diff --git a/kernel/src/syscall/mod.rs b/kernel/src/syscall/mod.rs
index 283cecc..ad8856f 100644
--- a/kernel/src/syscall/mod.rs
+++ b/kernel/src/syscall/mod.rs
@@ -8,6 +8,7 @@ use rcore_memory::VMError;
 use rcore_fs::vfs::{FileType, FsError, INode, Metadata};
 
 use crate::arch::interrupt::TrapFrame;
+use crate::sync::Condvar;
 use crate::process::*;
 use crate::thread;
 use crate::util;
@@ -336,3 +337,21 @@ impl From<VMError> for SysError {
         SysError::EFAULT
     }
 }
+
+
+const SPIN_WAIT_TIMES: usize = 100;
+
+pub fn spin_and_wait(condvars: &[&Condvar], mut action: impl FnMut() -> Option<SysResult>) -> SysResult {
+    for i in 0..SPIN_WAIT_TIMES {
+        if let Some(result) = action() {
+            return result;
+        }
+    }
+    loop {
+        if let Some(result) = action() {
+            return result;
+        }
+        Condvar::wait_any(&condvars);
+    }
+}
+
diff --git a/kernel/src/syscall/net.rs b/kernel/src/syscall/net.rs
index cffff95..b3fd600 100644
--- a/kernel/src/syscall/net.rs
+++ b/kernel/src/syscall/net.rs
@@ -20,6 +20,9 @@ const IPPROTO_IP: usize = 0;
 const IPPROTO_ICMP: usize = 1;
 const IPPROTO_TCP: usize = 6;
 
+const TCP_SENDBUF: usize = 128 * 1024; // 128K
+const TCP_RECVBUF: usize = 128 * 1024;
+
 fn get_ephemeral_port() -> u16 {
     // TODO selects non-conflict high port
     static mut EPHEMERAL_PORT: u16 = 49152;
@@ -45,8 +48,8 @@ pub fn sys_socket(domain: usize, socket_type: usize, protocol: usize) -> SysResu
             SOCK_STREAM => {
                 let fd = proc.get_free_fd();
 
-                let tcp_rx_buffer = TcpSocketBuffer::new(vec![0; 2048]);
-                let tcp_tx_buffer = TcpSocketBuffer::new(vec![0; 2048]);
+                let tcp_rx_buffer = TcpSocketBuffer::new(vec![0; TCP_RECVBUF]);
+                let tcp_tx_buffer = TcpSocketBuffer::new(vec![0; TCP_SENDBUF]);
                 let tcp_socket = TcpSocket::new(tcp_rx_buffer, tcp_tx_buffer);
 
                 let tcp_handle = iface.sockets().add(tcp_socket);
@@ -151,10 +154,18 @@ pub fn sys_getsockopt(
     match level {
         SOL_SOCKET => {
             match optname {
-                SO_SNDBUF | SO_RCVBUF => {
+                SO_SNDBUF => {
+                    proc.memory_set.check_mut_array(optval, 4)?;
+                    unsafe {
+                        *(optval as *mut u32) = TCP_SENDBUF as u32;
+                        *optlen = 4;
+                    }
+                    Ok(0)
+                }
+                SO_RCVBUF => {
                     proc.memory_set.check_mut_array(optval, 4)?;
                     unsafe {
-                        *(optval as *mut u32) = 1024;
+                        *(optval as *mut u32) = TCP_RECVBUF as u32;
                         *optlen = 4;
                     }
                     Ok(0)