TM4C129XNCZAD: How Can I detect IP conflict on the network

thanks, Charles

these articles were really helpfull and I depend on these functions from TI stack

- the read arp packets using arp hook during NDK boot (only)
- concmping I modified this function alittle bit to refactor it and to fit in my app

first senario is when my node is statically configured with an IP already on the network

- the NDK boot task in nature sends an ARP Broadcasting message announcing itself on the network so if this node already exists (conflict)
the remote node rely with its mac address which is different than the current node mac so during boot task we set an ARP hook and read the received messages and if we received our configured IP as source sender with different MAC that is considered as a conflict and we take action for me I disable the stack, but you can disable the interface and check it periodically

for this approach I used there code snippets

LLI_setARPHook(fxnARPCallback); //to set the arp hook before starting (booting) the stack

do
{
    rc= NC_NetStart(hCfgIpAddr,\
    SoAd_vNetworkOpenHook,\
    SoAd_vNetworkCloseHook,\
    SoAd_vNetworkIPAddressChangeHook);
}while(rc> 0);

and for the hook itself 

void fxnARPCallback(void* data)
{
    ARPHDR* ARPPacketHDR;
    ARPPacketHDR = (ARPHDR*)( ((INT8U*)data) + 14U);

    if( memcmp((ARPPacketHDR->IPSrc),&(SoAd_objstrDCFGType.objstrIPSettings.u32LocalIP), (INT32U) 4U ) == 0U)
    {
        if( memcmp((ARPPacketHDR->SrcAddr), SoAd_objstrDCFGType.objstrIPSettings.u8MACAdressArray, (INT32U) 6U) != 0U)
        {
            /*conflict is detected */
        }
    }
}

then to detech conflcit upon changing the IP by removing and adding ip entries before doing such thing we need to ping this new IP if it is not pinging then the ip is not used and we can change our IP configuration if pings successfully then the ip is used and replying to me and log a message with conflcit detected too at runtime  

my version of ping function was like the following

INT8 SoAd_Ping( IPN *IPAddr, INT8S s8Attempts )
{
    fd_set              ibits;
    INT32S              cc,fromlen;
    UINT16              cnt_send=0, cnt_recv=0;     /* Packets send and received */
    SOCKET              s;                          /* ICMP socket file descriptor */
    struct  sockaddr_in to;                         /* who to ping */
    struct  sockaddr_in from;                       /* who replied */
    static INT8S        pBuf[30] = {0};
    struct  timeval     timeout;                    /* Timeout struct for select */
    INT32U              timestart;

    INT8S               retCode;
    INT8U               SucessAttempts;

    (void)fdOpenSession(TaskSelf());
    retCode = Ping_Success;
    SucessAttempts = 0U;
    /* Create the ICMP Socket */
    s = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
    if( s == INVALID_SOCKET )
    {
        SoAd_vmLogError1(&objstrSoAdModuleInfoType, "failed socket create (%d)",fdError());
        retCode = Ping_INVALID_SOCKET;
    }
    /* Create to "to" address */
    bzero( &to, sizeof(struct sockaddr_in));
    to.sin_family       = AF_INET;
    to.sin_addr.s_addr  = *IPAddr;
    /* Create to "from" address */
    bzero( &from, sizeof(struct sockaddr_in));
    from.sin_family     = AF_INET;
    /* Set socket option to allow us to broadcast */
    cc = 1;
    if( setsockopt( s, SOL_SOCKET, SO_BROADCAST, &cc, sizeof(INT32S) ) < 0 )
    {
        SoAd_vmLogError1(&objstrSoAdModuleInfoType, "failed set IP broadcast (%d)",fdError());
        retCode = Ping_Failed_SetIPBroadcast;
    }
    /* Configure our timeout to be 0.5 seconds */
    timeout.tv_sec  = 0;
    timeout.tv_usec = 500000;

    SoAd_vmLogActivity5(&objstrSoAdModuleInfoType, "Pinging %d.%d.%d.%d with %d data bytes",\
                        (INT32U)(*IPAddr & 0xFFU),\
                        (INT32U)((*IPAddr >> 8)&0xFFU),\
                        (INT32U)((*IPAddr >> 16)&0xFFU),\
                        (INT32U)((*IPAddr >> 24)&0xFFU),\
                        PING_DATALEN );
    /* Ping loop */
    while( cnt_send < s8Attempts )
    {
        /* Use send count for sequence - starts at "1" */
        cnt_send++;
        memset(pBuf, 0x00, sizeof(char)*40);
        /* Build the ping packet */
        SoAd_BuildPing( pBuf, cnt_send );
        /* Get the time now */
        timestart = llTimerGetTime(0);
        cnt_recv = 0;
        /* Send the ping */
        cc = sendto( s, pBuf, PING_DATALEN, 0,(struct sockaddr *)&to, sizeof(to) );
        if( cc < 0 )
        {
            SoAd_vmLogError1(&objstrSoAdModuleInfoType, "failed sento (%d)",fdError());
        }
        else if( cc != PING_DATALEN )
        {
            SoAd_vmLogError0(&objstrSoAdModuleInfoType, "sento - partial write!");
        }
        else{
            while( (timestart+2) > llTimerGetTime(0) )
            {
                /* Select for timeout period second */
                FD_ZERO(&ibits);
                FD_SET(s, &ibits);
                if( fdSelect( (INT32S)s, &ibits, 0, 0, &timeout ) < 0 )
                {
                    SoAd_vmLogError1(&objstrSoAdModuleInfoType, "failed select (%d)",fdError());
                    retCode = Ping_Failed_SelectSocket;
                    break;
                }
                /* Check for a reply */
                if( FD_ISSET(s, &ibits) )
                {
                    fromlen = sizeof(from);
                    cc = (INT32S)recvfrom( s, pBuf, PING_DATALEN, 0,(struct sockaddr *)&from, &fromlen );
                    if( cc < 0 )
                    {
                        SoAd_vmLogError1(&objstrSoAdModuleInfoType, "failed recvfrom (%d)",fdError());
                        retCode = Ping_Failed_recvfrom;
                        break;
                    }
                    /* Check the reply. Bump the recv count if good reply */
                    if( SoAd_CheckPing( pBuf, cnt_send, cc, IPAddr) )
                    {
                        SucessAttempts++;
                        cnt_recv++;
                        break;
                    }
                }
            }
            /* If send is more than reply, then we missed a reply */
            if( !cnt_recv )
            {
                SoAd_vmLogError0(&objstrSoAdModuleInfoType, "Reply timeout");
                retCode = Ping_Reply_Timeout;
            }
        }
    }

    if(retCode == Ping_Success && SucessAttempts > s8Attempts/2)
    {
        retCode = Ping_Success;
    }
    else
    {
        /*do nothing*/
        retCode = Ping_Fail;
    }

    if( s != INVALID_SOCKET )
        fdClose( s );

    return retCode;
}

static INT8 SoAd_CheckPing( INT8S *ps8Buf,INT16U u16Seq,INT32S s32NumberOfBytes, IPN* ps8IpStr)
{
    INT32S     ICMPLen;
    INT16U     Id,Seq;
    INT8U      retCode;

    retCode = Ping_SUCCESS_ECHOREPLY;
    /* Get header pointers */

    /* Get the total length of the ICMP message */
    ICMPLen = (uint)(HNC16( ((IPHDR *)ps8Buf)->TotalLen )) - ( (((IPHDR *)ps8Buf)->VerLen & 0xF) * 4 );

    /* Verify the ICMP type */
    if( ((ICMPHDR *)(ps8Buf+( (((IPHDR *)ps8Buf)->VerLen & 0xF) * 4 )))->Type != ICMP_ECHOREPLY )
        retCode = Ping_NOTICMP_ECHOREPLY ;

    /* Get the seq and the id */
    Seq = (INT32S)HNC16(((ICMPREQHDR *)((ICMPHDR *)(ps8Buf+( (((IPHDR *)ps8Buf)->VerLen & 0xF) * 4 )))->Data)->Seq);
    Id  = (INT32S)HNC16(((ICMPREQHDR *)((ICMPHDR *)(ps8Buf+( (((IPHDR *)ps8Buf)->VerLen & 0xF) * 4 )))->Data)->Id);

    /* If the reply is incorrect, don't continue */
    if( Id != PING_IDENTIFICATION || Seq != u16Seq )
    {
        SoAd_vmLogError4(&objstrSoAdModuleInfoType, "Non-matching echo reply from %d.%d.%d.%d", \
                         (INT32U)(*ps8IpStr & 0xFFU),\
                         (INT32U)((*ps8IpStr >> 8)&0xFFU),\
                         (INT32U)((*ps8IpStr >> 16)&0xFFU),\
                         (INT32U)((*ps8IpStr >> 24)&0xFFU));
        retCode = Ping_NonMatching_ECHOREPLY;
    }

    /* Print out data on correct reply */
    SoAd_vmLogActivity7(&objstrSoAdModuleInfoType, "Reply from %d.%d.%d.%d, with %d bytes, Seq=%u, TTL = %d", \
                        (INT32U)(*ps8IpStr & 0xFFU),\
                        (INT32U)((*ps8IpStr >> 8)&0xFFU),\
                        (INT32U)((*ps8IpStr >> 16)&0xFFU),\
                        (INT32U)((*ps8IpStr >> 24)&0xFFU),\
                        ICMPLen-8,\
                        Seq,\
                        ((IPHDR *)ps8Buf)->Ttl);

    /* Validate the data payload */
    if( ICMPLen != PING_DATALEN )
    {
        SoAd_vmLogError2(&objstrSoAdModuleInfoType, "Data length error in reply (%d of %d)", s32NumberOfBytes, PING_DATALEN);
        retCode = Ping_DataLenError_ECHOREPLY;
    }


    if( *(UINT8 *)((ps8Buf+( (((IPHDR *)ps8Buf)->VerLen & 0xF) * 4 )+8)) != (UINT8)('0'+8) )
    {
        SoAd_vmLogError3(&objstrSoAdModuleInfoType, "Data verification error in reply (%d 0x%x 0x%x)", \
                         s32NumberOfBytes, \
                         *(UINT8 *)((ps8Buf+( (((IPHDR *)ps8Buf)->VerLen & 0xF) * 4 )+s32NumberOfBytes)), \
                         '0'+s32NumberOfBytes );
        retCode = Ping_DataVerFailed_ECHOREPLY;
    }
    return retCode;
}

static void SoAd_BuildPing( INT8S *ps8Buf, INT16U u16seq )
{
    *(ps8Buf+8) = '0'+8;
    /* Get pointers to the ICMP and ICMPREQ headers */

    /* Fill out echo request */
    ((ICMPHDR *)ps8Buf)->Type   = ICMP_ECHO;
    ((ICMPHDR *)ps8Buf)->Code   = 0;
    ((ICMPREQHDR *)(((ICMPHDR *)ps8Buf)->Data))->Id    = HNC16(PING_IDENTIFICATION);
    ((ICMPREQHDR *)(((ICMPHDR *)ps8Buf)->Data))->Seq   = HNC16(u16seq);

    /* Checksum the ICMP header */
    /* Although the checksum function is reentrant, we follow the rules */
    /* and call llEnter()/llExit() since this is a stack function. */
    llEnter();
    ICMPChecksum( (ICMPHDR *)ps8Buf, PING_DATALEN );
    llExit();
}