Re: RE : [lwip-users] Receiving RSTs

[Frédéric BERNON]

I did this test with last CVS HEAD (with a Vista workstation):

 

static void

tcp_connect_thread(void *arg)

{

int sock;

struct sockaddr_in local;

struct sockaddr_in to;

int iResult;

u32_t server_address;

 

/* initialize server address */

server_address = inet_addr("192.168.0.1");/*my pc*/

/* if we got a valid server address... */

if (server_address!=0) {

/* create new socket */

sock = socket( AF_INET, SOCK_STREAM, 0);

if (sock>=0) {

/* prepare local address */

memset(&local, 0, sizeof(local));

local.sin_family = AF_INET;

local.sin_port = htons(INADDR_ANY);

local.sin_addr.s_addr = htonl(INADDR_ANY);

/* bind to local address */

if (bind( sock, (struct sockaddr *)&local, sizeof(local))==0) {

/* prepare server address */

memset(&to, 0, sizeof(to));

to.sin_family = AF_INET;

to.sin_port = htons(62345);/* a port which is not opened*/

to.sin_addr.s_addr = server_address;

 

/* connect to server */

if ((iResult=connect( sock, (struct sockaddr *)&to, sizeof(to)))>=0) {

printf("connected success==%i [%i]\n", iResult, errno);

} else {

printf("connected error==%i [%i]\n", iResult, errno);

}

/* sleep */

sys_msleep(60000);/*let the time to see if any other packet is received*/

printf("close now\n");

 

}

/* close the socket */

closesocket(sock);

}

}

}

 

I got :

 

Starting lwIP, loopback interface IP is 127.0.0.1
Starting lwIP, local interface IP is 192.168.0.2
 0: \Device\NPF_{A6293F5E-B3DF-4E8D-8D01-C65870EEDD1E}
 1: \Device\NPF_{2DA42D7E-7436-40CD-901E-5D73107798B0}
MAC: 00:18:F3:E3:8D:8D
err_tcp==-4
connected error==-1 [0]
close now

-4 = ERR_ABRT

 

What I can said is the PC never send any RST packet (checked with wireshark). Of course, perhaps it's different with another pc OS.

 

But in all cases, in err_tcp, we set to NULL conn->pcb.tcp. So, we can't reuse the pcb. The only solution seems to close the socket and reopen it. If on RST, we receive any error, perhaps we could add a line like:

static void

err_tcp(void *arg, err_t err)

{

struct netconn *conn;

conn = arg;

LWIP_ASSERT("conn != NULL", (conn != NULL));

if (conn->pcb.tcp == NULL) return; /*<<<<<<<<<<<<<<<<<<<<<<<<<<*/

conn->pcb.tcp = NULL;

conn->err = err;

 

----- Original Message -----

From: "Jonathan Larmour" <address@hidden>

To: "Mailing list for lwIP users" <address@hidden>

Sent: Tuesday, December 11, 2007 11:45 PM

Subject: Re: RE : [lwip-users] Receiving RSTs

> address@hidden wrote:
>> 
Jonathan Larmour wrote:
>> 
>>> I wonder from what Aparna 
says:
>>>
>>>  
>>>
>>>>>         
When the Windows server is not up, the PC responds with a 
RST
>>>>>         for 
a received SYN. The connect() API returns an error, and 
the
>>>>>         
client retries connect() after every few 
seconds.
>>>>>       
>>>
>>>
>>> whether he/she is not closing 
the socket before calling connect again?
>>>
>>> Maybe 
the netconn API needs to explicitly disallow connects if 
>>> 
conn->err is
>>> set?
>>>
>>> Either way, 
if the socket isn't being closed, Aparna needs to fix 
>>> his/her 
code.
>>>   
>> 
>> Normally, the socket 
API allows calling connect for a second time (when 
>> the first call 
fails and the socket is not already connected).
> 
> Oh yes, of 
course you are right. Aparna's code should be valid for a BSD 
> sockets 
API, sorry.
> 
>> LwIP 
>> might not allow this, in 
which case we can argue if there is 
>> documentation missing or an 
assert (or a code change)...
> 
> I think in the short term, 
disallowing based on non-zero conn->err would 
> be best. This could be 
solved, but probably only when we have the richer 
> set of 
synchronisation primitives we've been thinking about elsewhere.
> 
> 
Jifl
> -- 
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