On Wed, 9 Oct 2019 17:06:24 +0200 Morten Brørup <m...@smartsharesystems.com> wrote:
> > -----Original Message----- > > From: Stephen Hemminger [mailto:step...@networkplumber.org] > > Sent: Wednesday, October 9, 2019 5:02 PM > > > > On Wed, 9 Oct 2019 11:11:46 +0000 > > "Ananyev, Konstantin" <konstantin.anan...@intel.com> wrote: > > > > > Hi Morten, > > > > > > > > > > > Hi Konstantin and Stephen, > > > > > > > > I just noticed the same bug in your bpf and pcap libraries: > > > > > > > > You are using rte_pktmbuf_mtod(), but should be using > > rte_pktmbuf_read(). Otherwise you cannot read data across multiple > > segments. > > > > > > In plain data buffer mode expected input for BPF program is start of > > first segment packet data. > > > Other segments are simply not available to BPF program in that mode. > > > AFAIK, cBPF uses the same model. > > > > > > > > > > > > > > > Med venlig hilsen / kind regards > > > > - Morten Brørup > > > > > > > For packet capture, the BPF program is only allowed to look at first > > segment. > > pktmbuf_read is expensive and can cause a copy. > > It is only expensive if going beyond the first segment: > > static inline const void *rte_pktmbuf_read(const struct rte_mbuf *m, > uint32_t off, uint32_t len, void *buf) > { > if (likely(off + len <= rte_pktmbuf_data_len(m))) > return rte_pktmbuf_mtod_offset(m, char *, off); > else > return __rte_pktmbuf_read(m, off, len, buf); > } But it would mean potentially big buffer on the stack (in case)
