- Add option to change zlib windowBits/memLevel

2 files changed, 24 insertions, 1 deletions

diff --git a/common-kex.c b/common-kex.c
index 052324b..cb5cd96 100644
--- a/common-kex.c
+++ b/common-kex.c
@@ -371,7 +371,9 @@ static void gen_new_zstreams() {
 		ses.newkeys->trans.zstream->zalloc = Z_NULL;
 		ses.newkeys->trans.zstream->zfree = Z_NULL;
 	
-		if (deflateInit(ses.newkeys->trans.zstream, Z_DEFAULT_COMPRESSION) 
+		if (deflateInit2(ses.newkeys->trans.zstream, Z_DEFAULT_COMPRESSION,
+					Z_DEFLATED, DROPBEAR_ZLIB_WINDOW_BITS, 
+					DROPBEAR_ZLIB_MEM_LEVEL, Z_DEFAULT_STRATEGY)
 				!= Z_OK) {
 			dropbear_exit("zlib error");
 		}
diff --git a/options.h b/options.h
index 2d6f7b6..3cf430b 100644
--- a/options.h
+++ b/options.h
@@ -130,6 +130,21 @@ much traffic. */
  * if the random number source isn't good. In general this isn't required */
 /* #define DSS_PROTOK */
 
+/* Control the memory/performance/compression tradeoff for zlib.
+ * Set windowBits=8, memLevel=1 for least memory usage, see your system's
+ * zlib.h for full details.
+ * Default settings (windowBits=15, memLevel=8) will use 
+ * 256kB for compression + 32kB for decompression.
+ * windowBits=8, memLevel=1 will use 10kB compression + 32kB decompression.
+ * Note that windowBits is only set for deflate() - inflate() always uses the
+ * default of 15 so as to interoperate with other clients. */
+#ifndef DROPBEAR_ZLIB_WINDOW_BITS
+#define DROPBEAR_ZLIB_WINDOW_BITS 15 
+#endif
+#ifndef DROPBEAR_ZLIB_MEM_LEVEL
+#define DROPBEAR_ZLIB_MEM_LEVEL 8
+#endif
+
 /* Whether to do reverse DNS lookups. */
 #define DO_HOST_LOOKUP
 
@@ -248,13 +263,19 @@ much traffic. */
    significant difference to network performance. 24kB was empirically
    chosen for a 100mbit ethernet network. The value can be altered at
    runtime with the -W argument. */
+#ifndef DEFAULT_RECV_WINDOW
 #define DEFAULT_RECV_WINDOW 24576
+#endif
 /* Maximum size of a received SSH data packet - this _MUST_ be >= 32768
    in order to interoperate with other implementations */
+#ifndef RECV_MAX_PAYLOAD_LEN
 #define RECV_MAX_PAYLOAD_LEN 32768
+#endif
 /* Maximum size of a transmitted data packet - this can be any value,
    though increasing it may not make a significant difference. */
+#ifndef TRANS_MAX_PAYLOAD_LEN
 #define TRANS_MAX_PAYLOAD_LEN 16384
+#endif
 
 /* Ensure that data is transmitted every KEEPALIVE seconds. This can
 be overridden at runtime with -K. 0 disables keepalives */