求助，一个UDP数据转发问题！
本帖最后由 zhanglong71 于 2013-10-04 15:55 编辑一个转发网络数据包的程序，想不通问题出在哪里！请高人指点。
实现的原理如下：
１.使用UDP协议。
登录过程如下：
２.客户端(Client)向转发服务器(Server)发送登录数据包。登录数据包中包括客户自己的ID号。
３.转发服务器(Server)将收到的登录数据包中的客户ID号及源ip+port记录下来。
客户端1向客户端2发送数据的过程如下：
４.客户端1向转发服务器发数据包,包内有源客户端ID1及目的客户端ID2。
５.转发服务器(Server)将从客户端收到的数据包中提取目的客户端ID2，以目的客户端ID2查找客户端登录时的ip+port。再将数据包发往此ip+port对应的客户端2。
执行一次数据传输后服务器端的数据如下：
receiving ...
received !
Client Node created ok!
send login ACK ok
Client login
receiving ...
received !
Client Node created ok!
send login ACK ok
Client login
receiving ...
received !
received data !
ready to forward data !
forward data from to !
receiving ...
received !
received data !
ready to forward data !
forward data from to !
receiving ...
其中：start.c-333表示客户端登录时的ID号及ip:port。
start.c-258表示数据从客户端1发往客户端2时的ID号:ip:port
问题：
１.比较与的信息后发现，登录时的ip地址与需要转发数据时找到的ip地址不同：
登录时的节点信息是“22345678901: 192.168.1.112: 9655”。而转发需要数据时，找到的节点信息却是“22345678901-192.168.1.103:9655”，两者的ip地址不同
似乎处错打印了源端的ip地址信息。但找不到哪里有问题。
２.这种数据转发及从recvfrom()中取得数据包的源ip+port的方式是否可行？
附代码如下：#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#if 1
#include "ptype.h"
#include "rbtree.h"
//#include "read.h"
#include "parse.h"
#endif
/*
*receive data as recv port
*/
int insertImsi(struct rb_root *root, struct clientNode_s *__clientNode, charsCmp_t cmp)
{
struct rb_node **new = &(root->rb_node), *parent = NULL;
/* Figure out where to put new node */
while (*new)
{
//struct mytype *this = container_of(*new, struct mytype, node);
struct clientNode_s *clientNode = container_of(*new, struct clientNode_s, node);
int result = cmp(__clientNode->clientImsi, clientNode->clientImsi);
parent = *new;
if (result < 0)
new = &((*new)->rb_left);
else if (result > 0)
new = &((*new)->rb_right);
else
return 0;
}
/* Add new node and rebalance tree. */
rb_link_node(&(__clientNode->node), parent, new);
rb_insert_color(&(__clientNode->node), root);
return 1;
}
int insertClientId(struct rb_root *root, struct clientNode_s *__clientNode, cmp_t cmp)
{
struct rb_node **new = &(root->rb_node), *parent = NULL;
/* Figure out where to put new node */
while (*new)
{
//struct mytype *this = container_of(*new, struct mytype, node);
struct clientNode_s *clientNode = container_of(*new, struct clientNode_s, node);
int result = cmp(__clientNode->clientId, clientNode->clientId);
parent = *new;
if (result < 0)
new = &((*new)->rb_left);
else if (result > 0)
new = &((*new)->rb_right);
else
return 0;
}
/* Add new node and rebalance tree. */
rb_link_node(&(__clientNode->node), parent, new);
rb_insert_color(&(__clientNode->node), root);
return 1;
}
struct clientNode_s *searchClientId(struct rb_root *root, unsignedint __clientId, cmp_t cmp)
{
struct rb_node *node = root->rb_node;
while (node)
{
struct clientNode_s *clientNode = container_of(node, struct clientNode_s, node);
int result = cmp(__clientId, clientNode->clientId);
if (result < 0)
node = node->rb_left;
else if (result > 0)
node = node->rb_right;
else
return clientNode;
}
return NULL;
}
struct clientNode_s *searchImsi(struct rb_root *root, char* __imsi, charsCmp_t cmp)
{
struct rb_node *node = root->rb_node;
while (node)
{
struct clientNode_s *clientNode = container_of(node, struct clientNode_s, node);
int result = cmp(__imsi, clientNode->clientImsi);
if (result < 0)
node = node->rb_left;
else if (result > 0)
node = node->rb_right;
else
return clientNode;
}
return NULL;
}
unsigned int uicmp(const unsigned int __arg1, const unsigned int __arg2)
{
return (__arg1 - __arg2);
}
#if 1
#if 1
int charsCmp(const char* __arg1, const char* __arg2)
{
int i;
for(i = 0; ((i < __arg1) && (i < CIMSI_LEN)); i++) /** Note: arg1 is the length of string **/
{
if(__arg1 != __arg2)
{
return__arg1 - __arg2;
}
}
return 0;
}
#else
unsigned int charsCmp(const char* __arg1, const char* __arg2, int __len)
{
for(int i = 0; (i < CIMSI_LEN) && (i < __len); i++)
{
if(__arg1 != __arg2)
{
return__arg1 - __arg2;
}
}
return 0;
}
#endif
#else
unsigned int charsCmp(const char* __arg1, const char* __arg2)
{
int i;
if(__arg1 != __arg2) /** 先比较长度 **/
{
return__arg1 - __arg2;
}
for(i = 1; (i < CIMSI_LEN) && (i < __arg1); i++)
{
if(__arg1 != __arg2)
{
return__arg1 - __arg2;
}
}
return 0;
}
#endif
int main(int argc, char *argv[])
{
//int i;
int sock_fd;
//int iLen = 0;
struct sockaddr_in myaddr;
struct sockaddr_in src_addr;
struct sockaddr_in dst_addr;
struct clientNode_s *dstNode;
struct clientNode_s *srcNode;
char dstImsi;
char srcImsi;
char format;
//unsigned int dstClientId = 0;
//unsigned int srcClientId = 0;
struct rb_root root = RB_ROOT;
char buf;
char value;
int iStrLen = 0;
int recv_num;
int recvlen;
if(2 > argc)
{
printf("argc\n");
exit(1);
}
if(-1 == (sock_fd = socket(PF_INET, SOCK_DGRAM, 0)))
{
printf("socket\n");
exit(2);
}
myaddr.sin_family = AF_INET;
myaddr.sin_port = htons(atoi(argv));
myaddr.sin_addr.s_addr = htonl(INADDR_ANY);
if(-1 == bind(sock_fd, (struct sockaddr *)&myaddr, sizeof(struct sockaddr_in)))
{
perror("bind");
exit(1);
}
while(1)
{
fprintf(stderr, "[%s-%d]receiving ... \n", __FILE__, __LINE__);
recvlen = sizeof(struct sockaddr_in);
bzero(buf, BUF_LEN);
recv_num = recvfrom(sock_fd, (char *)buf, sizeof(buf), 0,
(struct sockaddr *)&src_addr, (socklen_t *)&recvlen);
fprintf(stderr, "[%s-%d]received ! \n", __FILE__, __LINE__);
if(recv_num != -1)
{
iStrLen = strlen(buf);
iStrLen = iStrLen > recv_num? iStrLen:recv_num;
memcpy(value, buf, iStrLen);
parsePacketFormatId(value, format);
memcpy(value, buf, iStrLen);
parseSrcImsi(value, srcImsi);
memcpy(value, buf, iStrLen);
parseDstImsi(value, dstImsi);
if((strcmp(format, "data-send") == 0) || (strcmp(format, "data-ACK") == 0))
{
fprintf(stderr, "[%s-%d]received data !\n", __FILE__, __LINE__);
//dstNode = searchImsi(&root, srcImsi, strcmp);
dstNode = searchImsi(&root, dstImsi, strcmp);
if(NULL != dstNode)
{
/** received data and find the destination node, forward data **/
fprintf(stderr, "[%s-%d]ready to forward data !\n", __FILE__, __LINE__);
dst_addr.sin_family = AF_INET;
dst_addr.sin_port = dstNode->port;
dst_addr.sin_addr.s_addr = inet_addr(dstNode->loginAddr);
//memcpy(&dst_addr, dstNode->ipAddr, sizeof(dst_addr));
//int ret = sendto(sock_fd, buf, BUF_LEN, 0, (struct sockaddr *)dstNode->ipAddr, sizeof(struct sockaddr_in));
int ret = sendto(sock_fd, buf, BUF_LEN, 0, (struct sockaddr *)&dst_addr, sizeof(struct sockaddr_in));
if(-1 == ret)
{
fprintf(stderr, "[%s-%d]send data error !\n", __FILE__, __LINE__);
exit(2);
}
#if 1
fprintf(stderr, "[%s-%d]forward data from [%s-%s:%u] to [%s-%s:%u]!\n",
__FILE__, __LINE__,
srcImsi,
inet_ntoa(src_addr.sin_addr),
src_addr.sin_port,
dstImsi,
inet_ntoa(dst_addr.sin_addr),
dst_addr.sin_port);
#endif
}
else
{
fprintf(stderr, "[%s-%d]destination[%s] is not on line!\n", __FILE__, __LINE__, dstImsi);
}
}
else if(strcmp(format, "login-request") == 0) /** 登录请求，记录信息 **/
{
/** received login message **/
srcNode = searchImsi(&root, srcImsi, strcmp);
if(NULL == srcNode)
{
/** create new node **/
srcNode = malloc(sizeof(struct clientNode_s));
if(NULL != srcNode)
{
bzero(srcNode, sizeof(struct clientNode_s));
memcpy(srcNode->clientImsi, srcImsi, CIMSI_LEN);
memcpy(srcNode->ipAddr, &src_addr, sizeof(src_addr));
srcNode->clientStatus = STATUS_LGINSUC;/** 进入登录状态 **/
insertImsi(&root, srcNode, strcmp);
fprintf(stderr, "[%s-%d]Client Node[%s-%s:%u] created ok!\n",
__FILE__, __LINE__,
srcImsi,
inet_ntoa(src_addr.sin_addr),
src_addr.sin_port);
}
else
{
fprintf(stderr, "[%s-%d]malloc error. Client Node[%s] created failed!\n", __FILE__, __LINE__, srcImsi);
}
}
else
{
srcNode->clientStatus = STATUS_LGINSUC;/** 进入登录状态 **/
memcpy(srcNode->clientImsi, srcImsi, CIMSI_LEN);
memcpy(srcNode->ipAddr, &src_addr, sizeof(src_addr));
fprintf(stderr, "[%s-%d]Client[%s-%s:%u] login again !\n",
__FILE__, __LINE__,
srcImsi,
inet_ntoa(src_addr.sin_addr),
src_addr.sin_port);
}
setPacketFormat(buf, "login-ok");
int ret = sendto(sock_fd, buf, strlen(buf) + 1, 0, (struct sockaddr *)&src_addr, sizeof(struct sockaddr_in));
if(-1 == ret)
{
perror("sendto");
fprintf(stderr, "[%s-%d]sendto error !!!!!!\n", __FILE__, __LINE__ );
//exit(2);
}
else
{
fprintf(stderr, "[%s-%d]send login ACK ok\n", __FILE__, __LINE__ );
}
/**
* store the client
**/
strcpy(srcNode->loginAddr, inet_ntoa(src_addr.sin_addr));
srcNode->port = src_addr.sin_port;
fprintf(stderr, "[%s-%d]Client [%s: %s: %d] login \n",
__FILE__, __LINE__,
srcImsi,
inet_ntoa(((struct sockaddr_in *)(srcNode->ipAddr))->sin_addr),
((struct sockaddr_in *)(srcNode->ipAddr))->sin_port);
}
else if(strcmp(format, "login-out") == 0)
{
fprintf(stderr, "[%s-%d]Client[%s] logout!\n", __FILE__, __LINE__, srcImsi);
}
else
{
fprintf(stderr, "[%s-%d]buf[%s] is unrecognized!!!\n", __FILE__, __LINE__, buf);
}
}
}
close(sock_fd);
return0;
} 本帖最后由 zhanglong71 于 2013-10-04 22:12 编辑
在代码第257-264行之间加入打印节点信息的语句，两者显示的数据居然不一样！
显示结果如下：
ready to forward data !
forward data from to !
代码如下：
printNode(dstNode);
fprintf(stderr, "[%s-%d]forward data from [%s-%s:%u] to [%s-%s:%u]!\n",
__FILE__, __LINE__,
srcImsi,
inet_ntoa(src_addr.sin_addr),
src_addr.sin_port,
dstImsi,
inet_ntoa(((struct sockaddr_in *)(dstNode->ipAddr))->sin_addr),
((struct sockaddr_in *)(dstNode->ipAddr))->sin_port);
printNode(dstNode); 中间一次打印的dstNode的内容居然与前后两次的内容不一样！
其中的printNode如下：void printNode(struct clientNode_s *clientNode)
{
if(clientNode != NULL)
{
printf("[%s-%s:%u]\n",
clientNode->clientImsi,
inet_ntoa(((struct sockaddr_in *)(clientNode->ipAddr))->sin_addr),
((struct sockaddr_in *)(clientNode->ipAddr))->sin_port);
}
else
{
printf("null\n");
}
}
---------------------------------------------------------------------------------
打印信息不同的问题已解决。很可能是这样的原因：不能在printf打印语句中两次调用inet_ntoa()。
原因是inet_ntoa()会将执行的结果保存在一个静态存贮区，并返回此存贮区的地址。两次调用inet_ntoa()后，inet_ntoa()可能返回的都是同一个地址，但其中的内容只是最后一次处理后的内容。
另一个问题作备忘：手机上的客户端收不到转发的数据。用wireshark抓包发现，转发往手机的数据包长度已经超过1500Bytes。实际的包内有用信息大小不超过200。通过计算包内字符串长度，并只发送该长度的数据，手机上可以正常显示收到的数据。具体修改L250的BUF_LEN改成strlen(buf) + 1。
LZ good boy
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