MINOR: compression: Enable compression for IE6 w/SP2, IE7 and IE8
Some old browsers that have a user-agent starting with "Mozilla/4" do
not support compressison correctly, so disable compression for those.
Internet explorer 6 after Windows XP service pack 2, IE 7, and IE 8,
do however support compression and still have a user agent starting
with Mozilla/4, so we try to enable compression for those.
MSIE has a user-agent on this form:
Mozilla/4.0 (compatible; MSIE <version>; ...)
98% of MSIE 6 SP2 user agents start with
Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1
The remaining 2% have additional flags before "SV1".
This simplified matching looking for MSIE at exactly position 25
and SV1 at exacly position 51 gives a few false negatives, so sometimes
a compression opportunity is lost.
A test against 3 hours of traffic to around 3000 news sites worldwide
gives less than 0.007% (70ppm) missed compression opportunities.
diff --git a/src/proto_http.c b/src/proto_http.c
index 61730d7..cb24eb0 100644
--- a/src/proto_http.c
+++ b/src/proto_http.c
@@ -1974,16 +1974,21 @@
struct comp_algo *comp_algo = NULL;
struct comp_algo *comp_algo_back = NULL;
- /* Disable compression for older user agents announcing themselves as "Mozilla/4".
- * Note all of them are broken but they are very few and the broken ones are there.
+ /* Disable compression for older user agents announcing themselves as "Mozilla/4"
+ * unless they are known good (MSIE 6 with XP SP2, or MSIE 7 and later).
* See http://zoompf.com/2012/02/lose-the-wait-http-compression for more details.
*/
ctx.idx = 0;
if (http_find_header2("User-Agent", 10, req->p, &txn->hdr_idx, &ctx) &&
ctx.vlen >= 9 &&
- memcmp(ctx.line + ctx.val, "Mozilla/4", 9) == 0) {
- s->comp_algo = NULL;
- return 0;
+ memcmp(ctx.line + ctx.val, "Mozilla/4", 9) == 0 &&
+ (ctx.vlen < 31 ||
+ memcmp(ctx.line + ctx.val + 25, "MSIE ", 5) != 0 ||
+ ctx.line[ctx.val + 30] < '6' ||
+ (ctx.line[ctx.val + 30] == '6' &&
+ (ctx.vlen < 54 || memcmp(ctx.line + 51, "SV1", 3) != 0)))) {
+ s->comp_algo = NULL;
+ return 0;
}
ctx.idx = 0;