From: Philippe Antoine <pantoine@oisf.net>
Date: Wed, 31 May 2023 12:53:28 +0000 (+0200)
Subject: http2: avoid quadratic complexity in headers
X-Git-Tag: suricata-7.0.0-rc2~83
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=635073688289aa9a4928f78cdfd1777ae21f7d40;p=thirdparty%2Fsuricata.git

http2: avoid quadratic complexity in headers

When adding an element to the dynamic headers table, the oldest
ones may get evicted. When multiple elements get evicted, they
should get evicted all at once with drain, instead of one by one
as there will be a massive move each time.

Ticket: #6103
---

diff --git a/rust/src/http2/parser.rs b/rust/src/http2/parser.rs
index 88486f03b0..adabeb28c6 100644
--- a/rust/src/http2/parser.rs
+++ b/rust/src/http2/parser.rs
@@ -456,13 +456,15 @@ fn http2_parse_headers_block_literal_incindex<'a>(
                 } else {
                     dyn_headers.table.push(headcopy);
                 }
+                let mut toremove = 0;
                 while dyn_headers.current_size > dyn_headers.max_size
-                    && !dyn_headers.table.is_empty()
+                    && toremove < dyn_headers.table.len()
                 {
                     dyn_headers.current_size -=
-                        32 + dyn_headers.table[0].name.len() + dyn_headers.table[0].value.len();
-                    dyn_headers.table.remove(0);
+                        32 + dyn_headers.table[toremove].name.len() + dyn_headers.table[toremove].value.len();
+                    toremove += 1;
                 }
+                dyn_headers.table.drain(0..toremove);
             }
             return Ok((r, head));
         }