src/patches/dhcpcd-10.0.2-Allow-free-selection-of-MTU-by-the-user.patch

   1 From 1acff721a3874a74efc9921a1e07bd48bd7efab0 Mon Sep 17 00:00:00 2001
   2 From: Michael Tremer <michael.tremer@ipfire.org>
   3 Date: Tue, 22 Feb 2022 12:07:15 +0000
   4 Subject: [PATCH] Allow free selection of MTU by the user
   5
   6 Various ISPs (or equipment?) seem to hand out an MTU of only 576 bytes.
   7 Hwoever, this does not seem to be intentional which is why we would like
   8 to manually overwrite this in the configuration.
   9
  10 dhcpcd only allows setting a maximum MTU of 1472 bytes which does not
  11 seem to have any rationale (any more). Although Ethernet might limit any
  12 MTU to less, IPv6 and IPv4 support MTUs of up to 64KiB.
  13
  14 This patch allows the user to configure the MTU freely with providing
  15 some sanity check.
  16
  17 Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>
  18 ---
  19  src/dhcp-common.h | 9 +++++----
  20  1 file changed, 5 insertions(+), 4 deletions(-)
  21
  22 diff --git a/src/dhcp-common.h b/src/dhcp-common.h
  23 index a82fcd4c..d6620822 100644
  24 --- a/src/dhcp-common.h
  25 +++ b/src/dhcp-common.h
  26 @@ -46,10 +46,11 @@
  27  #define NS_MAXLABEL MAXLABEL
  28  #endif
  29
  30 -/* Max MTU - defines dhcp option length */
  31 -#define        IP_UDP_SIZE               28
  32 -#define        MTU_MAX                 1500 - IP_UDP_SIZE
  33 -#define        MTU_MIN                  576 + IP_UDP_SIZE
  34 +/* Max/Min MTU */
  35 +#define        MTU_MAX                 65536
  36 +#define        MTU_MIN                   576
  37 +
  38 +#define        IP_UDP_SIZE                28
  39
  40  #define        OT_REQUEST              (1 << 0)
  41  #define        OT_UINT8                (1 << 1)
  42 --
  43 2.30.2
  44