Re: [PATCH v2 5/6] net: add smaller IPv4 cksum function for simple cases

[David Marchand <david.marchand@redhat.com>]

Hello Bruce,

On Fri, Oct 25, 2024 at 6:51 PM Bruce Richardson
<bruce.richardson@intel.com> wrote:
>
> There are multiple instances in the DPDK app folder where we set up an
> IP header and then compute the checksum field by direct addition of
> nine uint16_t values in the header (20 bytes less the cksum field).
> The existing rte_ip.h checksum function is more general than necessary
> here and requires that the checksum field is already set to zero -
> rather than having it skipped.
>
> Fix the code duplication present in the apps by creating a new
> rte_ipv4_cksum_simple function - taking the code from the existing
> testpmd icmpecho.c file - and using that in app/test, testpmd and
> testeventdev.
>
> Within that new function, we can adjust slightly how the typecasting to
> uint16_t is done, and thereby ensure that the app can all be compiled
> without -Wno-address-of-packed-member compiler flag.
>
> Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
> Acked-by: Stephen Hemminger <stephen@networkplumber.org>
> Acked-by: Morten Brørup <mb@smartsharesystems.com>

This added function triggers a build error with OVS because of -Wcast-align:
https://github.com/david-marchand/ovs/actions/runs/11401635820/job/32273090691#step:12:514

libtool: compile: env REAL_CC=gcc "CHECK=sparse -Wsparse-error -I
./include/sparse -I ./include -m64 -I /usr/local/include -I
/usr/include/x86_64-linux-gnu " cgcc -target=x86_64
-target=host_os_specs -D__MMX__=1 -D__MMX_WITH_SSE__=1
-D__SSE2_MATH__=1 -D__SSE_MATH__=1 -D__SSE__=1 -D__SSE2__=1
-DHAVE_CONFIG_H -I. -I ./include -I ./include -I ./lib -I ./lib
-Wstrict-prototypes -Wall -Wextra -Wno-sign-compare -Wpointer-arith
-Wformat -Wformat-security -Wswitch-enum -Wunused-parameter
-Wbad-function-cast -Wcast-align -Wstrict-prototypes
-Wold-style-definition -Wmissing-prototypes
-Wmissing-field-initializers -fno-strict-aliasing -Wswitch-bool
-Wlogical-not-parentheses -Wsizeof-array-argument -Wbool-compare
-Wshift-negative-value -Wduplicated-cond -Wshadow
-Wmultistatement-macros -Wcast-align=strict -mssse3
-I/home/runner/work/ovs/ovs/dpdk-dir/include -include rte_config.h
-mrtm -Werror -D_FILE_OFFSET_BITS=64 -g -O2 -MT lib/ofp-protocol.lo
-MD -MP -MF lib/.deps/ofp-protocol.Tpo -c lib/ofp-protocol.c -o
lib/ofp-protocol.o
In file included from /home/runner/work/ovs/ovs/dpdk-dir/include/rte_ip.h:9,
from /home/runner/work/ovs/ovs/dpdk-dir/include/rte_flow.h:25,
from lib/netdev-dpdk.h:30,
from lib/dp-packet.h:30,
from lib/ofp-print.c:34:
/home/runner/work/ovs/ovs/dpdk-dir/include/rte_ip4.h: In function
‘rte_ipv4_cksum_simple’:
/home/runner/work/ovs/ovs/dpdk-dir/include/rte_ip4.h:191:17: error:
cast increases required alignment of target type [-Werror=cast-align]
191 | v16_h = (const unaligned_uint16_t *)&ipv4_hdr->version_ihl;
| ^
cc1: all warnings being treated as errors
make[1]: *** [Makefile:4736: lib/ofp-packet.lo] Error 1
make[1]: *** Waiting for unfinished jobs....
cc1: all warnings being treated as errors
make[1]: *** [Makefile:4736: lib/ofp-print.lo] Error 1
make[1]: Leaving directory '/home/runner/work/ovs/ovs'
make: *** [Makefile:3110: all] Error 2



-- 
David Marchand