> From: dev [mailto:dev-boun...@dpdk.org] On Behalf Of Olivier Matz > Sent: Friday, July 10, 2020 3:41 PM > > On Fri, Jul 10, 2020 at 03:29:36PM +0200, Morten Brørup wrote: > > > From: Olivier Matz [mailto:olivier.m...@6wind.com] > > > Sent: Friday, July 10, 2020 3:16 PM > > > > > > On Fri, Jul 10, 2020 at 03:10:34PM +0200, Morten Brørup wrote: > > > > > From: Olivier Matz [mailto:olivier.m...@6wind.com] > > > > > Sent: Friday, July 10, 2020 2:41 PM > > > > > > > > > > On Fri, Jul 10, 2020 at 02:55:51PM +0800, Hongzhi Guo wrote: > > > > > > Per RFC768: > > > > > > If the computed checksum is zero, it is transmitted as all > ones. > > > > > > An all zero transmitted checksum value means that the > transmitter > > > > > > generated no checksum. > > > > > > > > > > > > RFC793 for TCP has no such special treatment for the checksum > of > > > > > zero. > > > > > > > > > > > > Fixes: 6006818cfb26 ("net: new checksum functions") > > > > > > Cc: sta...@dpdk.org > > > > > > > > > > > > Signed-off-by: Hongzhi Guo <guohongz...@huawei.com> > > > > > > --- > > > > > > v2: > > > > > > * Fixed commit tile > > > > > > * Fixed the API comment > > > > > > --- > > > > > > --- > > > > > > lib/librte_net/rte_ip.h | 18 +++++++++++++++--- > > > > > > 1 file changed, 15 insertions(+), 3 deletions(-) > > > > > > > > > > > > diff --git a/lib/librte_net/rte_ip.h > b/lib/librte_net/rte_ip.h > > > > > > index 292f63fd7..d03c77120 100644 > > > > > > --- a/lib/librte_net/rte_ip.h > > > > > > +++ b/lib/librte_net/rte_ip.h > > > > > > @@ -325,7 +325,7 @@ rte_ipv4_phdr_cksum(const struct > rte_ipv4_hdr > > > > > *ipv4_hdr, uint64_t ol_flags) > > > > > > * The pointer to the beginning of the L4 header. > > > > > > * @return > > > > > > * The complemented checksum to set in the IP packet > > > > > > - * or 0 on error > > > > > > + * or 0 if the IP length is invalid in the header. > > > > > > */ > > > > > > static inline uint16_t > > > > > > rte_ipv4_udptcp_cksum(const struct rte_ipv4_hdr *ipv4_hdr, > const > > > > > void *l4_hdr) > > > > > > > > 0 is a valid return value, so I suggest omitting it from the > return > > > value description: > > > > > > > > * @return > > > > - * The complemented checksum to set in the IP packet > > > > - * or 0 on error > > > > + * The complemented checksum to set in the IP packet. > > > > > > > > The comparison "if (l3_len < sizeof(struct rte_ipv4_hdr))" is > only > > > there to protect against invalid input; it prevents l4_len from > > > becoming negative. > > > > > > I don't get why "0 if the IP length is invalid in the header" > should > > > be removed from the comment: 0 is both a valid return value and > > > the value returned on invalid packet. > > > > To avoid confusion. We do not want people to add error handling for a > return value of 0. > > > > 0 is not a special value or an error, so it does not deserve explicit > mentioning. > > > > If we want to mention the return value for garbage input, we should > not use the wording "or 0", because this suggests that 0 is not a > normal return value. > > Ok, got it. > > So maybe this? > > The complemented checksum to set in the IP packet. If > the IP length is invalid in the header, it returns 0. > It still mentions 0 as a special value, increasing the risk of the defensive user adding "error handling" for a return value of 0.
How about this? The complemented checksum to set in the IP packet. If the IP length is invalid in the header, the return value is undefined. > > > > > > > > > > For the same reason, unlikely() should be added to this > comparison. > > > > > > Maybe yes, but that's another story I think. > > > > Agree. I was just mentioning it so it can be done when modifying the > function anyway. > > > > > > > > > Otherwise, > > > > > > > > Acked-by: Morten Brørup <m...@smartsharesystems.com> > > > > > >
