Packet Length via ip_len failed?

[kf]

hi, i’m try fetch the tcp/ip length by ip_len. Can some say me whats wrong? I get a size more than 1452 bytes!!

DWORD dwDataLength = pIpHeader->ip_len - ( pIpHeader->ip_hl*4 + pTcpHeader->th_off*4);

PS: right, the size could be fetched by using: (that code give me a perfect length, but the code above do not!!)

DWORD dwDataLength = PacketBuffer.m_Length - (sizeof(ether_header) + pIpHeader->ip_hl*4 + pTcpHeader->th_off*4);

but i want try it on an other way…please help..

[kf]

i found the answer!.

unsigned short length = ntohs(pIpHeader->ip_len) - ( pIpHeader->ip_hl*4 + pTcpHeader->th_off*4);

can someone say yes or no? 😀

[Vadim Smirnov]

pIpHeader->ip_len is in network byte order, so it should be:

DWORD dwDataLength = ntohs(pIpHeader->ip_len) - ( pIpHeader->ip_hl*4 + pTcpHeader->th_off*4);

[Author]

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