sockperf pp udp mode: wrong source ip address in udp response datagrams

[O-ring]

Hello everyone,

I have found a bug with sockperf running a pp test (udp mode).
This is the setup on my linux machine where sockperf is running with this command:

sockperf sr --daemonize

eth0: <BROADCAST,MULTICAST,UP,LOWER_UP>
inet 10.68.64.254/22 brd 10.68.67.255 scope global eth0

eth3: <BROADCAST,MULTICAST,UP,LOWER_UP>
inet 33.56.27.126/28 brd 33.56.27.127 scope global eth3
inet 33.56.27.125/32 scope global eth3

default via 10.68.64.1 dev eth0 metric 1
33.56.27.112/28 dev eth3 proto kernel scope link src 33.56.27.126

If I try to run a pp test from a client with this command:

sockperf pp -m 64 -i 10.68.64.254 --time 10 --full-rtt --mps=max

everything is fine: I can see the correct source and destination ip addresses in the udp datagrams.
Instead if I run this command from the client:

sockperf pp -m 64 -i 33.56.27.126 --time 10 --full-rtt --mps=max

I can see that the sockperf server is sending out the udp reply datagrams with the wrong source ip address: 10.68.64.254 instead of 33.56.27.126

The tcp test mode instead is fine. Indeed running the sockeperf server with this command is a workaround:

sockperf sr -i 33.56.27.126

Would be fine to have this bug fixed.

[igor-ivanov]

@O-ring please try with additional option as --client_ip

[O-ring]

Hello Igor,

Same problem. This is the pcap capture taken on the server:

udp packet from client to server:

17:16:17.995933 IP (tos 0x28, ttl 59, id 55539, offset 0, flags [DF], proto UDP (17), length 92)
10.81.160.56.45096 > 33.56.27.126.11111: UDP, length 64

response udp packet from server to client:

17:16:17.978461 IP (tos 0x0, ttl 64, id 24898, offset 0, flags [DF], proto UDP (17), length 92)
10.68.64.254.11111 > 10.81.160.56.45096: UDP, length 64

As you can see, the running sockperf server is replying with the wrong source ip address.