| Message ID | 20110927112038.42b5b3f8@BR8GGW75.de.ibm.com |
|---|---|
| State | New |
| Headers | show |
On 2011-09-27 11:20, Thomas Huth wrote: > > The two new variables "arp_requested" and "expiration_date" in the mbuf > structure have been added after the variable-sized "m_dat_" array. The > variables have to be added before the m_dat_ array instead. > Without this patch, the expiration_date gets clobbered by code that > accesses the m_dat_ array. > I experienced this problem with the code in slirp/tftp.c: The > tftp_send_data() function created a new packet with the m_get() > function (which fills-in a default expiration_date value). Then the > TFTP code cleared the data section of the packet, which accidentially > also cleared the expiration_date. This zeroed expiration_date then > finally causes the packet to be discarded during if_start(), so that > TFTP packets were not transmitted anymore. > > Signed-off-by: Thomas Huth <thuth@linux.vnet.ibm.com> > ------- > slirp/mbuf.h | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/slirp/mbuf.h b/slirp/mbuf.h > index 55170e5..37b9dbb 100644 > --- a/slirp/mbuf.h > +++ b/slirp/mbuf.h > @@ -82,12 +82,12 @@ struct m_hdr { > struct mbuf { > struct m_hdr m_hdr; > Slirp *slirp; > + bool arp_requested; > + uint64_t expiration_date; > union M_dat { > char m_dat_[1]; /* ANSI don't like 0 sized arrays */ > char *m_ext_; > } M_dat; > - bool arp_requested; > - uint64_t expiration_date; > }; > > #define m_next m_hdr.mh_next Thanks, applied. What generates "-------" as separator? Confuses git am here. You may want to use standard "---" in the future. Jan
On 27/09/2011 11:20, Thomas Huth wrote: > > The two new variables "arp_requested" and "expiration_date" in the mbuf > structure have been added after the variable-sized "m_dat_" array. The > variables have to be added before the m_dat_ array instead. > Without this patch, the expiration_date gets clobbered by code that > accesses the m_dat_ array. > I experienced this problem with the code in slirp/tftp.c: The > tftp_send_data() function created a new packet with the m_get() > function (which fills-in a default expiration_date value). Then the > TFTP code cleared the data section of the packet, which accidentially > also cleared the expiration_date. This zeroed expiration_date then > finally causes the packet to be discarded during if_start(), so that > TFTP packets were not transmitted anymore. > Thanks for the patch Thomas. I think we can add a comment to avoid this kind of mistake in the future. /* This is a "flexible array member". It should always remain * the last member of the structure. */ > Signed-off-by: Thomas Huth <thuth@linux.vnet.ibm.com> > ------- > slirp/mbuf.h | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/slirp/mbuf.h b/slirp/mbuf.h > index 55170e5..37b9dbb 100644 > --- a/slirp/mbuf.h > +++ b/slirp/mbuf.h > @@ -82,12 +82,12 @@ struct m_hdr { > struct mbuf { > struct m_hdr m_hdr; > Slirp *slirp; > + bool arp_requested; > + uint64_t expiration_date; > union M_dat { > char m_dat_[1]; /* ANSI don't like 0 sized arrays */ > char *m_ext_; > } M_dat; > - bool arp_requested; > - uint64_t expiration_date; > }; > > #define m_next m_hdr.mh_next >
On 2011-09-27 12:56, Fabien Chouteau wrote: > On 27/09/2011 11:20, Thomas Huth wrote: >> >> The two new variables "arp_requested" and "expiration_date" in the mbuf >> structure have been added after the variable-sized "m_dat_" array. The >> variables have to be added before the m_dat_ array instead. >> Without this patch, the expiration_date gets clobbered by code that >> accesses the m_dat_ array. >> I experienced this problem with the code in slirp/tftp.c: The >> tftp_send_data() function created a new packet with the m_get() >> function (which fills-in a default expiration_date value). Then the >> TFTP code cleared the data section of the packet, which accidentially >> also cleared the expiration_date. This zeroed expiration_date then >> finally causes the packet to be discarded during if_start(), so that >> TFTP packets were not transmitted anymore. >> > > Thanks for the patch Thomas. > > I think we can add a comment to avoid this kind of mistake in the > future. > > /* This is a "flexible array member". It should always remain > * the last member of the structure. > */ Good point, folded something like that in. Thanks, Jan
diff --git a/slirp/mbuf.h b/slirp/mbuf.h index 55170e5..37b9dbb 100644 --- a/slirp/mbuf.h +++ b/slirp/mbuf.h @@ -82,12 +82,12 @@ struct m_hdr { struct mbuf { struct m_hdr m_hdr; Slirp *slirp; + bool arp_requested; + uint64_t expiration_date; union M_dat { char m_dat_[1]; /* ANSI don't like 0 sized arrays */ char *m_ext_; } M_dat; - bool arp_requested; - uint64_t expiration_date; }; #define m_next m_hdr.mh_next
The two new variables "arp_requested" and "expiration_date" in the mbuf structure have been added after the variable-sized "m_dat_" array. The variables have to be added before the m_dat_ array instead. Without this patch, the expiration_date gets clobbered by code that accesses the m_dat_ array. I experienced this problem with the code in slirp/tftp.c: The tftp_send_data() function created a new packet with the m_get() function (which fills-in a default expiration_date value). Then the TFTP code cleared the data section of the packet, which accidentially also cleared the expiration_date. This zeroed expiration_date then finally causes the packet to be discarded during if_start(), so that TFTP packets were not transmitted anymore. Signed-off-by: Thomas Huth <thuth@linux.vnet.ibm.com> ------- slirp/mbuf.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)