ubuntu_kernel_selftests:net:udpgro_fwd.sh: udpgso_bench_tx: sendmsg: Connection refused

This is from ADT testing (amd64) but I believe I occasionally saw this before. It feels like sometimes the receiver does not get ready before the transmission starts. IIRC this goes away when re-trying.

02:52:31 DEBUG| [stdout] # selftests: net: udpgro_fwd.sh
02:52:31 DEBUG| [stdout] # IPv4
02:52:31 DEBUG| [stdout] # No GRO ok
02:52:32 DEBUG| [stdout] # GRO frag list ok
02:52:32 DEBUG| [stdout] # GRO fwd ok
02:52:33 DEBUG| [stdout] # UDP fwd perf udp rx: 333 MB/s 271894 calls/s
02:52:33 DEBUG| [stdout] # udp tx: 378 MB/s 6422 calls/s 6422 msg/s
02:52:34 DEBUG| [stdout] # udp rx: 383 MB/s 312480 calls/s
02:52:34 DEBUG| [stdout] # udp tx: 383 MB/s 6506 calls/s 6506 msg/s
02:52:35 DEBUG| [stdout] # udp rx: 381 MB/s 310202 calls/s
02:52:35 DEBUG| [stdout] # udp tx: 380 MB/s 6458 calls/s 6458 msg/s
02:52:36 DEBUG| [stdout] # UDP GRO fwd perf udp rx: 344 MB/s 280814 calls/s
02:52:36 DEBUG| [stdout] # udp tx: 389 MB/s 6612 calls/s 6612 msg/s
02:52:37 DEBUG| [stdout] # udp rx: 364 MB/s 297088 calls/s
02:52:37 DEBUG| [stdout] # udp tx: 383 MB/s 6512 calls/s 6512 msg/s
02:52:38 DEBUG| [stdout] # udp rx: 448 MB/s 365435 calls/s
02:52:38 DEBUG| [stdout] # udp tx: 453 MB/s 7686 calls/s 7686 msg/s
02:52:39 DEBUG| [stdout] # GRO frag list over UDP tunnel ok
02:52:39 DEBUG| [stdout] # GRO fwd over UDP tunnel ok
02:52:39 DEBUG| [stdout] # UDP tunnel fwd perf ./udpgso_bench_tx: sendmsg: Connection refused
02:52:39 DEBUG| [stdout] # fail client exit code 1, server 0
02:52:40 DEBUG| [stdout] # UDP tunnel GRO fwd perf udp rx: 236 MB/s 192389 calls/s
02:52:41 DEBUG| [stdout] # udp tx: 284 MB/s 4826 calls/s 4826 msg/s
02:52:41 DEBUG| [stdout] # udp rx: 295 MB/s 240586 calls/s
02:52:42 DEBUG| [stdout] # udp tx: 306 MB/s 5206 calls/s 5206 msg/s
02:52:42 DEBUG| [stdout] # udp rx: 306 MB/s 249784 calls/s
02:52:43 DEBUG| [stdout] # udp tx: 310 MB/s 5263 calls/s 5263 msg/s
02:52:43 DEBUG| [stdout] # IPv6
02:52:43 DEBUG| [stdout] # No GRO ok
02:52:43 DEBUG| [stdout] # GRO frag list ok
02:52:43 DEBUG| [stdout] # GRO fwd ok
02:52:44 DEBUG| [stdout] # UDP fwd perf udp rx: 82 MB/s 66844 calls/s
02:52:45 DEBUG| [stdout] # udp tx: 334 MB/s 5668 calls/s 5668 msg/s
02:52:45 DEBUG| [stdout] # udp rx: 374 MB/s 305206 calls/s
02:52:46 DEBUG| [stdout] # udp tx: 375 MB/s 6377 calls/s 6377 msg/s
02:52:46 DEBUG| [stdout] # udp rx: 373 MB/s 303948 calls/s
02:52:47 DEBUG| [stdout] # udp tx: 371 MB/s 6299 calls/s 6299 msg/s
02:52:48 DEBUG| [stdout] # UDP GRO fwd perf udp rx: 340 MB/s 277046 calls/s
02:52:48 DEBUG| [stdout] # udp tx: 389 MB/s 6601 calls/s 6601 msg/s
02:52:49 DEBUG| [stdout] # udp rx: 390 MB/s 318311 calls/s
02:52:49 DEBUG| [stdout] # udp tx: 391 MB/s 6639 calls/s 6639 msg/s
02:52:50 DEBUG| [stdout] # udp rx: 396 MB/s 322528 calls/s
02:52:50 DEBUG| [stdout] # udp tx: 406 MB/s 6891 calls/s 6891 msg/s
02:52:50 DEBUG| [stdout] # GRO frag list over UDP tunnel ok
02:52:50 DEBUG| [stdout] # GRO fwd over UDP tunnel ok
02:52:52 DEBUG| [stdout] # UDP tunnel fwd perf udp rx: 93 MB/s 76354 calls/s
02:52:52 DEBUG| [stdout] # udp tx: 257 MB/s 4360 calls/s 4360 msg/s
02:52:53 DEBUG| [stdout] # udp rx: 297 MB/s 241883 calls/s
02:52:53 DEBUG| [stdout] # udp tx: 315 MB/s 5352 calls/s 5352 msg/s
02:52:54 DEBUG| [stdout] # udp rx: 286 MB/s 233207 calls/s
02:52:54 DEBUG| [stdout] # udp tx: 304 MB/s 5172 calls/s 5172 msg/s
02:52:55 DEBUG| [stdout] # UDP tunnel GRO fwd perf udp rx: 267 MB/s 217607 calls/s
02:52:55 DEBUG| [stdout] # udp tx: 297 MB/s 5039 calls/s 5039 msg/s
02:52:56 DEBUG| [stdout] # udp rx: 300 MB/s 244255 calls/s
02:52:56 DEBUG| [stdout] # udp tx: 304 MB/s 5164 calls/s 5164 msg/s
02:52:57 DEBUG| [stdout] # udp rx: 307 MB/s 250399 calls/s
02:52:57 DEBUG| [stdout] # udp tx: 307 MB/s 5221 calls/s 5221 msg/s
02:52:57 DEBUG| [stdout] not ok 1 selftests: net: udpgro_fwd.sh # exit=1