Am 14.12.21 um 18:10 schrieb Frank Lichtenheld:
Arne Schwabe <a...@rfc2549.org> hat am 14.12.2021 16:09 geschrieben:
This consolidates the MSS fix calculation into a single function
instead having it distributed all over the code. It also calculates
the real wire overhead without extra sizes for buffer etc.
Patch v2: improve comment
Signed-off-by: Arne Schwabe <a...@rfc2549.org>
---
src/openvpn/forward.c | 5 ++---
src/openvpn/init.c | 3 ++-
src/openvpn/mss.c | 40 ++++++++++++++++++++++++++++++++++++++++
src/openvpn/mss.h | 6 ++++++
src/openvpn/mtu.c | 9 ---------
src/openvpn/mtu.h | 10 ++++++----
src/openvpn/proto.h | 11 -----------
src/openvpn/ssl.c | 3 ++-
8 files changed, 58 insertions(+), 29 deletions(-)
diff --git a/src/openvpn/forward.c b/src/openvpn/forward.c
index 29efcd3b9..f82386a1d 100644
--- a/src/openvpn/forward.c
+++ b/src/openvpn/forward.c
@@ -1493,7 +1493,7 @@ process_ip_header(struct context *c, unsigned int flags,
struct buffer *buf)
/* possibly alter the TCP MSS */
if (flags & PIP_MSSFIX)
{
- mss_fixup_ipv4(&ipbuf,
MTU_TO_MSS(TUN_MTU_SIZE_DYNAMIC(&c->c2.frame)));
+ mss_fixup_ipv4(&ipbuf, c->c2.frame.mss_fix);
I still think this will badly explode in the ce.mssfix == 0 code path. In that
case frame.mss_fix == 0 AFAICT
and I see no handling of that possibility in mss_fixup_ipv4/6.
I won't. This is part of the older parts of OpenVPN that are more
obscure. You overlooking the implicit assumption that PIP_MSSFIX is only
set if also c->c2.frame.mssfix is != 0
See the top of the function. If ce.mssfix is 0 then you never have the
PIP_MSSFIX flag in the flags:
void
process_ip_header(struct context *c, unsigned int flags, struct buffer *buf)
{
if (!c->options.ce.mssfix)
{
flags &= ~PIP_MSSFIX;
}
Arne
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