From 504c704ea00aed83857bf2683bfcef08a6b41fc8 Mon Sep 17 00:00:00 2001
From: matsumu-y <72908018+matsumu-y@users.noreply.github.com>
Date: Fri, 1 Apr 2022 20:57:08 +0900
Subject: [PATCH] Enables AMF to accept not-perfect NGAP packets which have not
 0 ASN.1 PER padding bit. (#2)

* Enables AMF to accept not-perfect NGAP packets which have not 0 ASN.1 PER padding bit.

* Use go build -tags skip_padding_check to switch padding check

Default will check padding if value is 0

Co-authored-by: free5gc-org <free5gc.org@gmail.com>
---
 aper.go               | 7 ++++++-
 padding_check.go      | 5 +++++
 skip_padding_check.go | 5 +++++
 3 files changed, 16 insertions(+), 1 deletion(-)
 create mode 100644 padding_check.go
 create mode 100644 skip_padding_check.go

diff --git a/aper.go b/aper.go
index 272df8e..aafd72f 100644
--- a/aper.go
+++ b/aper.go
@@ -131,7 +131,12 @@ func (pd *perBitData) parseAlignBits() error {
 		if val, err := pd.getBitsValue(alignBits); err != nil {
 			return err
 		} else if val != 0 {
-			return fmt.Errorf("Align Bit is not zero")
+			if skipPaddingCheck {
+				perTrace(2, "Align Bit is not zero")
+				perTrace(1, perBitLog(uint64(alignBits), pd.byteOffset, pd.bitsOffset, val))
+			} else {
+				return fmt.Errorf("Align Bit is not zero")
+			}
 		}
 	} else if pd.bitsOffset != 0 {
 		pd.bitCarry()
diff --git a/padding_check.go b/padding_check.go
new file mode 100644
index 0000000..322d488
--- /dev/null
+++ b/padding_check.go
@@ -0,0 +1,5 @@
+// +build !skip_padding_check
+
+package aper
+
+const skipPaddingCheck bool = false
diff --git a/skip_padding_check.go b/skip_padding_check.go
new file mode 100644
index 0000000..45cd9a9
--- /dev/null
+++ b/skip_padding_check.go
@@ -0,0 +1,5 @@
+// +build skip_padding_check
+
+package aper
+
+const skipPaddingCheck bool = true