On Fri, Oct 30, 2015 at 06:48:16PM +0100, Mike Belopuhov wrote:
> On Fri, Oct 30, 2015 at 18:27 +0100, Alexander Bluhm wrote:
> > On Fri, Oct 30, 2015 at 02:04:52PM +0100, Reyk Floeter wrote:
> > > > Socket splicing somove() does the same thing. I will change it to
> > > > use m_resethdr() after that got commited.
> >
> > I just compared code in somove() with m_resethdr(). Socket splicing
> > has to clear the whole packet header, not only the pf part. I think
> > this is also useful for pair(4) as it should behave like a cable.
> >
> > Resetting the other m_flags seems wrong. I have put the M_PKTHDR
> > into an assert. If it is not an packet header, the memset() could
> > overwrite mbuf data.
> >
> > ok?
> >
>
> Resetting flags that are set on input (e.g. M_CONF, M_AUTH, etc.) is
> not wrong since input on the other pair has not happened yet and it
> might provide more problems than shortcuts. I'm not certain which
> flags may still be of use before the other pair figures it on its
> own. Do you have any examples of such flags?
I think flags that must be preserverd are
- M_ZEROIZE
- M_EXT
In sys/mbuf.h Flags are split into mbuf flags and mbuf pkthdr flags.
As we clear the packet header but keep the data, we should probably
only clear the mbuf pkthdr flags.
Something like this flag combination?
bluhm
Index: kern/uipc_mbuf.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/kern/uipc_mbuf.c,v
retrieving revision 1.209
diff -u -p -r1.209 uipc_mbuf.c
--- kern/uipc_mbuf.c 30 Oct 2015 12:54:36 -0000 1.209
+++ kern/uipc_mbuf.c 30 Oct 2015 18:00:59 -0000
@@ -253,13 +253,18 @@ m_inithdr(struct mbuf *m)
void
m_resethdr(struct mbuf *m)
{
- /* like the previous, but keep any associated data and mbufs */
- m->m_flags = M_PKTHDR;
- memset(&m->m_pkthdr.pf, 0, sizeof(m->m_pkthdr.pf));
- m->m_pkthdr.pf.prio = IFQ_DEFPRIO;
+ int len = m->m_pkthdr.len;
+
+ KASSERT(m->m_flags & M_PKTHDR);
+ m->m_flags &= (M_EXT|M_PKTHDR|M_EOR|M_EXTWR|M_ZEROIZE);
- /* also delete all mbuf tags to reset the state */
+ /* delete all mbuf tags to reset the state */
m_tag_delete_chain(m);
+
+ /* like m_inithdr(), but keep any associated data and mbufs */
+ memset(&m->m_pkthdr, 0, sizeof(m->m_pkthdr));
+ m->m_pkthdr.pf.prio = IFQ_DEFPRIO;
+ m->m_pkthdr.len = len;
}
struct mbuf *
Index: kern/uipc_socket.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/kern/uipc_socket.c,v
retrieving revision 1.142
diff -u -p -r1.142 uipc_socket.c
--- kern/uipc_socket.c 24 Aug 2015 14:28:25 -0000 1.142
+++ kern/uipc_socket.c 30 Oct 2015 17:06:57 -0000
@@ -1325,10 +1325,8 @@ somove(struct socket *so, int wait)
goto release;
m->m_nextpkt = NULL;
if (m->m_flags & M_PKTHDR) {
- m_tag_delete_chain(m);
- memset(&m->m_pkthdr, 0, sizeof(m->m_pkthdr));
+ m_resethdr(m);
m->m_pkthdr.len = len;
- m->m_pkthdr.pf.prio = IFQ_DEFPRIO;
}
/* Send window update to source peer as receive buffer has changed. */
