diff --git a/.github/ISSUE_TEMPLATE/bug-report.yaml b/.github/ISSUE_TEMPLATE/bug-report.yaml
index 8d982d1f9..6d4b0676c 100644
--- a/.github/ISSUE_TEMPLATE/bug-report.yaml
+++ b/.github/ISSUE_TEMPLATE/bug-report.yaml
@@ -65,6 +65,22 @@ body:
         - BSD
     validations:
       required: true
+  - type: input
+    id: os-version
+    attributes:
+      label: OS version
+      description: What's the specific version of OS?
+      placeholder: "Run `uname -srm` command to get the info, for example: Darwin 21.5.0 arm64, Linux 5.4.0-137-generic x86_64"
+    validations:
+      required: true
+  - type: input
+    id: go-version
+    attributes:
+      label: Go version
+      description: What's the specific version of Go?
+      placeholder: "Run `go version` command to get the info, for example: go1.20.5 linux/amd64"
+    validations:
+      required: true
   - type: textarea
     id: logs
     attributes:
diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
index dc36bf2d4..b2c12d4f4 100644
--- a/.github/workflows/codeql.yml
+++ b/.github/workflows/codeql.yml
@@ -8,6 +8,9 @@ on:
       - 1.x
     paths-ignore:
       - '**.md'
+      - '**.yml'
+      - '**.yaml'
+      - '!.github/workflows/codeql.yml'
   pull_request:
     branches:
       - master
@@ -15,6 +18,9 @@ on:
       - 1.x
     paths-ignore:
       - '**.md'
+      - '**.yml'
+      - '**.yaml'
+      - '!.github/workflows/codeql.yml'
   schedule:
     #        ┌───────────── minute (0 - 59)
     #        │  ┌───────────── hour (0 - 23)
diff --git a/.github/workflows/pull-request.yml b/.github/workflows/pull-request.yml
new file mode 100644
index 000000000..f9bf06351
--- /dev/null
+++ b/.github/workflows/pull-request.yml
@@ -0,0 +1,19 @@
+name: Check pull request target
+on:
+  pull_request:
+    types:
+      - opened
+      - reopened
+      - synchronize
+    branches:
+      - master
+jobs:
+  check-branches:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check target branch
+        run: |
+          if [ ${{ github.head_ref }} != "dev" ]; then
+            echo "Only pull requests from dev branch are only allowed to be merged into master branch."
+            exit 1
+          fi
diff --git a/.github/workflows/release-drafter.yaml b/.github/workflows/release-drafter.yml
similarity index 100%
rename from .github/workflows/release-drafter.yaml
rename to .github/workflows/release-drafter.yml
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 5a9b98950..776c3f0f4 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -8,6 +8,9 @@ on:
       - 1.x
     paths-ignore:
       - '**.md'
+      - '**.yml'
+      - '**.yaml'
+      - '!.github/workflows/test.yml'
   pull_request:
     branches:
       - master
@@ -15,6 +18,9 @@ on:
       - 1.x
     paths-ignore:
       - '**.md'
+      - '**.yml'
+      - '**.yaml'
+      - '!.github/workflows/test.yml'
 
 env:
   GO111MODULE: on
diff --git a/.github/workflows/test_gc_opt.yml b/.github/workflows/test_gc_opt.yml
index d81287b78..c18da9b61 100644
--- a/.github/workflows/test_gc_opt.yml
+++ b/.github/workflows/test_gc_opt.yml
@@ -8,6 +8,9 @@ on:
       - 1.x
     paths-ignore:
       - '**.md'
+      - '**.yml'
+      - '**.yaml'
+      - '!.github/workflows/test_gc_opt.yml'
   pull_request:
     branches:
       - master
@@ -15,6 +18,9 @@ on:
       - 1.x
     paths-ignore:
       - '**.md'
+      - '**.yml'
+      - '**.yaml'
+      - '!.github/workflows/test_gc_opt.yml'
 
 env:
   GO111MODULE: on
diff --git a/.github/workflows/test_poll_opt.yml b/.github/workflows/test_poll_opt.yml
index 665077ee9..8f1337d77 100644
--- a/.github/workflows/test_poll_opt.yml
+++ b/.github/workflows/test_poll_opt.yml
@@ -8,6 +8,9 @@ on:
       - 1.x
     paths-ignore:
       - '**.md'
+      - '**.yml'
+      - '**.yaml'
+      - '!.github/workflows/test_poll_opt.yml'
   pull_request:
     branches:
       - master
@@ -15,6 +18,9 @@ on:
       - 1.x
     paths-ignore:
       - '**.md'
+      - '**.yml'
+      - '**.yaml'
+      - '!.github/workflows/test_poll_opt.yml'
 
 env:
   GO111MODULE: on
diff --git a/.github/workflows/test_poll_opt_gc_opt.yml b/.github/workflows/test_poll_opt_gc_opt.yml
index 7c0a09487..5af9f93aa 100644
--- a/.github/workflows/test_poll_opt_gc_opt.yml
+++ b/.github/workflows/test_poll_opt_gc_opt.yml
@@ -8,6 +8,9 @@ on:
       - 1.x
     paths-ignore:
       - '**.md'
+      - '**.yml'
+      - '**.yaml'
+      - '!.github/workflows/test_poll_opt_gc_opt.yml'
   pull_request:
     branches:
       - master
@@ -15,6 +18,9 @@ on:
       - 1.x
     paths-ignore:
       - '**.md'
+      - '**.yml'
+      - '**.yaml'
+      - '!.github/workflows/test_poll_opt_gc_opt.yml'
 
 env:
   GO111MODULE: on
diff --git a/conn_matrix.go b/conn_matrix.go
index 7293641ab..70ba4affa 100644
--- a/conn_matrix.go
+++ b/conn_matrix.go
@@ -107,6 +107,7 @@ func (cm *connMatrix) delConn(c *conn) {
 		if cm.connCounts[row] == 0 {
 			continue
 		}
+
 		columnMin := -1
 		if row == cgfd.ConnMatrixRow() {
 			columnMin = cgfd.ConnMatrixColumn()
diff --git a/conn_matrix_test.go b/conn_matrix_test.go
index 17487bb50..c081cfa67 100644
--- a/conn_matrix_test.go
+++ b/conn_matrix_test.go
@@ -105,9 +105,8 @@ func testConnMatrix(t *testing.T, n int) {
 			if !ok {
 				t.Fatalf("missing gfd for fd %d", c.fd)
 			}
-			if i != gfd.ConnMatrixRow() || j != gfd.ConnMatrixColumn() {
-				t.Fatalf("unexpected row %d, column %d, expected row %d, column %d",
-					gfd.ConnMatrixRow(), gfd.ConnMatrixColumn(), i, j)
+			if gfd != c.gfd {
+				t.Fatalf("expected gfd: %v, but got gfd: %v", c.gfd, gfd)
 			}
 		}
 	}