diff --git a/vnt/packet/src/lib.rs b/vnt/packet/src/lib.rs
index ac58415..1604c79 100644
--- a/vnt/packet/src/lib.rs
+++ b/vnt/packet/src/lib.rs
@@ -103,9 +103,9 @@ pub fn ipv4_cal_checksum(
     src_ip: &Ipv4Addr,
     dest_ip: &Ipv4Addr,
     protocol: u8,
-    length: u16,
 ) -> u16 {
     use std::io::Cursor;
+    let length = buffer.len();
     let mut sum = 0;
     let src_ip = src_ip.octets();
     sum += u32c(src_ip[0], src_ip[1]);
diff --git a/vnt/packet/src/tcp/tcp.rs b/vnt/packet/src/tcp/tcp.rs
index 3424abf..1be0235 100644
--- a/vnt/packet/src/tcp/tcp.rs
+++ b/vnt/packet/src/tcp/tcp.rs
@@ -134,7 +134,6 @@ impl<B: AsRef<[u8]>> TcpPacket<B> {
             &self.source_ip,
             &self.destination_ip,
             6,
-            self.buffer.as_ref().len() as u16,
         )
     }
     pub fn urgent_pointer(&self) -> u16 {
diff --git a/vnt/packet/src/udp/udp.rs b/vnt/packet/src/udp/udp.rs
index 917ae39..9aedce1 100644
--- a/vnt/packet/src/udp/udp.rs
+++ b/vnt/packet/src/udp/udp.rs
@@ -102,7 +102,6 @@ impl<B: AsRef<[u8]>> UdpPacket<B> {
             &self.source_ip,
             &self.destination_ip,
             17,
-            self.length(),
         )
     }
 }