Use a ringbuffer in shared memory to transfer packets from the tapreader thread to...

It's a wonder it ever worked before. The socket that is created is not of a
datagram type, therefore packet boundaries were not preserved, which becomes
a problem as soon as the TAP-Win32 device receives packets in fast succession.

diff --git a/src/mingw/device.c b/src/mingw/device.c
index 1c1c2e66b533d2bc609eb440532edc445bfe35c6..004249ce49f82efc94b9bb0c775cdd7012184770 100644 (file)
--- a/src/mingw/device.c
+++ b/src/mingw/device.c
@@ -45,16 +45,23 @@ static int device_total_out = 0;
 
 extern char *myport;
 
+static struct packetbuf {
+       uint8_t data[MTU];
+       length_t len;
+} *bufs;
+
+static int nbufs = 64;
+
 DWORD WINAPI tapreader(void *bla) {
        int sock, err, status;
        struct addrinfo *ai;
        struct addrinfo hint = {
                .ai_family = AF_UNSPEC,
-               .ai_socktype = SOCK_DGRAM,
-               .ai_protocol = IPPROTO_UDP,
+               .ai_socktype = SOCK_STREAM,
+               .ai_protocol = IPPROTO_TCP,
                .ai_flags = 0,
        };
-       char buf[MTU];
+       unsigned char bufno = 0;
        long len;
        OVERLAPPED overlapped;
 
@@ -67,7 +74,7 @@ DWORD WINAPI tapreader(void *bla) {
                return -1;
        }
 
-       sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
+       sock = socket(ai->ai_family, SOCK_STREAM, IPPROTO_TCP);
 
        freeaddrinfo(ai);
 
@@ -92,7 +99,7 @@ DWORD WINAPI tapreader(void *bla) {
                overlapped.OffsetHigh = 0;
                ResetEvent(overlapped.hEvent);
 
-               status = ReadFile(device_handle, buf, sizeof(buf), &len, &overlapped);
+               status = ReadFile(device_handle, bufs[bufno].data, MTU, &len, &overlapped);
 
                if(!status) {
                        if(GetLastError() == ERROR_IO_PENDING) {
@@ -106,8 +113,11 @@ DWORD WINAPI tapreader(void *bla) {
                        }
                }
 
-               if(send(sock, buf, len, 0) <= 0)
+               bufs[bufno].len = len;
+               if(send(sock, &bufno, 1, 0) <= 0)
                        return -1;
+               if(++bufno >= nbufs)
+                       bufno = 0;
        }
 }
 
@@ -131,9 +141,9 @@ bool setup_device(void)
        struct addrinfo *ai;
        struct addrinfo hint = {
                .ai_family = AF_UNSPEC,
-               .ai_socktype = SOCK_DGRAM,
-               .ai_protocol = IPPROTO_UDP,
-               .ai_flags = 0,
+               .ai_socktype = SOCK_STREAM,
+               .ai_protocol = IPPROTO_TCP,
+               .ai_flags = AI_PASSIVE,
        };
 
        cp();
@@ -228,6 +238,16 @@ bool setup_device(void)
                overwrite_mac = 1;
        }
 
+       /* Set up ringbuffer */
+
+       get_config_int(lookup_config(config_tree, "RingBufferSize"), &nbufs);
+       if(nbufs <= 1)
+               nbufs = 1;
+       else if(nbufs > 256)
+               nbufs = 256;
+       
+       bufs = xmalloc_and_zero(nbufs * sizeof *bufs);
+
        /* Create a listening socket */
 
        err = getaddrinfo(NULL, myport, &hint, &ai);
@@ -237,7 +257,7 @@ bool setup_device(void)
                return false;
        }
 
-       sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
+       sock = socket(ai->ai_family, SOCK_STREAM, IPPROTO_TCP);
 
        if(sock < 0) {
                logger(LOG_ERR, _("System call `%s' failed: %s"), "socket", strerror(errno));
@@ -295,17 +315,18 @@ void close_device(void)
 
 bool read_packet(vpn_packet_t *packet)
 {
-       int lenin;
+       unsigned char bufno;
 
        cp();
 
-       if((lenin = recv(device_fd, packet->data, MTU, 0)) <= 0) {
+       if((recv(device_fd, &bufno, 1, 0)) <= 0) {
                logger(LOG_ERR, _("Error while reading from %s %s: %s"), device_info,
                           device, strerror(errno));
                return false;
        }
        
-       packet->len = lenin;
+       packet->len = bufs[bufno].len;
+       memcpy(packet->data, bufs[bufno].data, bufs[bufno].len);
 
        device_total_in += packet->len;