(sndbuf+4, 1, 512, fbin);
if (!stable_send(fudp, sndbuf, count+4, tftpidx,
&cancel)) {
printf("error ocurr!\n");
break;
}
tftpidx++;
}while(count>0 && cancel==0);
fclose(fbin);
}
} while (FALSE);
close(fudp);
return 0;
}

int tftpd_run(int argc, char *argv[])
{
int result;
struct sockaddr_in sinaddr;
struct sockaddr *paddr = NULL;
int fudp = socket(AF_INET, SOCK_DGRAM, 0);
paddr = (struct sockaddr*)&sinaddr;
sinaddr.sin_family = AF_INET;
sinaddr.sin_port = htons(69);
sinaddr.sin_addr.s_addr = htonl(INADDR_ANY);
result = bind(fudp, paddr, sizeof(sinaddr));

for (;;) {
int len, sinlen;
char buffer[1024];
sinlen = sizeof(sinaddr);
len = recvfrom(fudp, buffer, sizeof(buffer),
0, paddr, &sinlen);
if (len > 0)
tftp_exec(buffer, len, paddr, sinlen);
}

close(fudp);
return 0;
}

int main(int argc, char* argv[])
{
WSADATA data;
WSAStartup(0x101, &data);
tftpd_run(argc, argv);
WSACleanup();
return 0;
}

TFTP 修正
tftp 服务器实现