From b0614beffae0c6590f34d59def2a3044ede27b65 Mon Sep 17 00:00:00 2001
From: wangyu- <wangyucn@gmail.com>
Date: Tue, 31 Oct 2017 19:43:25 -0500
Subject: [PATCH] new function tcp csum

---
 common.cpp | 33 +++++++++++++++++++++++++++++++++
 common.h   |  8 ++++++++
 misc.cpp   | 22 +++++++++++++++++-----
 misc.h     |  4 ++++
 4 files changed, 62 insertions(+), 5 deletions(-)

diff --git a/common.cpp b/common.cpp
index eccd4d8..2af6699 100644
--- a/common.cpp
+++ b/common.cpp
@@ -260,6 +260,39 @@ unsigned short csum(const unsigned short *ptr,int nbytes) {
 
     return(answer);
 }
+
+
+unsigned short tcp_csum(const pseudo_header & ph,const unsigned short *ptr,int nbytes) {//works both for big and little endian
+
+	register long sum;
+    unsigned short oddbyte;
+    register short answer;
+
+    sum=0;
+	unsigned short * tmp= (unsigned short *)&ph;
+	for(int i=0;i<6;i++)
+	{
+		sum+=*tmp++;
+	}
+
+
+    while(nbytes>1) {
+        sum+=*ptr++;
+        nbytes-=2;
+    }
+    if(nbytes==1) {
+        oddbyte=0;
+        *((u_char*)&oddbyte)=*(u_char*)ptr;
+        sum+=oddbyte;
+    }
+
+    sum = (sum>>16)+(sum & 0xffff);
+    sum = sum + (sum>>16);
+    answer=(short)~sum;
+
+    return(answer);
+}
+
 int set_buf_size(int fd,int socket_buf_size,int force_socket_buf)
 {
 	if(force_socket_buf)
diff --git a/common.h b/common.h
index ee4267e..403b0e4 100644
--- a/common.h
+++ b/common.h
@@ -176,6 +176,13 @@ struct fd_info_t
 	ip_port_t ip_port;
 };
 
+struct pseudo_header {
+    u_int32_t source_address;
+    u_int32_t dest_address;
+    u_int8_t placeholder;
+    u_int8_t protocol;
+    u_int16_t tcp_length;
+};
 
 u64_t get_current_time();
 u64_t get_current_time_us();
@@ -209,6 +216,7 @@ void setnonblocking(int sock);
 int set_buf_size(int fd,int socket_buf_size,int force_socket_buf=0);
 
 unsigned short csum(const unsigned short *ptr,int nbytes);
+unsigned short tcp_csum(const pseudo_header & ph,const unsigned short *ptr,int nbytes);
 
 void  signal_handler(int sig);
 int numbers_to_char(id_t id1,id_t id2,id_t id3,char * &data,int &len);
diff --git a/misc.cpp b/misc.cpp
index c8182d2..c387599 100644
--- a/misc.cpp
+++ b/misc.cpp
@@ -48,7 +48,9 @@ char tun_dev[100]="";
 
 int keep_reconnect=0;
 
+int tun_mtu=1500;
 
+int mssfix=1;
 
 
 int from_normal_to_fec(conn_info_t & conn_info,char *data,int len,int & out_n,char **&out_arr,int *&out_len,my_time_t *&out_delay)
@@ -571,6 +573,8 @@ void process_arg(int argc, char *argv[])
 		{"fifo", required_argument,    0, 1},
 		{"sub-net", required_argument,    0, 1},
 		{"tun-dev", required_argument,    0, 1},
+		{"tun-mtu", required_argument,    0, 1},
+		{"disable-mssfix", no_argument,    0, 1},
 		{"keep-reconnect", no_argument,    0, 1},
 		{NULL, 0, 0, 0}
       };
@@ -886,14 +890,22 @@ void process_arg(int argc, char *argv[])
 			}
 			else if(strcmp(long_options[option_index].name,"tun-dev")==0)
 			{
-				if(optarg!=0)
-				{
-					sscanf(optarg,"%s",tun_dev);
-					mylog(log_info,"tun_dev=%s\n",tun_dev);
-				}
+				sscanf(optarg,"%s",tun_dev);
+				mylog(log_info,"tun_dev=%s\n",tun_dev);
+
 				mylog(log_info,"running at tun-dev mode\n");
 				working_mode=tun_dev_mode;
 			}
+			else if(strcmp(long_options[option_index].name,"tun-mtu")==0)
+			{
+				sscanf(optarg,"%d",&tun_mtu);
+				mylog(log_warn,"changed tun_mtu,tun_mtu=%d\n",tun_mtu);
+			}
+			else if(strcmp(long_options[option_index].name,"disable-mssfix")==0)
+			{
+				mssfix=0;
+				mylog(log_warn,"mssfix disabled\n");
+			}
 			else
 			{
 				mylog(log_fatal,"unknown option\n");
diff --git a/misc.h b/misc.h
index 7ad236b..91322fa 100644
--- a/misc.h
+++ b/misc.h
@@ -48,6 +48,10 @@ extern int delay_capacity;
 
 extern int keep_reconnect;
 
+extern int tun_mtu;
+
+extern int mssfix;
+
 
 int from_normal_to_fec(conn_info_t & conn_info,char *data,int len,int & out_n,char **&out_arr,int *&out_len,my_time_t *&out_delay);
 int from_fec_to_normal(conn_info_t & conn_info,char *data,int len,int & out_n,char **&out_arr,int *&out_len,my_time_t *&out_delay);