我用UDP的netbuf_ref函数构建的包发送不了呀？为什么？（问题已解决！）

发布于 2013-05-25 11:41:00 浏览：5965 订阅该版

系统自带的例子是可以的```void udpecho_entry(void *parameter)
{
	struct netconn *conn;
	struct netbuf *buf;
	struct ip_addr *addr;
	unsigned short port;

conn = netconn_new(NETCONN_UDP);
	netconn_bind(conn, IP_ADDR_ANY, 7);

while(1)
	{
        /* received data to buffer */
		buf = netconn_recv(conn);

addr = netbuf_fromaddr(buf);
		port = netbuf_fromport(buf);

/* send the data to buffer */
		netconn_connect(conn, addr, port);

/* reset address, and send to client */
		buf->addr = RT_NULL;
		netconn_send(conn, buf);

/* release buffer */
		netbuf_delete(buf);
	}
}```

但他是直接把收到的包发回去，我自己构建的包就是发不出去。
我试了这个例子：http://www.rt-thread.org/phpBB3/viewtopic.php?t=367
```int udp()
{
struct netconn *conn;
struct netbuf *buf;
struct ip_addr addr;
char *data;
char text[] = "A static text";
int i;
/* 创建一个新的连接*/
conn = netconn_new(NETCONN_UDP);
/* 设置远程主机的IP地址*/
addr.addr = htonl(0x0a000001);
/* 连接远程主机*/
netconn_connect(conn, &addr, 7000);
/* 创建一新的netbuf */
buf = netbuf_new();
data = netbuf_alloc(buf, 10);
/*创建一些立即数*/
for(i = 0; i < 10; i++)
data* = i;
/* 发送立即数*/
netconn_send(conn, buf);
netbuf_ref(buf, text, sizeof(text));
/* 发送text */
netconn_send(conn, buf);
/*分配connection 和 netbuf */
netconn_delete(conn);
netconn_delete(buf);
｝```
发现
```data = netbuf_alloc(buf, 10);
/*创建一些立即数*/
for(i = 0; i < 10; i++)
data* = i;```
所创建的数据可以发出去。
而```netbuf_ref(buf, text, sizeof(text));
/* 发送text */
netconn_send(conn, buf);```
创建的包就是发不出去。
查看了内存，发现他们的type有区别。
一个为0，一个为0x02。不知道咋办。
想要一个UDP构建封包并发送的标准的例子~

10 个回答

aishiqi 2013-05-25

这家伙很懒，什么也没写！

aishiqi 2013-05-25

这家伙很懒，什么也没写！

bernard 2013-05-25

这家伙很懒，什么也没写！

aishiqi 2013-05-25

这家伙很懒，什么也没写！

aishiqi 2013-05-25

这家伙很懒，什么也没写！

问题解决，WIFI驱动漏洞，找了我两天，都快吐了，还是给跟了出来。
位于wlan_tx.c的SendSinglePacket()下

```
int SendSinglePacket(WlanCard *cardinfo, struct pbuf *packet)
{
	WlanCard *card = cardinfo;
	int ret = WLAN_STATUS_SUCCESS;
	TxPD LocalTxPD;
	TxPD *pLocalTxPD = &LocalTxPD;
	u8 *ptr = card->TmpTxBuf;
	struct pbuf *phead;
	int curlen;

if (card->MediaConnectStatus == WlanMediaStateDisconnected)
	{
		WlanDebug(WlanMsg,"wlan did not connect
");
		return -1;
	}

rt_memset(pLocalTxPD, 0, sizeof(TxPD));
	pLocalTxPD->TxPacketLength = packet->tot_len;

/* offset of actual data */
	pLocalTxPD->TxPacketLocation = sizeof(TxPD);

if (pLocalTxPD->TxControl == 0)
	{
		/* TxCtrl set by user or default */
		pLocalTxPD->TxControl = card->PktTxCtrl;
	}

rt_memcpy(pLocalTxPD->TxDestAddrHigh, packet->payload, MRVDRV_ETH_ADDR_LEN);
	rt_memcpy(ptr, pLocalTxPD, sizeof(TxPD));

ptr += sizeof(TxPD);
	phead = (struct pbuf*) packet;
	curlen = 0;
	if (phead->tot_len >= 2048)
	{
		WlanDebug(WlanErr,"tx packet size is too long
");
		goto done;
	}
	while (phead != RT_NULL && curlen < phead ->tot_len)
	{
		rt_memcpy(ptr + curlen, phead->payload, phead->len);
		curlen += phead->len;
		phead = phead->next;
	}

ret = sbi_host_to_card(card, MVMS_DAT, card->TmpTxBuf,
			packet->tot_len + sizeof(TxPD));
	if (ret)
	{
		WlanDebug(WlanErr,"SendSinglePacket Error: sbi_host_to_card failed: 0x%X
",ret);
		goto done;
	}

WlanDebug(WlanEncy,"Data => FW
");

done:
	/* need to be freed in all cases */
	return ret;
}
```

请注意这儿：

```
	
	while (phead != RT_NULL && curlen < phead ->tot_len)
	{
		rt_memcpy(ptr + curlen, phead->payload, phead->len);
		curlen += phead->len;
		phead = phead->next;
	}
```

问题在于链表头的tot_len才是真正的tot_len，而程序在执行phead = phead->next;后phead指针改变了，导致tot_len不是真正的tot_len。实际跟踪中的表现现象是没有循环足够的次数把所有的链表数据连在一起。
改成这个样子就行了：

```
	totle_len= phead ->tot_len;	 //aishiqi added 2013-5-25
	while (phead != RT_NULL && curlen <totle_len )
	{
		rt_memcpy(ptr + curlen, phead->payload, phead->len);
		curlen += phead->len;
		phead = phead->next;
	}
```

改过后测试正常！问题解决~~