INSTALL         | 10 +++++++---
 USAGE           |  2 +-
 USAGE.GNU+Linux |  1 -
 build           |  2 +-
 tapser.c        | 27 +++++++++++++++++++--------

diff --git a/INSTALL b/INSTALL
index 98f7b8ba45886fdca12e495e879e27ff7a66b813994c7adda8307627f6c799ad..548a0b498b1df72aa516ab3a199efbe813147850fff632b963dc5c75103307da 100644
--- a/INSTALL
+++ b/INSTALL
@@ -1,9 +1,13 @@
+    $ ./build -O3
+
+To enable ckecksum support use -DTAPSER_ENABLE_XXH3:
+
     $ curl -L https://api.github.com/repos/Cyan4973/xxHash/tarball/v0.8.3 | tar xf -
     $ cp Cyan4973-xxHash-e626a72/xxhash.[ch] .
-    $ ./build -O3
+    $ ./build -O3 -DTAPSER_ENABLE_XXH3 -I. xxhash.c
 
 Look in xxhash.h for its related options.
 
-To enable Zstandard compression:
+To enable Zstandard compression use -DTAPSER_ENABLE_ZSTD:
 
-    $ ./build -DTAPSER_ENABLE_ZSTD -lzstd
+    $ ./build -O3 -DTAPSER_ENABLE_ZSTD $(pkgconf --cflags --libs libzstd)
diff --git a/USAGE b/USAGE
index 8a9a7b5a58d41ea145d3befa8b7b02e39b3c4867306380b2144ff932ab4faf90..1d4baa638eee5094c06437512f47d7e0590bc51f599784ecd142c87146e2bd44 100644
--- a/USAGE
+++ b/USAGE
@@ -6,6 +6,6 @@ created. TAPSER_IF environment variable holds its name.
 
 -t option switches from TAP to TUN mode of operation.
 
--n option disables checksum usage, using plain SLIP.
+-c option enables checksum usage.
 
 -z enabled Zstandard compression. That disables checksumming.
diff --git a/USAGE.GNU+Linux b/USAGE.GNU+Linux
index 9f0d18f9f00665772a4017dc2c1c795249fc13c7cbd2ea3ff7133a690e8f957e..d12eb8ea2cdb38ca9a67b24875b9b2c808a979444c5c5da35bfc6376bc5d07ba 100644
--- a/USAGE.GNU+Linux
+++ b/USAGE.GNU+Linux
@@ -1,5 +1,4 @@
 Network interface is created with the specified name.
-Reusing is currently not done.
 
     # tapser -u '
         ip link set up dev $TAPSER_IF
diff --git a/build b/build
index 3a215ad4d703d644545379103afc92c9860f402fc16dd56e99a4ef27d715100e..6f79843d002d1b7bbef12496297fbf3db120f4ee638abccf7f14ff1715dce68b 100755
--- a/build
+++ b/build
@@ -7,5 +7,5 @@     -ffunction-sections -fdata-sections \
     $CFLAGS \
     -D_DEFAULT_SOURCE \
     -DXXH_NO_STREAM \
-    $@ tapser.c xxhash.c \
+    $@ tapser.c \
     $LDFLAGS $LDLIBS -Wl,--gc-sections
diff --git a/tapser.c b/tapser.c
index 4e027ba4367b74c2f7f6ed80b2e8b7919f8d4f78451bb1d15451704fc2acbd80..0b5260dac6e3cf7e1eba0d905c1a101ee8a89b1d7c9c6e52f50019df2d28cd7a 100644
--- a/tapser.c
+++ b/tapser.c
@@ -21,7 +21,9 @@ #include <net/if_tap.h>
 #include <net/if_tun.h>
 #endif // __linux__
 
-#include "xxhash.h"
+#ifdef TAPSER_ENABLE_XXH3
+#include <xxhash.h>
+#endif // TAPSER_ENABLE_XXH3
 
 #ifdef TAPSER_ENABLE_ZSTD
 #include <zstd.h>
@@ -139,22 +141,22 @@ static void
 usage()
 {
     // clang-format off
-    fputs("Usage: tapser [-n] [-z] [-s speed] [-u cmd] [-d cmd] /dev/ttyX tapX\n", stderr);
+    fputs("Usage: tapser [-c] [-z] [-s speed] [-u cmd] [-d cmd] /dev/ttyX tapX\n", stderr);
     fputs("tapX is desirable name for the newly created TUN/TAP interface on GNU/Linux\n", stderr);
     fputs("tapX can be full path to already existing /dev/{tap,tun}X device on *BSD\n", stderr);
     fputs("tapX can be /dev/{tap,tun} to create new one on *BSD\n", stderr);
-    fputs("-n disables checksum usage\n", stderr);
+    fputs("-c enables checksums\n", stderr);
     fputs("-s sets the speed of TTY, by default to 115200\n", stderr);
     fputs("-u specifies shell command to be run after interface is ready\n", stderr);
     fputs("-d specifies shell command to be run when we exit\n", stderr);
-    fputs("-z enable compression\n", stderr);
+    fputs("-z enable compression (and disable checksums)\n", stderr);
     // clang-format on
 }
 
 int
 main(int argc, char *argv[])
 {
-    bool useCsum = true;
+    bool useCsum = false;
     bool isTUN = false;
     bool compress = false;
 #ifdef TAPSER_ENABLE_ZSTD
@@ -170,13 +172,18 @@     int exitCode = EXIT_FAILURE;
     extern char *optarg;
     extern int optind;
     for (int c = 0;;) {
-        c = getopt(argc, argv, "ns:u:d:tz");
+        c = getopt(argc, argv, "cs:u:d:tz");
         if (c == -1) {
             break;
         }
         switch (c) {
-        case 'n':
-            useCsum = false;
+        case 'c':
+#ifdef TAPSER_ENABLE_XXH3
+            useCsum = true;
+#else // TAPSER_ENABLE_XXH3
+            fprintf(stderr, "xxh3 was not enabled during build\n");
+            goto Free;
+#endif // TAPSER_ENABLE_XXH3
             break;
         case 's':
             errno = 0;
@@ -300,11 +307,13 @@                     fprintf(stderr, "> %zu\t!IP: %d\n", pktLen, src[0]);
                     continue;
                 }
             }
+#ifdef TAPSER_ENABLE_XXH3
             if (useCsum) {
                 XXH64_canonicalFromHash(
                     (XXH64_canonical_t *)(src + srcLen), XXH3_64bits(src, srcLen));
                 srcLen += 8;
             }
+#endif // TAPSER_ENABLE_XXH3
 #ifdef TAPSER_ENABLE_ZSTD
             if (compress) {
                 const size_t s =
@@ -402,6 +411,7 @@                     goto PktDone;
                 }
                 const size_t rxLenOrig = rxLen - (isTUN ? TUNHdrLen : 0);
                 unsigned char *src = rx;
+#ifdef TAPSER_ENABLE_XXH3
                 if (useCsum) {
                     if (rxLen < TUNHdrLen + 8) {
                         fprintf(stderr, "< %zu\ttoo short\n", rxLenOrig);
@@ -415,6 +425,7 @@                         goto PktDone;
                     }
                     rxLen -= 8;
                 }
+#endif // TAPSER_ENABLE_XXH3
 #ifdef TAPSER_ENABLE_ZSTD
                 if (compress) {
                     const size_t s = ZSTD_decompressDCtx(