From e48333d9556b47af6e8856816407786d38b65550 Mon Sep 17 00:00:00 2001
From: angt <angt@users.noreply.github.com>
Date: Tue, 27 Oct 2015 12:55:41 +0100
Subject: [PATCH] Use writev to write in tun

---
 glorytun.c | 69 +++++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 55 insertions(+), 14 deletions(-)

diff --git a/glorytun.c b/glorytun.c
index 11424f6..b269023 100644
--- a/glorytun.c
+++ b/glorytun.c
@@ -16,7 +16,7 @@
 # include <linux/if_tun.h>
 #endif
 
-#define GT_BUFFER_SIZE (256*1024)
+#define GT_BUFFER_SIZE (32*1024)
 
 volatile sig_atomic_t running;
 
@@ -239,6 +239,24 @@ static ssize_t fd_write (int fd, const void *data, size_t size)
     return ret;
 }
 
+static ssize_t fd_writev (int fd, const struct iovec *iov, int count)
+{
+    if (!count)
+        return -2;
+
+    ssize_t ret = writev(fd, iov, count);
+
+    if (ret==-1) {
+        if (errno==EAGAIN || errno==EINTR)
+            return -1;
+        if (errno)
+            perror("write");
+        return 0;
+    }
+
+    return ret;
+}
+
 enum option_type {
     option_flag,
     option_string,
@@ -392,14 +410,19 @@ int main (int argc, char **argv)
             buffer_shift(&tun.recv);
 
             if (fds[0].revents & POLLIN) {
-                size_t size = buffer_write_size(&tun.recv);
-                ssize_t r = fd_read(fds[0].fd, tun.recv.write, size);
+                while (1) {
+                    size_t size = buffer_write_size(&tun.recv);
+                    ssize_t r = fd_read(fds[0].fd, tun.recv.write, size);
 
-                if (!r)
-                    return 2;
+                    if (!r)
+                        return 2;
 
-                if (r>0 && r==get_ip_size(tun.recv.write, size))
-                    tun.recv.write += r;
+                    if (r==-1)
+                        break;
+
+                    if (r>0 && r==get_ip_size(tun.recv.write, size))
+                        tun.recv.write += r;
+                }
             }
 
             if (fds[1].revents & POLLOUT)
@@ -433,11 +456,32 @@ int main (int argc, char **argv)
             if (fds[0].revents & POLLOUT)
                 fds[0].events = POLLIN;
 
-            size_t size = buffer_read_size(&sock.recv);
-            ssize_t ip_size = get_ip_size(sock.recv.read, size);
+            struct iovec iov[16];
+            int count;
 
-            if (ip_size>0 && (size_t)ip_size<=size) {
-                ssize_t r = fd_write(fds[0].fd, sock.recv.read, ip_size);
+            uint8_t *data = sock.recv.read;
+
+            for (count=0; count<COUNT(iov); count++) {
+                size_t size = sock.recv.write-data;
+                ssize_t ip_size = get_ip_size(data, size);
+
+                if (!ip_size)
+                    goto restart;
+
+                if (ip_size==-1)
+                    break;
+
+                if (ip_size>size)
+                    break;
+
+                iov[count].iov_base = data;
+                iov[count].iov_len = ip_size;
+
+                data += ip_size;
+            }
+
+            if (count) {
+                ssize_t r = fd_writev(fds[0].fd, iov, count);
 
                 if (!r)
                     return 2;
@@ -448,9 +492,6 @@ int main (int argc, char **argv)
                 if (r>0)
                     sock.recv.read += r;
             }
-
-            if (!ip_size)
-                goto restart;
         }
 
     restart: