diff --git a/Makefile b/Makefile
index ad18a59..10668ff 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-CFLAGS=-std=c99 -fsanitize=address -fno-omit-frame-pointer
+CFLAGS=-std=c99 -g -fsanitize=address -fno-omit-frame-pointer
 
 glorytun:
 
diff --git a/common.h b/common.h
index 73b9cc4..fcb4507 100644
--- a/common.h
+++ b/common.h
@@ -4,22 +4,113 @@
 #define _GNU_SOURCE
 #endif
 
+#include <stdlib.h>
+#include <stdint.h>
 #include <unistd.h>
 #include <errno.h>
 
 #define COUNT(x) (sizeof(x)/sizeof(x[0]))
 
-static inline size_t str_cpy (char *dst, char *src, size_t n)
+#define ALIGN_SIZE     (1<<4)
+#define ALIGN_MASK     (ALIGN_SIZE-1)
+
+#define ALIGN(x)       (((x)+ALIGN_MASK)&~ALIGN_MASK)
+#define ALIGN_DOWN(x)  ((x)&~ALIGN_MASK)
+
+#define PALIGN(x)      ((void *)ALIGN((size_t)(x)))
+#define PALIGN_DOWN(x) ((void *)ALIGN_DOWN((size_t)(x)))
+
+static inline void byte_set (void *dst, const char value, size_t size)
+{
+    if (!dst)
+        return;
+
+    char *restrict d = dst;
+
+    while (size--)
+        *d++ = value;
+}
+
+static inline void byte_copy (void *dst, const void *src, size_t size)
+{
+    if (!dst || !src)
+        return;
+
+    char *restrict d = dst;
+    const char *restrict s = src;
+
+    while (size--)
+        *d++ = *s++;
+}
+
+static inline size_t str_cpy (char *dst, const char *src, size_t len)
 {
     if (!dst || !src)
         return 0;
 
     size_t i;
 
-    for (i=0; i<n && src[i]; i++)
+    for (i=0; i<len && src[i]; i++)
         dst[i] = src[i];
 
     dst[i] = 0;
 
     return i;
 }
+
+typedef struct buffer buffer_t;
+
+struct buffer {
+    uint8_t *data;
+    uint8_t *read;
+    uint8_t *write;
+    uint8_t *end;
+};
+
+static inline void buffer_setup (buffer_t *buffer, void *data, size_t size)
+{
+    if (!data)
+        data = malloc(ALIGN(size));
+
+    buffer->data  = data;
+    buffer->read  = data;
+    buffer->write = data;
+    buffer->end   = data;
+    buffer->end  += size;
+}
+
+static inline void buffer_format (buffer_t *buffer)
+{
+    buffer->write = buffer->data;
+    buffer->read  = buffer->data;
+}
+
+static inline size_t buffer_size (buffer_t *buffer)
+{
+    return buffer->end-buffer->data;
+}
+
+static inline size_t buffer_write_size (buffer_t *buffer)
+{
+    return buffer->end-buffer->write;
+}
+
+static inline size_t buffer_read_size (buffer_t *buffer)
+{
+    return buffer->write-buffer->read;
+}
+
+static inline void buffer_shift (buffer_t *buffer)
+{
+    if (buffer->read==buffer->write) {
+        buffer_format(buffer);
+    } else {
+        const uint8_t *src = PALIGN_DOWN(buffer->read);
+        const size_t size = ALIGN(buffer->write-src);
+        if (buffer->data+size<src) {
+            byte_copy(buffer->data, src, size);
+            buffer->read  -= src-buffer->data;
+            buffer->write -= src-buffer->data;
+        }
+    }
+}
diff --git a/glorytun.c b/glorytun.c
index 540ee8c..beddff3 100644
--- a/glorytun.c
+++ b/glorytun.c
@@ -42,7 +42,8 @@ static int gt_open_tun (char *name)
     return fd;
 }
 
-static void gt_sa_stop (int sig) {
+static void gt_sa_stop (int sig)
+{
     switch (sig) {
     case SIGINT:
     case SIGTERM:
@@ -65,6 +66,54 @@ static int gt_set_signal (void)
     sigaction(SIGPIPE, &sa, NULL);
 }
 
+static inline int buffer_read_fd (buffer_t *buffer, int fd)
+{
+    buffer_shift(buffer);
+
+    size_t size = buffer_write_size(buffer);
+
+    if (!size)
+        return -1;
+
+    ssize_t ret = read(fd, buffer->write, size);
+
+    if (ret==-1) {
+        if (errno==EAGAIN || errno==EINTR)
+            return -1;
+        if (errno)
+            printf("read: %m\n");
+        return 0;
+    }
+
+    buffer->write += ret;
+
+    return 1;
+}
+
+static inline int buffer_write_fd (buffer_t *buffer, int fd)
+{
+    size_t size = buffer_read_size(buffer);
+
+    if (!size)
+        return -1;
+
+    ssize_t ret = write(fd, buffer->read, size);
+
+    if (ret==-1) {
+        if (errno==EAGAIN || errno==EINTR)
+            return -1;
+        if (errno)
+            printf("read: %m\n");
+        return 0;
+    }
+
+    buffer->read += ret;
+
+    buffer_shift(buffer);
+
+    return 1;
+}
+
 int main (int argc, char **argv)
 {
     gt_set_signal();
@@ -78,6 +127,9 @@ int main (int argc, char **argv)
         { .fd = tun_fd, .events = POLLIN },
     };
 
+    buffer_t input;
+    buffer_setup(&input, NULL, 256*1024);
+
     while (running) {
         int ret = poll(fds, COUNT(fds), 0);
 
@@ -92,9 +144,13 @@ int main (int argc, char **argv)
             continue;
 
         if (fds[0].revents & POLLIN) {
-            printf("POLLIN!\n");
+            int read_ret = buffer_read_fd(&input, fds[0].fd);
+            printf("read %zu\n", buffer_read_size(&input));
+            buffer_format(&input);
         }
     }
 
+    free(input.data);
+
     return 0;
 }