From bc2e65e4821ef4b8fbc33be6c705adfa1c32e02f Mon Sep 17 00:00:00 2001
From: van Hauser <vh@thc.org>
Date: Wed, 29 Apr 2020 15:18:03 +0200
Subject: added afl_network_proxy

---
 examples/afl_network_proxy/README.md | 44 ++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)
 create mode 100644 examples/afl_network_proxy/README.md

(limited to 'examples/afl_network_proxy/README.md')

diff --git a/examples/afl_network_proxy/README.md b/examples/afl_network_proxy/README.md
new file mode 100644
index 00000000..65012601
--- /dev/null
+++ b/examples/afl_network_proxy/README.md
@@ -0,0 +1,44 @@
+# afl-network-proxy
+
+If you want to run afl-fuzz over the network than this is what you need :)
+Note that the impact on fuzzing speed will be huge, expect a loss of 90%.
+
+## When to use this
+
+1. when you have to fuzz a target that has to run on a system that cannot
+   contain the fuzzing output (e.g. /tmp too small and file system is read-only)
+2. when the target instantly reboots on crashes
+3. ... any other reason you would need this
+
+## how to get it running
+
+### on the target
+
+Run `afl-network-server` with your target with the -m and -t values you need.
+Important is the -i parameter which is the TCP port to liste on.
+e.g.:
+```
+$ afl-network-server -i 1111 -m 25M -t 1000 -- /bin/target -f @@
+```
+### on the fuzzing master
+
+Just run afl-fuzz with your normal options, however the target should be
+`afl-network-client` with the IP and PORT of the `afl-network-server` and
+increase the -t value:
+```
+$ afl-fuzz -i in -o out -t 2000+ -- afl-network-client TARGET-IP 1111
+```
+Note the '+' on the -t parameter value. the afl-network-server will take
+care of proper timeouts hence afl-fuzz should not. The '+' increases the timout
+and the value itself should be 500-1000 higher than the one on 
+afl-network-server.
+
+### networking
+
+The TARGET can be an IPv4 or IPv6 address, or a host name that resolves to
+either. Note that also the outgoing interface can be specified with a '%' for
+`afl-network-client`, e.g. `fe80::1234%eth0`.
+
+## how to compile and install
+
+`make && sudo make install`
-- 
cgit 1.4.1


From efa9df24c2a5f97c212a5a22dda19dcbbab0b5de Mon Sep 17 00:00:00 2001
From: van Hauser <vh@thc.org>
Date: Thu, 30 Apr 2020 17:59:59 +0200
Subject: afl-untracer completed

---
 docs/Changelog.md                               |  2 +
 examples/afl_network_proxy/README.md            | 11 +++
 examples/afl_network_proxy/afl-network-client.c | 23 +++---
 examples/afl_network_proxy/afl-network-server.c |  2 +
 examples/afl_untracer/Makefile                  |  2 +-
 examples/afl_untracer/README.md                 |  7 +-
 examples/afl_untracer/afl-untracer.c            | 96 +++++++++++--------------
 examples/afl_untracer/patches.txt               | 23 ++++++
 include/forkserver.h                            |  1 +
 src/afl-forkserver.c                            | 14 ++--
 10 files changed, 106 insertions(+), 75 deletions(-)
 create mode 100644 examples/afl_untracer/patches.txt

(limited to 'examples/afl_network_proxy/README.md')

diff --git a/docs/Changelog.md b/docs/Changelog.md
index faf015c6..565bee72 100644
--- a/docs/Changelog.md
+++ b/docs/Changelog.md
@@ -31,6 +31,8 @@ sending a mail to <afl-users+subscribe@googlegroups.com>.
   - added examples/afl_network_proxy which allows to fuzz a target over the
     network (not fuzzing tcp/ip services but running afl-fuzz on one system
     and the target being on an embedded device)
+  - added examples/afl_untracer which does a binary-only fuzzing with the
+    modifications done in memory
   - added examples/afl_proxy which can be easily used to fuzz and instrument
     non-standard things
   - all:
diff --git a/examples/afl_network_proxy/README.md b/examples/afl_network_proxy/README.md
index 65012601..c33096be 100644
--- a/examples/afl_network_proxy/README.md
+++ b/examples/afl_network_proxy/README.md
@@ -20,6 +20,7 @@ e.g.:
 ```
 $ afl-network-server -i 1111 -m 25M -t 1000 -- /bin/target -f @@
 ```
+
 ### on the fuzzing master
 
 Just run afl-fuzz with your normal options, however the target should be
@@ -42,3 +43,13 @@ either. Note that also the outgoing interface can be specified with a '%' for
 ## how to compile and install
 
 `make && sudo make install`
+
+## Future
+
+It would be much faster and more effective if `afl-network-server` does not
+send the map data back (64kb or more) but the checksum that `afl-fuzz` would
+generate. This change however would make it incompatible with existing
+afl spinoffs.
+
+But in the future this will be implemented and supported as a compile option.
+
diff --git a/examples/afl_network_proxy/afl-network-client.c b/examples/afl_network_proxy/afl-network-client.c
index ede2ff8d..53512286 100644
--- a/examples/afl_network_proxy/afl-network-client.c
+++ b/examples/afl_network_proxy/afl-network-client.c
@@ -175,7 +175,7 @@ static void __afl_start_forkserver(void) {
 
 static u32 __afl_next_testcase(u8 *buf, u32 max_len) {
 
-  s32 status, res = 0xffffff;
+  s32 status, res = 0x0fffffff; // res is a dummy pid
 
   /* Wait for parent by reading from the pipe. Abort if read fails. */
   if (read(FORKSRV_FD, &status, 4) != 4) return 0;
@@ -193,9 +193,7 @@ static u32 __afl_next_testcase(u8 *buf, u32 max_len) {
 
 }
 
-static void __afl_end_testcase(void) {
-
-  int status = 0xffffff;
+static void __afl_end_testcase(int status) {
 
   if (write(FORKSRV_FD + 1, &status, 4) != 4) exit(1);
 
@@ -273,7 +271,7 @@ int main(int argc, char *argv[]) {
   __afl_map_shm();
   __afl_start_forkserver();
 
-  int i = 1, j;
+  int i = 1, j, status, ret;
   // fprintf(stderr, "Waiting for first testcase\n");
   while ((len = __afl_next_testcase(buf, max_len)) > 0) {
 
@@ -281,17 +279,25 @@ int main(int argc, char *argv[]) {
     if (send(s, &len, 4, 0) != 4) PFATAL("sending size data %d failed", len);
     if (send(s, buf, len, 0) != len) PFATAL("sending test data failed");
 
-    int received = 0, ret;
+    int received = 0;
+    while (received < 4 &&
+           (ret = recv(s, &status + received, 4 - received, 0)) > 0)
+      received += ret;
+    if (received != 4)
+      FATAL("did not receive waitpid data (%d, %d)", received, ret);
+    // fprintf(stderr, "Received status\n");
+
+    int received = 0;
     while (received < __afl_map_size &&
            (ret = recv(s, __afl_area_ptr + received, __afl_map_size - received,
                        0)) > 0)
       received += ret;
     if (received != __afl_map_size)
-      FATAL("did not receive valid data (%d, %d)", received, ret);
+      FATAL("did not receive coverage data (%d, %d)", received, ret);
     // fprintf(stderr, "Received coverage\n");
 
     /* report the test case is done and wait for the next */
-    __afl_end_testcase();
+    __afl_end_testcase(status);
     // fprintf(stderr, "Waiting for next testcase %d\n", ++i);
 
   }
@@ -299,4 +305,3 @@ int main(int argc, char *argv[]) {
   return 0;
 
 }
-
diff --git a/examples/afl_network_proxy/afl-network-server.c b/examples/afl_network_proxy/afl-network-server.c
index 1bd37560..2f9f8c8e 100644
--- a/examples/afl_network_proxy/afl-network-server.c
+++ b/examples/afl_network_proxy/afl-network-server.c
@@ -579,6 +579,8 @@ int main(int argc, char **argv_orig, char **envp) {
     // fprintf(stderr, "received %u\n", in_len);
     run_target(fsrv, use_argv, in_data, in_len, 1);
 
+    if (send(s, fsrv->child_status, 4, 0) != 4)
+      FATAL("could not send waitpid data");
     if (send(s, fsrv->trace_bits, fsrv->map_size, 0) != fsrv->map_size)
       FATAL("could not send coverage data");
     // fprintf(stderr, "sent result\n");
diff --git a/examples/afl_untracer/Makefile b/examples/afl_untracer/Makefile
index bfef8fa8..5c525877 100644
--- a/examples/afl_untracer/Makefile
+++ b/examples/afl_untracer/Makefile
@@ -7,4 +7,4 @@ libtestinstr.so:	libtestinstr.c
 	$(CC) -fPIC -o libtestinstr.so -shared libtestinstr.c
 
 clean:
-	rm -f afl-untracer *~ core
+	rm -f afl-untracer libtestinstr.so *~ core
diff --git a/examples/afl_untracer/README.md b/examples/afl_untracer/README.md
index 90798028..d3af0ceb 100644
--- a/examples/afl_untracer/README.md
+++ b/examples/afl_untracer/README.md
@@ -3,9 +3,14 @@
 afl-untracer is an example skeleton file which can easily be used to fuzz
 a closed source library.
 
-It is faster and requires less memory than qemu_mode however it is way
+It requires less memory than qemu_mode however it is way
 more course grained and does not provide interesting features like compcov
 or cmplog.
 
 Read and modify afl-untracer.c then `make` and use it as the afl-fuzz target
 (or even remote via afl-network-proxy).
+
+This idea is based on [UnTracer](https://github.com/FoRTE-Research/UnTracer-AFL)
+and modified by [Trapfuzz](https://github.com/googleprojectzero/p0tools/tree/master/TrapFuzz).
+This implementation is slower because the traps are not patched out with each
+run, but on the other hand gives much better coverage information.
diff --git a/examples/afl_untracer/afl-untracer.c b/examples/afl_untracer/afl-untracer.c
index 420f09a2..4d512356 100644
--- a/examples/afl_untracer/afl-untracer.c
+++ b/examples/afl_untracer/afl-untracer.c
@@ -76,16 +76,9 @@ static u32 use_stdin = 1;
 /* This is were the testcase data is written into */
 static u8 buf[10000];  // this is the maximum size for a test case! set it!
 
-/* if you want to use fork() then uncomment the following line. Otherwise
-   threads are used. The differences:
-                        fork()		pthread()
-  speed	        	slow		fast
-  coverage    		detailed	minimal
-  memory leaks		no problem	an issue                       */
-//#define USE_FORK
-
-/* If you want to have debug output set this to 1 */
-static u32 debug = 1;
+/* If you want to have debug output set this to 1, can also be set with
+   AFL_DEBUG  */
+static u32 debug = 0;
 
 // END STEP 1
 
@@ -130,7 +123,7 @@ void read_library_information() {
   if (debug) fprintf(stderr, "Library list:\n");
   while (fgets(buf, sizeof(buf), f)) {
 
-    if (strstr(buf, " r-xp ")) {
+    if (strstr(buf, " r-x")) {
 
       if (liblist_cnt >= MAX_LIB_COUNT) {
 
@@ -159,9 +152,9 @@ void read_library_information() {
         liblist[liblist_cnt].addr_start = strtoull(b, NULL, 16);
         liblist[liblist_cnt].addr_end = strtoull(m, NULL, 16);
         if (debug)
-          fprintf(stderr, "%s:%x (%x-%x)\n", liblist[liblist_cnt].name,
+          fprintf(stderr, "%s:%x (%lx-%lx)\n", liblist[liblist_cnt].name,
                   liblist[liblist_cnt].addr_end - liblist[liblist_cnt].addr_start,
-                  liblist[liblist_cnt].addr_start, liblist[liblist_cnt].addr_end);
+                  liblist[liblist_cnt].addr_start, liblist[liblist_cnt].addr_end - 1);
         liblist_cnt++;
 
       }
@@ -367,17 +360,13 @@ static u32 __afl_next_testcase(u8 *buf, u32 max_len) {
   if (write(FORKSRV_FD + 1, &pid, 4) != 4) do_exit = 1;
   // fprintf(stderr, "write1 %d\n", do_exit);
 
-  if (!do_exit)
-    __afl_area_ptr[0] = 1;  // otherwise afl-fuzz will exit with NOINST
   return status;
 
 }
 
-static void __afl_end_testcase(void) {
+static void __afl_end_testcase(int status) {
 
-  s32 res = 0xffffff;
-  if (write(FORKSRV_FD + 1, &res, 4) != 4) do_exit = 1;
-  // if (write(FORKSRV_FD + 1, &pid, 4) != 4) do_exit = 1;
+  if (write(FORKSRV_FD + 1, &status, 4) != 4) do_exit = 1;
   // fprintf(stderr, "write2 %d\n", do_exit);
   if (do_exit) exit(0);
 
@@ -455,6 +444,19 @@ void setup_trap_instrumentation() {
 
     // It's an offset, parse it and do the patching.
     unsigned long offset = strtoul(line, NULL, 16);
+
+    // I dont know what it is. /proc/<pid>/maps shows the right start address
+    // and the offsets generated by the python scripts are fine as well.
+    // And loading the library into gdb also shows the offsets generated
+    // by the script are correct. However when loaded via dlopen the first
+    // 0x1000 are skipped ...
+#if defined(__linux__)
+    if (offset >= 0x1000)
+      offset -= 0x1000;
+    else
+      fprintf(stderr, "Warning: offset is < 0x1000: %x\n", offset);
+#endif
+
     if (offset > lib_size)
       FATAL("Invalid offset: 0x%lx. Current library is 0x%zx bytes large",
             offset, lib_size);
@@ -482,11 +484,10 @@ void setup_trap_instrumentation() {
     // this will be ARM and AARCH64
     // for ARM we will need to identify if the code is in thumb or ARM
 #error "non x86_64 not supported yet"
-    //__arm__
+    //__arm__:
     // linux thumb: 0xde01
-    // linux thumb2: 0xf7f0a000
     // linux arm: 0xe7f001f0
-    //__aarch64__
+    //__aarch64__:
     // linux aarch64: 0xd4200000
 #endif
 
@@ -510,6 +511,8 @@ void setup_trap_instrumentation() {
 
 }
 
+/* the signal handler for the traps / debugging interrupts
+   No debug output here because this would cost speed      */
 static void sigtrap_handler(int signum, siginfo_t *si, void *context) {
 
   uint64_t addr;
@@ -525,31 +528,25 @@ static void sigtrap_handler(int signum, siginfo_t *si, void *context) {
 #error "Unsupported platform"
 #endif
 
-  if (debug)
-    fprintf(stderr, "TRAP at context addr = %lx, fault addr = %lx\n", addr,
-            si->si_addr);
+  //fprintf(stderr, "TRAP at context addr = %lx, fault addr = %lx\n", addr, si->si_addr);
 
   // If the trap didn't come from our instrumentation, then we probably will
   // just segfault here
   uint8_t *faultaddr;
-  if (si->si_addr)
+  if (unlikely(si->si_addr))
     faultaddr = (u8 *)si->si_addr - 1;
   else
     faultaddr = (u8 *)addr;
-  // u8 *loc = SHADOW(faultaddr);
-  if (debug)
-    fprintf(stderr, "Shadow location: %p\n", SHADOW(faultaddr));
+  //if (debug) fprintf(stderr, "Shadow location: %p\n", SHADOW(faultaddr));
   uint32_t shadow = *SHADOW(faultaddr);
   uint8_t  orig_byte = shadow & 0xff;
   uint32_t index = shadow >> 8;
 
-  if (debug)
-    fprintf(stderr, "shadow data: %x, orig_byte %02x, index %d\n", shadow,
-            orig_byte, index);
+  //if (debug) fprintf(stderr, "shadow data: %x, orig_byte %02x, index %d\n", shadow, orig_byte, index);
 
   // Index zero is invalid so that it is still possible to catch actual trap
   // instructions in instrumented libraries.
-  if (index == 0) abort();
+  if (unlikely(index == 0)) abort();
 
   // Restore original instruction
   *faultaddr = orig_byte;
@@ -561,6 +558,7 @@ static void sigtrap_handler(int signum, siginfo_t *si, void *context) {
 /* here you need to specify the parameter for the target function */
 static void *(*o_function)(u8 *buf, int len);
 
+/* the MAIN function */
 int main(int argc, char *argv[]) {
 
   pid = getpid();
@@ -579,11 +577,11 @@ int main(int argc, char *argv[]) {
   //         inclusive of the cleanup functions
   //         NOTE: above the main() you have to define the functions!
 
-  /* setup the target */
   void *dl = dlopen("./libtestinstr.so", RTLD_LAZY);
   if (!dl) FATAL("could not find target library");
   o_function = dlsym(dl, "testinstr");
   if (!o_function) FATAL("could not resolve target function from library");
+  if (debug) fprintf(stderr, "Function address: %p\n", o_function);
 
   // END STEP 2
 
@@ -595,42 +593,33 @@ int main(int argc, char *argv[]) {
 
   while (1) {
 
-#ifdef USE_FORK
     if ((pid = fork()) == -1) PFATAL("fork failed");
+
     if (pid) {
 
       u32 status;
       if (waitpid(pid, &status, 0) < 0) exit(1);
+      /* report the test case is done and wait for the next */
+      __afl_end_testcase(status);
 
     } else {
 
-#endif
 
       pid = getpid();
       while ((len = __afl_next_testcase(buf, sizeof(buf))) > 0) {
 
-#ifdef USE_FORK
+        // in this function the fuzz magic happens, this is STEP 3
         fuzz();
-#else
-      if (pthread_create(&__afl_thread, NULL, (void *)fuzz, NULL) != 0)
-        PFATAL("cannot create thread");
-      pthread_join(__afl_thread, NULL);
-#endif
 
-        /* report the test case is done and wait for the next */
-        __afl_end_testcase();
-#ifdef USE_FORK
-        exit(0);
-#endif
+        // we can use _exit which is faster because our target library
+        // was loaded via dlopen and there cannot have deconstructors
+        // registered.
+        _exit(0);
 
       }
 
-#ifdef USE_FORK
-
     }
 
-#endif
-
   }
 
   return 0;
@@ -651,9 +640,4 @@ static void fuzz() {
 
   // END STEP 3
 
-#ifndef USE_FORK
-  pthread_exit(NULL);
-#endif
-
 }
-
diff --git a/examples/afl_untracer/patches.txt b/examples/afl_untracer/patches.txt
new file mode 100644
index 00000000..b3063e3a
--- /dev/null
+++ b/examples/afl_untracer/patches.txt
@@ -0,0 +1,23 @@
+libtestinstr.so:0x2000L
+0x1050L
+0x1063L
+0x106fL
+0x1078L
+0x1080L
+0x10a4L
+0x10b0L
+0x10b8L
+0x10c0L
+0x10c9L
+0x10d7L
+0x10e3L
+0x10f8L
+0x1100L
+0x1105L
+0x111aL
+0x1135L
+0x1143L
+0x114eL
+0x115cL
+0x116aL
+0x116bL
diff --git a/include/forkserver.h b/include/forkserver.h
index 3c473572..7e7784f5 100644
--- a/include/forkserver.h
+++ b/include/forkserver.h
@@ -43,6 +43,7 @@ typedef struct afl_forkserver {
 
   s32 fsrv_pid,                         /* PID of the fork server           */
       child_pid,                        /* PID of the fuzzed program        */
+      child_status,                     /* waitpid result for the child     */
       out_dir_fd;                       /* FD of the lock file              */
 
   s32 out_fd,                           /* Persistent fd for fsrv->out_file */
diff --git a/src/afl-forkserver.c b/src/afl-forkserver.c
index d5a60077..a9e2175d 100644
--- a/src/afl-forkserver.c
+++ b/src/afl-forkserver.c
@@ -790,8 +790,6 @@ fsrv_run_result_t afl_fsrv_run_target(afl_forkserver_t *fsrv, u32 timeout,
   s32 res;
   u32 exec_ms;
 
-  int status = 0;
-
   /* After this memset, fsrv->trace_bits[] are effectively volatile, so we
      must prevent any earlier operations from venturing into that
      territory. */
@@ -821,7 +819,7 @@ fsrv_run_result_t afl_fsrv_run_target(afl_forkserver_t *fsrv, u32 timeout,
 
   if (fsrv->child_pid <= 0) { FATAL("Fork server is misbehaving (OOM?)"); }
 
-  exec_ms = read_timed(fsrv->fsrv_st_fd, &status, 4, timeout, stop_soon_p);
+  exec_ms = read_timed(fsrv->fsrv_st_fd, &fsrv->child_status, 4, timeout, stop_soon_p);
 
   if (exec_ms > timeout) {
 
@@ -830,7 +828,7 @@ fsrv_run_result_t afl_fsrv_run_target(afl_forkserver_t *fsrv, u32 timeout,
 
     kill(fsrv->child_pid, SIGKILL);
     fsrv->last_run_timed_out = 1;
-    if (read(fsrv->fsrv_st_fd, &status, 4) < 4) { exec_ms = 0; }
+    if (read(fsrv->fsrv_st_fd, &fsrv->child_status, 4) < 4) { exec_ms = 0; }
 
   }
 
@@ -862,7 +860,7 @@ fsrv_run_result_t afl_fsrv_run_target(afl_forkserver_t *fsrv, u32 timeout,
 
   }
 
-  if (!WIFSTOPPED(status)) { fsrv->child_pid = 0; }
+  if (!WIFSTOPPED(fsrv->child_status)) { fsrv->child_pid = 0; }
 
   fsrv->total_execs++;
 
@@ -874,9 +872,9 @@ fsrv_run_result_t afl_fsrv_run_target(afl_forkserver_t *fsrv, u32 timeout,
 
   /* Report outcome to caller. */
 
-  if (WIFSIGNALED(status) && !*stop_soon_p) {
+  if (WIFSIGNALED(fsrv->child_status) && !*stop_soon_p) {
 
-    fsrv->last_kill_signal = WTERMSIG(status);
+    fsrv->last_kill_signal = WTERMSIG(fsrv->child_status);
 
     if (fsrv->last_run_timed_out && fsrv->last_kill_signal == SIGKILL) {
 
@@ -891,7 +889,7 @@ fsrv_run_result_t afl_fsrv_run_target(afl_forkserver_t *fsrv, u32 timeout,
   /* A somewhat nasty hack for MSAN, which doesn't support abort_on_error and
      must use a special exit code. */
 
-  if (fsrv->uses_asan && WEXITSTATUS(status) == MSAN_ERROR) {
+  if (fsrv->uses_asan && WEXITSTATUS(fsrv->child_status) == MSAN_ERROR) {
 
     fsrv->last_kill_signal = 0;
     return FSRV_RUN_CRASH;
-- 
cgit 1.4.1


From 1c53bbea52cfecf6c886bb441f1c99c1ae28b0e6 Mon Sep 17 00:00:00 2001
From: van Hauser <vh@thc.org>
Date: Sun, 3 May 2020 14:09:32 +0200
Subject: doubled the speed of afl_network_proxy

---
 examples/afl_network_proxy/Makefile             |  24 +----
 examples/afl_network_proxy/README.md            |  21 ++--
 examples/afl_network_proxy/afl-network-client.c | 119 ++++++++++++++++++--
 examples/afl_network_proxy/afl-network-server.c | 138 +++++++++++++++++++++---
 4 files changed, 246 insertions(+), 56 deletions(-)

(limited to 'examples/afl_network_proxy/README.md')

diff --git a/examples/afl_network_proxy/Makefile b/examples/afl_network_proxy/Makefile
index eeee1178..0b306dde 100644
--- a/examples/afl_network_proxy/Makefile
+++ b/examples/afl_network_proxy/Makefile
@@ -1,22 +1,2 @@
-PREFIX   ?= /usr/local
-BIN_PATH  = $(PREFIX)/bin
-DOC_PATH  = $(PREFIX)/share/doc/afl
-
-PROGRAMS = afl-network-client afl-network-server
-
-all:	$(PROGRAMS)
-
-afl-network-client:	afl-network-client.c
-	$(CC) -I../../include -o afl-network-client afl-network-client.c
-
-afl-network-server:	afl-network-server.c
-	$(CC) -I../../include -o afl-network-server afl-network-server.c ../../src/afl-forkserver.c ../../src/afl-sharedmem.c ../../src/afl-common.c -DBIN_PATH=\"$(BIN_PATH)\"
-
-clean:
-	rm -f $(PROGRAMS) *~ core
-
-install: all
-	install -d -m 755 $${DESTDIR}$(BIN_PATH) $${DESTDIR}$(DOC_PATH)
-	install -m 755 $(PROGRAMS) $${DESTDIR}$(BIN_PATH)
-	install -m 644 README.md $${DESTDIR}$(DOC_PATH)/README.network_proxy.md
-	
\ No newline at end of file
+all:
+	@echo please use GNU make, thanks!
diff --git a/examples/afl_network_proxy/README.md b/examples/afl_network_proxy/README.md
index c33096be..84ebfa48 100644
--- a/examples/afl_network_proxy/README.md
+++ b/examples/afl_network_proxy/README.md
@@ -12,6 +12,14 @@ Note that the impact on fuzzing speed will be huge, expect a loss of 90%.
 
 ## how to get it running
 
+### Compiling
+
+Just type `make` and let the autodetection do everything for you.
+
+Note that compression is supported but currently disabled. It seems that
+sending 64kb of map data over TCP is faster than compressing it with the
+fastest algorithm and options to 112 byte and sending this. Weird.
+
 ### on the target
 
 Run `afl-network-server` with your target with the -m and -t values you need.
@@ -40,16 +48,11 @@ The TARGET can be an IPv4 or IPv6 address, or a host name that resolves to
 either. Note that also the outgoing interface can be specified with a '%' for
 `afl-network-client`, e.g. `fe80::1234%eth0`.
 
+Also make sure your middle value of `/proc/sys/net/ipv4/tcp_rmem` is larger
+than your MAP_SIZE (130kb is a good value). This is the default TCP window
+size value.
+
 ## how to compile and install
 
 `make && sudo make install`
 
-## Future
-
-It would be much faster and more effective if `afl-network-server` does not
-send the map data back (64kb or more) but the checksum that `afl-fuzz` would
-generate. This change however would make it incompatible with existing
-afl spinoffs.
-
-But in the future this will be implemented and supported as a compile option.
-
diff --git a/examples/afl_network_proxy/afl-network-client.c b/examples/afl_network_proxy/afl-network-client.c
index b9cd88f0..94f6bb42 100644
--- a/examples/afl_network_proxy/afl-network-client.c
+++ b/examples/afl_network_proxy/afl-network-client.c
@@ -41,6 +41,10 @@
 #include <netdb.h>
 #include <fcntl.h>
 
+#ifdef USE_DEFLATE
+#include <libdeflate.h>
+#endif
+
 u8 *__afl_area_ptr;
 
 #ifdef __ANDROID__
@@ -206,7 +210,12 @@ int main(int argc, char *argv[]) {
   u8 *            interface, *buf, *ptr;
   s32             s = -1;
   struct addrinfo hints, *hres, *aip;
-  u32             len, max_len = 65536;
+  u32 *           lenptr, max_len = 65536;
+#ifdef USE_DEFLATE
+  u8 *   buf2;
+  u32 *  lenptr1, *lenptr2, buf2_len, compress_len;
+  size_t decompress_len;
+#endif
 
   if (argc < 3 || argc > 4) {
 
@@ -235,8 +244,17 @@ int main(int argc, char *argv[]) {
     if ((__afl_map_size = atoi(ptr)) < 8)
       FATAL("illegal map size, may not be < 8 or >= 2^30: %s", ptr);
 
-  if ((buf = malloc(max_len)) == NULL)
-    PFATAL("can not allocate %u memory", max_len);
+  if ((buf = malloc(max_len + 4)) == NULL)
+    PFATAL("can not allocate %u memory", max_len + 4);
+  lenptr = (u32 *)buf;
+
+#ifdef USE_DEFLATE
+  buf2_len = (max_len > __afl_map_size ? max_len : __afl_map_size);
+  if ((buf2 = malloc(buf2_len + 8)) == NULL)
+    PFATAL("can not allocate %u memory", buf2_len + 8);
+  lenptr1 = (u32 *)buf2;
+  lenptr2 = (u32 *)(buf2 + 4);
+#endif
 
   memset(&hints, 0, sizeof(hints));
   hints.ai_socktype = SOCK_STREAM;
@@ -258,28 +276,81 @@ int main(int argc, char *argv[]) {
       fprintf(stderr,
               "Warning: binding to interface is not supported for your OS\n");
 #endif
+
+#ifdef SO_PRIORITY
+      int priority = 7;
+      if (setsockopt(s, SOL_SOCKET, SO_PRIORITY, &priority, sizeof(priority)) <
+          0) {
+
+        priority = 6;
+        if (setsockopt(s, SOL_SOCKET, SO_PRIORITY, &priority,
+                       sizeof(priority)) < 0)
+          WARNF("could not set priority on socket");
+
+      }
+
+#endif
+
       if (connect(s, aip->ai_addr, aip->ai_addrlen) == -1) s = -1;
 
     }
 
   }
 
+#ifdef USE_DEFLATE
+  struct libdeflate_compressor *compressor;
+  compressor = libdeflate_alloc_compressor(1);
+  struct libdeflate_decompressor *decompressor;
+  decompressor = libdeflate_alloc_decompressor();
+  fprintf(stderr, "Compile with compression support\n");
+#endif
+
   if (s == -1)
     FATAL("could not connect to target tcp://%s:%s", argv[1], argv[2]);
+  else
+    fprintf(stderr, "Connected to target tcp://%s:%s\n", argv[1], argv[2]);
 
   /* we initialize the shared memory map and start the forkserver */
   __afl_map_shm();
   __afl_start_forkserver();
 
-  int i = 1, j, status, ret;
+  int i = 1, j, status, ret, received;
+
   // fprintf(stderr, "Waiting for first testcase\n");
-  while ((len = __afl_next_testcase(buf, max_len)) > 0) {
+  while ((*lenptr = __afl_next_testcase(buf + 4, max_len)) > 0) {
+
+    // fprintf(stderr, "Sending testcase with len %u\n", *lenptr);
+#ifdef USE_DEFLATE
+    // we only compress the testcase if it does not fit in the TCP packet
+    if (*lenptr > 1500 - 20 - 32 - 4) {
+
+      // set highest byte to signify compression
+      *lenptr1 = (*lenptr | 0xff000000);
+      *lenptr2 = (u32)libdeflate_deflate_compress(compressor, buf + 4, *lenptr,
+                                                  buf2 + 8, buf2_len);
+      if (send(s, buf2, *lenptr2 + 8, 0) != *lenptr2 + 8)
+        PFATAL("sending test data failed");
+      fprintf(stderr, "COMPRESS (%u->%u):\n", *lenptr, *lenptr2);
+      for (u32 i = 0; i < *lenptr; i++)
+        fprintf(stderr, "%02x", buf[i + 4]);
+      fprintf(stderr, "\n");
+      for (u32 i = 0; i < *lenptr2; i++)
+        fprintf(stderr, "%02x", buf2[i + 8]);
+      fprintf(stderr, "\n");
+
+    } else {
 
-    // fprintf(stderr, "Sending testcase with len %u\n", len);
-    if (send(s, &len, 4, 0) != 4) PFATAL("sending size data %d failed", len);
-    if (send(s, buf, len, 0) != len) PFATAL("sending test data failed");
+#endif
+      if (send(s, buf, *lenptr + 4, 0) != *lenptr + 4)
+        PFATAL("sending test data failed");
+#ifdef USE_DEFLATE
+      // fprintf(stderr, "unCOMPRESS (%u)\n", *lenptr);
 
-    int received = 0;
+    }
+
+#endif
+
+    received = 0;
     while (received < 4 &&
            (ret = recv(s, &status + received, 4 - received, 0)) > 0)
       received += ret;
@@ -288,12 +359,37 @@ int main(int argc, char *argv[]) {
     // fprintf(stderr, "Received status\n");
 
     received = 0;
+#ifdef USE_DEFLATE
+    while (received < 4 &&
+           (ret = recv(s, &compress_len + received, 4 - received, 0)) > 0)
+      received += ret;
+    if (received != 4)
+      FATAL("did not receive compress_len (%d, %d)", received, ret);
+    // fprintf(stderr, "Received status\n");
+
+    received = 0;
+    while (received < compress_len &&
+           (ret = recv(s, buf2 + received, buf2_len - received, 0)) > 0)
+      received += ret;
+    if (received != compress_len)
+      FATAL("did not receive coverage data (%d, %d)", received, ret);
+
+    if (libdeflate_deflate_decompress(decompressor, buf2, compress_len,
+                                      __afl_area_ptr, __afl_map_size,
+                                      &decompress_len) != LIBDEFLATE_SUCCESS ||
+        decompress_len != __afl_map_size)
+      FATAL("decompression failed");
+// fprintf(stderr, "DECOMPRESS (%u->%u): ", compress_len, decompress_len);
+// for (u32 i = 0; i < __afl_map_size; i++) fprintf(stderr, "%02x",
+// __afl_area_ptr[i]); fprintf(stderr, "\n");
+#else
     while (received < __afl_map_size &&
            (ret = recv(s, __afl_area_ptr + received, __afl_map_size - received,
                        0)) > 0)
       received += ret;
     if (received != __afl_map_size)
       FATAL("did not receive coverage data (%d, %d)", received, ret);
+#endif
     // fprintf(stderr, "Received coverage\n");
 
     /* report the test case is done and wait for the next */
@@ -302,6 +398,11 @@ int main(int argc, char *argv[]) {
 
   }
 
+#ifdef USE_DEFLATE
+  libdeflate_free_compressor(compressor);
+  libdeflate_free_decompressor(decompressor);
+#endif
+
   return 0;
 
 }
diff --git a/examples/afl_network_proxy/afl-network-server.c b/examples/afl_network_proxy/afl-network-server.c
index e069af3d..e4c3bc6d 100644
--- a/examples/afl_network_proxy/afl-network-server.c
+++ b/examples/afl_network_proxy/afl-network-server.c
@@ -61,13 +61,21 @@
 #include <sys/socket.h>
 #include <netdb.h>
 
+#ifdef USE_DEFLATE
+#include <libdeflate.h>
+struct libdeflate_compressor *  compressor;
+struct libdeflate_decompressor *decompressor;
+#endif
+
 static u8 *in_file,                    /* Minimizer input test case         */
     *out_file;
 
 static u8 *in_data;                    /* Input data for trimming           */
+static u8 *buf2;
 
-static s32 in_len;
-static u32 map_size = MAP_SIZE;
+static s32    in_len;
+static u32    map_size = MAP_SIZE;
+static size_t buf2_len;
 
 static volatile u8 stop_soon;          /* Ctrl-C pressed?                   */
 
@@ -335,25 +343,64 @@ static void usage(u8 *argv0) {
 
 int recv_testcase(int s, void **buf, size_t *max_len) {
 
-  int size, received = 0, ret;
+  u32    size;
+  s32    ret;
+  size_t received;
 
+  received = 0;
   while (received < 4 && (ret = recv(s, &size + received, 4 - received, 0)) > 0)
     received += ret;
-
   if (received != 4) FATAL("did not receive size information");
-  if (size < 1) FATAL("did not receive valid size information");
+  if (size == 0) FATAL("did not receive valid size information");
   // fprintf(stderr, "received size information of %d\n", size);
 
-  *buf = maybe_grow(buf, max_len, size);
-  // fprintf(stderr, "receiving testcase %p %p max %u\n", buf, *buf, *max_len);
-  received = 0;
-  while (received < size &&
-         (ret = recv(s, ((char *)*buf) + received, size - received, 0)) > 0)
-    received += ret;
+  if ((size && 0xff000000) != 0xff000000) {
+
+    *buf = maybe_grow(buf, max_len, size);
+    received = 0;
+    // fprintf(stderr, "unCOMPRESS (%u)\n", size);
+    while (received < size &&
+           (ret = recv(s, ((char *)*buf) + received, size - received, 0)) > 0)
+      received += ret;
+
+  } else {
+
+#ifdef USE_DEFLATE
+    u32 clen;
+    size = (size & 0x00ffffff);
+    *buf = maybe_grow(buf, max_len, size);
+    received = 0;
+    while (received < 4 &&
+           (ret = recv(s, &clen + received, 4 - received, 0)) > 0)
+      received += ret;
+    if (received != 4) FATAL("did not receive size information");
+    // fprintf(stderr, "received clen information of %d\n", clen);
+    if (clen < 1)
+      FATAL("did not receive valid compressed len information: %u", clen);
+    buf2 = maybe_grow((void **)&buf2, &buf2_len, clen);
+    received = 0;
+    while (received < clen &&
+           (ret = recv(s, buf2 + received, clen - received, 0)) > 0)
+      received += ret;
+    if (received != clen) FATAL("did not receive compressed information");
+    if (libdeflate_deflate_decompress(decompressor, buf2, clen, (char *)*buf,
+                                      *max_len,
+                                      &received) != LIBDEFLATE_SUCCESS)
+      FATAL("decompression failed");
+      // fprintf(stderr, "DECOMPRESS (%u->%u):\n", clen, received);
+      // for (u32 i = 0; i < clen; i++) fprintf(stderr, "%02x", buf2[i]);
+      // fprintf(stderr, "\n");
+      // for (u32 i = 0; i < received; i++) fprintf(stderr, "%02x",
+      // ((u8*)(*buf))[i]); fprintf(stderr, "\n");
+#else
+    FATAL("Received compressed data but not compiled with compression support");
+#endif
+
+  }
 
+  // fprintf(stderr, "receiving testcase %p %p max %u\n", buf, *buf, *max_len);
   if (received != size)
     FATAL("did not receive testcase data %u != %u, %d", received, size, ret);
-
   // fprintf(stderr, "received testcase\n");
   return size;
 
@@ -371,6 +418,10 @@ int main(int argc, char **argv_orig, char **envp) {
   int                 addrlen = sizeof(clientaddr);
   char                str[INET6_ADDRSTRLEN];
   char **             argv = argv_cpy_dup(argc, argv_orig);
+  u8 *                send_buf;
+#ifdef USE_DEFLATE
+  u32 *lenptr;
+#endif
 
   afl_forkserver_t  fsrv_var = {0};
   afl_forkserver_t *fsrv = &fsrv_var;
@@ -378,6 +429,8 @@ int main(int argc, char **argv_orig, char **envp) {
   map_size = get_map_size();
   fsrv->map_size = map_size;
 
+  if ((send_buf = malloc(map_size + 4)) == NULL) PFATAL("malloc");
+
   while ((opt = getopt(argc, argv, "+i:f:m:t:QUWh")) > 0) {
 
     switch (opt) {
@@ -553,6 +606,21 @@ int main(int argc, char **argv_orig, char **envp) {
   }
 
 #endif
+
+#ifdef SO_PRIORITY
+  int priority = 7;
+  if (setsockopt(sock, SOL_SOCKET, SO_PRIORITY, &priority, sizeof(priority)) <
+      0) {
+
+    priority = 6;
+    if (setsockopt(sock, SOL_SOCKET, SO_PRIORITY, &priority, sizeof(priority)) <
+        0)
+      WARNF("could not set priority on socket");
+
+  }
+
+#endif
+
   memset(&serveraddr, 0, sizeof(serveraddr));
   serveraddr.sin6_family = AF_INET6;
   serveraddr.sin6_port = htons(port);
@@ -566,6 +634,14 @@ int main(int argc, char **argv_orig, char **envp) {
   afl_fsrv_start(fsrv, use_argv, &stop_soon,
                  get_afl_env("AFL_DEBUG_CHILD_OUTPUT") ? 1 : 0);
 
+#ifdef USE_DEFLATE
+  compressor = libdeflate_alloc_compressor(1);
+  decompressor = libdeflate_alloc_decompressor();
+  buf2 = maybe_grow((void **)&buf2, &buf2_len, map_size + 16);
+  lenptr = (u32 *)(buf2 + 4);
+  fprintf(stderr, "Compiled with compression support\n");
+#endif
+
   fprintf(stderr,
           "Waiting for incoming connection from afl-network-client on port %d "
           "...\n",
@@ -574,15 +650,40 @@ int main(int argc, char **argv_orig, char **envp) {
   if ((s = accept(sock, NULL, NULL)) < 0) { PFATAL("accept() failed"); }
   fprintf(stderr, "Received connection, starting ...\n");
 
+#ifdef SO_PRIORITY
+  priority = 7;
+  if (setsockopt(s, SOL_SOCKET, SO_PRIORITY, &priority, sizeof(priority)) < 0) {
+
+    priority = 6;
+    if (setsockopt(s, SOL_SOCKET, SO_PRIORITY, &priority, sizeof(priority)) < 0)
+      WARNF("could not set priority on socket");
+
+  }
+
+#endif
+
   while ((in_len = recv_testcase(s, (void **)&in_data, &max_len)) > 0) {
 
     // fprintf(stderr, "received %u\n", in_len);
     run_target(fsrv, use_argv, in_data, in_len, 1);
 
-    if (send(s, &fsrv->child_status, 4, 0) != 4)
-      FATAL("could not send waitpid data");
-    if (send(s, fsrv->trace_bits, fsrv->map_size, 0) != fsrv->map_size)
-      FATAL("could not send coverage data");
+    memcpy(send_buf + 4, fsrv->trace_bits, fsrv->map_size);
+
+#ifdef USE_DEFLATE
+    memcpy(buf2, &fsrv->child_status, 4);
+    *lenptr = (u32)libdeflate_deflate_compress(
+        compressor, send_buf + 4, fsrv->map_size, buf2 + 8, buf2_len - 8);
+    // fprintf(stderr, "COMPRESS (%u->%u): ", fsrv->map_size, *lenptr);
+    // for (u32 i = 0; i < fsrv->map_size; i++) fprintf(stderr, "%02x",
+    // fsrv->trace_bits[i]); fprintf(stderr, "\n");
+    if (send(s, buf2, *lenptr + 8, 0) != 8 + *lenptr)
+      FATAL("could not send data");
+#else
+    memcpy(send_buf, &fsrv->child_status, 4);
+    if (send(s, send_buf, fsrv->map_size + 4, 0) != 4 + fsrv->map_size)
+      FATAL("could not send data");
+#endif
+
     // fprintf(stderr, "sent result\n");
 
   }
@@ -595,6 +696,11 @@ int main(int argc, char **argv_orig, char **envp) {
   afl_fsrv_deinit(fsrv);
   if (fsrv->target_path) { ck_free(fsrv->target_path); }
   if (in_data) { ck_free(in_data); }
+#if USE_DEFLATE
+  if (buf2) { ck_free(buf2); }
+  libdeflate_free_compressor(compressor);
+  libdeflate_free_decompressor(decompressor);
+#endif
 
   argv_cpy_free(argv);
 
-- 
cgit 1.4.1


From 945e00b73fde56f98235a03472b4af1539983f80 Mon Sep 17 00:00:00 2001
From: van Hauser <vh@thc.org>
Date: Mon, 4 May 2020 12:51:38 +0200
Subject: final touches for afl_network_proxy

---
 examples/afl_network_proxy/GNUmakefile | 24 ++++++++----------------
 examples/afl_network_proxy/README.md   | 11 +++++++----
 2 files changed, 15 insertions(+), 20 deletions(-)

(limited to 'examples/afl_network_proxy/README.md')

diff --git a/examples/afl_network_proxy/GNUmakefile b/examples/afl_network_proxy/GNUmakefile
index 93eee4c1..99221d10 100644
--- a/examples/afl_network_proxy/GNUmakefile
+++ b/examples/afl_network_proxy/GNUmakefile
@@ -10,27 +10,19 @@ ifdef STATIC
   CFLAGS += -static
 endif
 
-ifdef USE_DEFLATE
-  CFLAGS += -DUSE_DEFLATE=1
-  LDFLAGS += -ldeflate
-  $(info activating libdeflate-dev for compressing)
+ifeq "$(shell echo '$(HASH)include <libdeflate.h>@int main() { struct libdeflate_compressor *d = libdeflate_alloc_compressor(1); return 0;}' | tr @ '\n' | $(CC) $(CFLAGS) -x c - -o .test2 -ldeflate 2>/dev/null && echo 1 || echo 0 ; rm -f .test2 )" "1"
+ CFLAGS += -ldeflate -DUSE_DEFLATE=1
+ $(info libdeflate-dev was detected, using compressing)
+else
+ $(warn did not find libdeflate-dev, cannot use compression)
 endif
 
-# Disables because compression is slower
-# sending 64kb instead of compressing to 112bytes is slower? weird ...
-#ifeq "$(shell echo '$(HASH)include <libdeflate.h>@int main() { struct libdeflate_compressor *d = libdeflate_alloc_compressor(1); return 0;}' | tr @ '\n' | $(CC) $(CFLAGS) -x c - -o .test2 -ldeflate 2>/dev/null && echo 1 || echo 0 ; rm -f .test2 )" "1"
-# CFLAGS += -ldeflate -DUSE_DEFLATE=1
-# $(info libdeflate-dev was detected, using compressing)
-#else
-# $(warn did not find libdeflate-dev, cannot use compression)
-#endif
-
 all:	$(PROGRAMS)
 
 help:
 	@echo make options:
-	echo STATIC - build as static binaries
-	echo USE_DEFLATE - build with compression library
+	@echo STATIC - build as static binaries
+	@echo COMPRESS_TESTCASES - compress test cases
 
 afl-network-client:	afl-network-client.c
 	$(CC) $(CFLAGS) -I../../include -o afl-network-client afl-network-client.c $(LDFLAGS)
@@ -44,5 +36,5 @@ clean:
 install: all
 	install -d -m 755 $${DESTDIR}$(BIN_PATH) $${DESTDIR}$(DOC_PATH)
 	install -m 755 $(PROGRAMS) $${DESTDIR}$(BIN_PATH)
-	install -m 644 README.md $${DESTDIR}$(DOC_PATH)/README.network_proxy.md
+	install -T -m 644 README.md $${DESTDIR}$(DOC_PATH)/README.network_proxy.md
 
diff --git a/examples/afl_network_proxy/README.md b/examples/afl_network_proxy/README.md
index 84ebfa48..255be0d8 100644
--- a/examples/afl_network_proxy/README.md
+++ b/examples/afl_network_proxy/README.md
@@ -16,9 +16,12 @@ Note that the impact on fuzzing speed will be huge, expect a loss of 90%.
 
 Just type `make` and let the autodetection do everything for you.
 
-Note that compression is supported but currently disabled. It seems that
-sending 64kb of map data over TCP is faster than compressing it with the
-fastest algorithm and options to 112 byte and sending this. Weird.
+Note that you will get a 40-50% performance increase if you have libdeflate-dev
+installed. The GNUmakefile will autodetect it if present.
+
+If your target has large test cases (10+kb) that are ascii only or large chunks
+of zero blocks then set `CFLAGS=-DCOMPRESS_TESTCASES=1` to compress them.
+For most targets this hurts performance though so it is disabled by default.
 
 ### on the target
 
@@ -29,7 +32,7 @@ e.g.:
 $ afl-network-server -i 1111 -m 25M -t 1000 -- /bin/target -f @@
 ```
 
-### on the fuzzing master
+### on the (afl-fuzz) master
 
 Just run afl-fuzz with your normal options, however the target should be
 `afl-network-client` with the IP and PORT of the `afl-network-server` and
-- 
cgit 1.4.1


From dc795331910bb0f0b31a3eb66ccb71432d0a4e22 Mon Sep 17 00:00:00 2001
From: van Hauser <vh@thc.org>
Date: Tue, 5 May 2020 20:29:40 +0200
Subject: more typos fixed

---
 examples/afl_network_proxy/README.md | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

(limited to 'examples/afl_network_proxy/README.md')

diff --git a/examples/afl_network_proxy/README.md b/examples/afl_network_proxy/README.md
index 255be0d8..42c0b71b 100644
--- a/examples/afl_network_proxy/README.md
+++ b/examples/afl_network_proxy/README.md
@@ -26,7 +26,7 @@ For most targets this hurts performance though so it is disabled by default.
 ### on the target
 
 Run `afl-network-server` with your target with the -m and -t values you need.
-Important is the -i parameter which is the TCP port to liste on.
+Important is the -i parameter which is the TCP port to listen on.
 e.g.:
 ```
 $ afl-network-server -i 1111 -m 25M -t 1000 -- /bin/target -f @@
@@ -40,9 +40,9 @@ increase the -t value:
 ```
 $ afl-fuzz -i in -o out -t 2000+ -- afl-network-client TARGET-IP 1111
 ```
-Note the '+' on the -t parameter value. the afl-network-server will take
-care of proper timeouts hence afl-fuzz should not. The '+' increases the timout
-and the value itself should be 500-1000 higher than the one on 
+Note the '+' on the -t parameter value. The afl-network-server will take
+care of proper timeouts hence afl-fuzz should not. The '+' increases the
+timeout and the value itself should be 500-1000 higher than the one on 
 afl-network-server.
 
 ### networking
@@ -51,9 +51,9 @@ The TARGET can be an IPv4 or IPv6 address, or a host name that resolves to
 either. Note that also the outgoing interface can be specified with a '%' for
 `afl-network-client`, e.g. `fe80::1234%eth0`.
 
-Also make sure your middle value of `/proc/sys/net/ipv4/tcp_rmem` is larger
-than your MAP_SIZE (130kb is a good value). This is the default TCP window
-size value.
+Also make sure your default TCP window size is larger than your MAP_SIZE
+(130kb is a good value).
+On Linux that is the middle value of `/proc/sys/net/ipv4/tcp_rmem` 
 
 ## how to compile and install
 
-- 
cgit 1.4.1