Re: [PATCH] selftests: net: veth: check UDP GRO forwarding on forwarded traffic

[Willem de Bruijn <willemdebruijn.kernel@gmail.com>]

Eva Kurchatova wrote:
> The rx-udp-gro-forwarding checks fail with "got 10 packets, expected 1"
> on a host where something has a UDP tunnel socket, a vxlan say, and
> pass on a host where nothing does. Since commit 36707061d6ba ("udp:
> allow forwarding of plain (non-fraglisted) UDP GRO packets") the
> feature aggregates only datagrams GRO finds no socket for, and GRO
> looks the socket up only once a tunnel socket exists on the host; the
> checks send to a socket in the receiving namespace, so they pass only
> while nothing looks it up.
> 
> Let the destination forward the datagrams to a receiver in a namespace
> behind it: no local socket is found there, tunnel or not, and the
> checks count what the destination receives as before.
> 
> Fixes: 1c3cadbe0242 ("self-tests: add veth tests")
> Suggested-by: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
> Link: https://lore.kernel.org/netdev/CAF=yD-LZSec9g_0bBgrcQvq2OO1BrxMSRHH=uU7eamCmWcTO_A@mail.gmail.com/
> Signed-off-by: Eva Kurchatova <eva.kurchatova@virtuozzo.com>
> ---
>  tools/testing/selftests/net/veth.sh | 26 ++++++++++++++++++++++----
>  1 file changed, 22 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/testing/selftests/net/veth.sh b/tools/testing/selftests/net/veth.sh
> index 8b867e0675a7..be7c6b9213a9 100755
> --- a/tools/testing/selftests/net/veth.sh
> +++ b/tools/testing/selftests/net/veth.sh
> @@ -9,12 +9,17 @@ readonly DST=1
>  readonly DST_NAT=100
>  readonly NS_SRC=$BASE$SRC
>  readonly NS_DST=$BASE$DST
> +# The receiver of the GRO checks, behind the destination
> +readonly RCV=3
> +readonly NS_RCV=$BASE$RCV
>  # shellcheck disable=SC2155 # prefer RO variable over return value from cmd
>  readonly YNL="$(dirname "$(readlink -f "$0")")/../../../net/ynl/pyynl/cli.py"
>  
>  # "baremetal" network used for raw UDP traffic
>  readonly BM_NET_V4=192.168.1.
>  readonly BM_NET_V6=2001:db8::
> +# Network between the destination and the receiver
> +readonly RCV_NET_V4=192.168.2.
>  
>  readonly CPUS=`nproc`
>  ret=0
> @@ -26,7 +31,7 @@ cleanup() {
>  	[ -n "${jobs}" ] && kill -1 ${jobs} 2>/dev/null
>  	rm -f $STATS
>  
> -	for ns in $NS_SRC $NS_DST; do
> +	for ns in $NS_SRC $NS_DST $NS_RCV; do
>  		ip netns del $ns 2>/dev/null
>  	done
>  }
> @@ -48,6 +53,17 @@ create_ns() {
>  		ip -n $BASE$ns addr add dev veth$ns $BM_NET_V4$ns/24
>  		ip -n $BASE$ns addr add dev veth$ns $BM_NET_V6$ns/64 nodad
>  	done
> +
> +	# Forwarded, the datagrams find no local socket, whatever tunnel the host has
> +	ip netns add $NS_RCV
> +	ip -n $NS_RCV link set dev lo up
> +	ip link add name fwd$DST type veth peer name fwd$RCV
> +	ip link set dev fwd$DST netns $NS_DST up
> +	ip link set dev fwd$RCV netns $NS_RCV up
> +	ip -n $NS_DST addr add dev fwd$DST $RCV_NET_V4$DST/24
> +	ip -n $NS_RCV addr add dev fwd$RCV $RCV_NET_V4$RCV/24

Similar to the cleanup code above, this can probably reuse the loop in
create_ns?

Also a bit confusing that NS_DST is no longer the dst, but keeps its name
and now there is an additional NS_RCV.

> +	ip netns exec $NS_DST sysctl -wq net.ipv4.ip_forward=1
> +	ip -n $NS_RCV route add default via $RCV_NET_V4$DST
>  }
>  
>  __chk_flag() {
> @@ -134,15 +150,17 @@ chk_gro() {
>  	local msg="$1"
>  	local expected=$2
>  
> -	ip netns exec $BASE$SRC ping -qc 1 $BM_NET_V4$DST >/dev/null
> +	# Taking veth$SRC down drops the route, so set it for every check

What takes this down?

> +	ip -n $NS_SRC route replace ${RCV_NET_V4}0/24 via $BM_NET_V4$DST
> +	ip netns exec $BASE$SRC ping -qc 1 $RCV_NET_V4$RCV >/dev/null
>  	NSTAT_HISTORY=$STATS ip netns exec $NS_DST nstat -n
>  
>  	printf "%-60s" "$msg"
> -	ip netns exec $BASE$DST ./udpgso_bench_rx -C 1000 -R 10 &
> +	ip netns exec $NS_RCV ./udpgso_bench_rx -C 1000 -R 10 &
>  	local spid=$!
>  	sleep 0.1
>  
> -	ip netns exec $NS_SRC ./udpgso_bench_tx -4 -s 13000 -S 1300 -M 1 -D $BM_NET_V4$DST
> +	ip netns exec $NS_SRC ./udpgso_bench_tx -4 -s 13000 -S 1300 -M 1 -D $RCV_NET_V4$RCV
>  	local retc=$?
>  	wait $spid
>  	local rets=$?
> -- 
> 2.56.0
>