Thomas Huth, on Wed 10 Feb 2016 11:08:55 +0100, wrote: > On 10.02.2016 10:28, Samuel Thibault wrote: > > Thomas Huth, on Wed 10 Feb 2016 09:05:32 +0100, wrote: > >>> -#define SLIRP_MSIZE (IF_MTU + IF_MAXLINKHDR + offsetof(struct mbuf, > >>> m_dat) + 6) > >>> +#define SLIRP_MSIZE\ > >>> + (offsetof(struct mbuf, m_dat) + IF_MAXLINKHDR + TCPIPHDR_DELTA + > >>> IF_MTU) > >> > >> I'm somehow having a hard time to understand why TCPIPHDR_DELTA is used > >> here. As far as I understand, TCPIPHDR_DELTA is the difference between > >> the size of struct tcpiphdr and the size of the IPv4 + TCP header. But > >> if it's just the difference, where does the base size of the headers > >> come from in this define, since the headers are stored in the mbuf, too, > >> aren't they? ... I've got the feeling that I miss something here, could > >> you enlighten me? > > > > TCP/IP headers are within IF_MTU. > > Ah, of course, that makes sense, thanks! ... so in the old definition of > SLIRP_MSIZE, the TCP/IP headers were counted twice, I guess?
Something like this, yes. The formula was looking very magic (what is that 6 from?), so we rewrote it to make it clear for sure. Samuel
