bridge: fix IPv6 address order assumption in test

[yushoyamaguchi]

Summary

• checkBridgeIPs in the "ensure bridge address" test assumed that AddrList returns same-scope IPv6 addresses in reverse insertion order (newest first), and checked addrs[0]/addrs[1] by index.
• Replace index-based checks with Gomega's ContainElement so the test verifies presence of both addresses without assuming order.

Root cause

Linux kernel v7.0 changed the insertion order for same-scope IPv6 addresses in ipv6_link_dev_addr .
torvalds/linux@cb3de96eea66

Our test was written against v6.x prepend behavior and passed in CI (which runs on a v6.x kernel).
On v7.0+ kernels, AddrList returns addresses in insertion order, causing the index-based checks to fail.

[yushoyamaguchi]

The result of the test in kernel v7.0

ubuntu@yamaguchi-cilium-dev:~/yusho/cni-plugins$ uname -r
7.0.0-14-generic
ubuntu@yamaguchi-cilium-dev:~/yusho/cni-plugins$ sudo go test ./plugins/main/bridge/ --ginkgo.focus="ensure bridge address" -v
=== RUN   TestBridge
Running Suite: plugins/main/bridge - /home/ubuntu/yusho/cni-plugins/plugins/main/bridge
=======================================================================================
Random Seed: 1779542981

Will run 21 of 317 specs
SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS••
------------------------------
• [FAILED] [0.007 seconds]
bridge Operations [It] [0.1.0] (2) ensure bridge address
/home/ubuntu/yusho/cni-plugins/plugins/main/bridge/bridge_test.go:2222

  [FAILED] Expected
      <string>: 2001:db8:1:2::1/64
  to equal
      <string>: fd00:1234::1/64
  In [It] at: /home/ubuntu/yusho/cni-plugins/plugins/main/bridge/bridge_test.go:2259 @ 05/23/26 13:29:41.685
------------------------------
••
------------------------------
• [FAILED] [0.004 seconds]
bridge Operations [It] [0.2.0] (2) ensure bridge address
/home/ubuntu/yusho/cni-plugins/plugins/main/bridge/bridge_test.go:2222

  [FAILED] Expected
      <string>: 2001:db8:1:2::1/64
  to equal
      <string>: fd00:1234::1/64
  In [It] at: /home/ubuntu/yusho/cni-plugins/plugins/main/bridge/bridge_test.go:2259 @ 05/23/26 13:29:41.706
------------------------------
••
------------------------------
• [FAILED] [0.003 seconds]
bridge Operations [It] [0.3.0] (2) ensure bridge address
/home/ubuntu/yusho/cni-plugins/plugins/main/bridge/bridge_test.go:2222

  [FAILED] Expected
      <string>: 2001:db8:1:2::1/64
  to equal
      <string>: fd00:1234::1/64
  In [It] at: /home/ubuntu/yusho/cni-plugins/plugins/main/bridge/bridge_test.go:2259 @ 05/23/26 13:29:41.715
------------------------------
••
------------------------------
• [FAILED] [0.003 seconds]
bridge Operations [It] [0.3.1] (2) ensure bridge address
/home/ubuntu/yusho/cni-plugins/plugins/main/bridge/bridge_test.go:2222

  [FAILED] Expected
      <string>: 2001:db8:1:2::1/64
  to equal
      <string>: fd00:1234::1/64
  In [It] at: /home/ubuntu/yusho/cni-plugins/plugins/main/bridge/bridge_test.go:2259 @ 05/23/26 13:29:41.724
------------------------------
••
------------------------------
• [FAILED] [0.006 seconds]
bridge Operations [It] [0.4.0] (2) ensure bridge address
/home/ubuntu/yusho/cni-plugins/plugins/main/bridge/bridge_test.go:2222

  [FAILED] Expected
      <string>: 2001:db8:1:2::1/64
  to equal
      <string>: fd00:1234::1/64
  In [It] at: /home/ubuntu/yusho/cni-plugins/plugins/main/bridge/bridge_test.go:2259 @ 05/23/26 13:29:41.804
------------------------------
••
------------------------------
• [FAILED] [0.004 seconds]
bridge Operations [It] [1.0.0] (2) ensure bridge address
/home/ubuntu/yusho/cni-plugins/plugins/main/bridge/bridge_test.go:2222

  [FAILED] Expected
      <string>: 2001:db8:1:2::1/64
  to equal
      <string>: fd00:1234::1/64
  In [It] at: /home/ubuntu/yusho/cni-plugins/plugins/main/bridge/bridge_test.go:2259 @ 05/23/26 13:29:41.825
------------------------------
••
------------------------------
• [FAILED] [0.003 seconds]
bridge Operations [It] [1.1.0] (2) ensure bridge address
/home/ubuntu/yusho/cni-plugins/plugins/main/bridge/bridge_test.go:2222

  [FAILED] Expected
      <string>: 2001:db8:1:2::1/64
  to equal
      <string>: fd00:1234::1/64
  In [It] at: /home/ubuntu/yusho/cni-plugins/plugins/main/bridge/bridge_test.go:2259 @ 05/23/26 13:29:41.836
------------------------------
SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS

Summarizing 7 Failures:
  [FAIL] bridge Operations [It] [0.1.0] (2) ensure bridge address
  /home/ubuntu/yusho/cni-plugins/plugins/main/bridge/bridge_test.go:2259
  [FAIL] bridge Operations [It] [0.2.0] (2) ensure bridge address
  /home/ubuntu/yusho/cni-plugins/plugins/main/bridge/bridge_test.go:2259
  [FAIL] bridge Operations [It] [0.3.0] (2) ensure bridge address
  /home/ubuntu/yusho/cni-plugins/plugins/main/bridge/bridge_test.go:2259
  [FAIL] bridge Operations [It] [0.3.1] (2) ensure bridge address
  /home/ubuntu/yusho/cni-plugins/plugins/main/bridge/bridge_test.go:2259
  [FAIL] bridge Operations [It] [0.4.0] (2) ensure bridge address
  /home/ubuntu/yusho/cni-plugins/plugins/main/bridge/bridge_test.go:2259
  [FAIL] bridge Operations [It] [1.0.0] (2) ensure bridge address
  /home/ubuntu/yusho/cni-plugins/plugins/main/bridge/bridge_test.go:2259
  [FAIL] bridge Operations [It] [1.1.0] (2) ensure bridge address
  /home/ubuntu/yusho/cni-plugins/plugins/main/bridge/bridge_test.go:2259

Ran 21 of 317 Specs in 0.187 seconds
FAIL! -- 14 Passed | 7 Failed | 0 Pending | 296 Skipped
--- FAIL: TestBridge (0.20s)
FAIL
FAIL    github.com/containernetworking/plugins/plugins/main/bridge      0.201s
FAIL