[Bug 1849] udhcpc oversized packets bug

bugzilla at busybox.net bugzilla at busybox.net
Sun May 30 04:19:41 UTC 2010


https://bugs.busybox.net/show_bug.cgi?id=1849

--- Comment #3 from Denys Vlasenko <vda.linux at googlemail.com>  ---
RFC 791 says that all IP networks must support packets at least 576 octets big.
the question is, *what is included* in those 576 octets? Here is the text from
the RFC:

    Total Length is the length of the datagram, measured in octets,
    including internet header and data.  This field allows the length of
    a datagram to be up to 65,535 octets.  Such long datagrams are
    impractical for most hosts and networks.  All hosts must be prepared
    to accept datagrams of up to 576 octets (whether they arrive whole
    or in fragments).  It is recommended that hosts only send datagrams
    larger than 576 octets if they have assurance that the destination
    is prepared to accept the larger datagrams.

"Including internet header and data" means that in this case, "length" includes
IP headers and IP data (in case of DHCP packets, IP data will contain UDP
headers and then DHCP packet), bot does NOT include ethernet header, nor
ethernet CRC.

With ethernet header of 14 bytes, 576 + 14 = 590.

Here, for example, we also see *590* bytes mentioned:

http://technet.microsoft.com/en-us/library/cc749902.aspx

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