Sorry, discard last mail... those 140 bytes are the __TCP PAYLOAD__ (check it with wireshark) so the datagram ip size is: IP HEADER + TCP HEADER + TCP PAYLOAD = 140+20+20=180...isn't it? On Mon, Sep 6, 2010 at 2:04 AM, Nicola Padovano <nicola.padovano@xxxxxxxxx> wrote: > those 140 bytes are the __tcp payload__ so the payload of IP is: Ip > header +TCP payload = 180... > isn't it? > > On Mon, Sep 6, 2010 at 1:47 AM, Changli Gao <xiaosuo@xxxxxxxxx> wrote: >> On Mon, Sep 6, 2010 at 7:19 AM, Nicola Padovano >> <nicola.padovano@xxxxxxxxx> wrote: >>> the default value for mtu (in hping) is 16 bytes!!! what does it mean? >>> maybe hping (against the rfc) use the fragmentation on the IP >>> __payload__ and not on the whole IP packet...what do you think? you >>> can check this with wireshark! >>> in fact i typed this hping line: >>> >>> hping -m 160 -d 140 -c 1 localhost >> >> Since you use hping, I think it has noting to do with the kernel. >> Hping fragments packets in user space other than kernel space. >> >>> >>> so we have a IP DATAGRAM size = 140data+20ipheader+20tcpheader > MTU=160 >>> >>> but there isn't fragmentation (check it with wireshark) but ip >>> datagram size is greater than mtu! >>> >>> So why there isn't fragmentation? because (i suppose) the >>> fragmentation work only on the IP payload: >>> IP paylaod = 140data + 20tcpheader = 160 = MTU => no fragmentation! >> >> Fragmentation is in IP layer. sizeof(ip packet) <= MTU. In your case, >> 140data + 20ipheader = 160 = MTU => no fragmentation. >> >>> >>> what do you think? i'm pretty sure of what i say.... >>> >> >> >> >> -- >> Regards, >> Changli Gao(xiaosuo@xxxxxxxxx) >> > > > > -- > Nicola Padovano > e-mail: nicola.padovano@xxxxxxxxx > web: http://npadovano.altervista.org > -- Nicola Padovano e-mail: nicola.padovano@xxxxxxxxx web: http://npadovano.altervista.org -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
