I have an easier patch in my private repo, maybe it's enough without a
new configuration option? I'm using it in production for a gretap link
which is bridged on both sides to MTU 1500 ethernet links.
See https://bugzilla.kernel.org/show_bug.cgi?id=14837, which seems to
say you always have to use both options: ignore-df nopmtudisc
Signed-off-by: Stefan Hellermann <ste...@the2masters.de>
--- a/system-linux.c
+++ b/system-linux.c
@@ -3496,6 +3496,7 @@ static int system_add_gre_tunnel(const c
ttl = 64;
nla_put_u8(nlm, IFLA_GRE_PMTUDISC, set_df ? 1 : 0);
+ nla_put_u8(nlm, IFLA_GRE_IGNORE_DF, set_df ? 0 : 1);
nla_put_u8(nlm, IFLA_GRE_TOS, tos);
}
Am 17.04.23 um 11:29 schrieb Denis Kalashnikov:
This is useful for GRE TAP tunnel when tunnel is added to a br-lan bridge.
In this case you need to create it with "nopmtudisc ignore-df". Otherwise
large IP-packets with DF=1 (TCP-data, large pings) will be silently dropped
(since DF=1 but stack failed to send ICMP "need fragmentation" back). But with
"ignore-df" packets with DF=1 will be fragmented.
Signed-off-by: Denis Kalashnikov <denis281...@gmail.com>
---
system-linux.c | 5 +++++
system.c | 1 +
system.h | 1 +
3 files changed, 7 insertions(+)
diff --git a/system-linux.c b/system-linux.c
index e4041fb..4397460 100644
--- a/system-linux.c
+++ b/system-linux.c
@@ -3500,6 +3500,11 @@ static int system_add_gre_tunnel(const char *name, const
char *kind,
nla_put_u8(nlm, IFLA_GRE_PMTUDISC, set_df ? 1 : 0);
+ if ((cur = tb[TUNNEL_ATTR_IGNORE_DF])) {
+ nla_put_u8(nlm, IFLA_GRE_IGNORE_DF,
+ blobmsg_get_bool(cur));
+ }
+
nla_put_u8(nlm, IFLA_GRE_TOS, tos);
}
diff --git a/system.c b/system.c
index 32597c1..e773245 100644
--- a/system.c
+++ b/system.c
@@ -21,6 +21,7 @@ static const struct blobmsg_policy
tunnel_attrs[__TUNNEL_ATTR_MAX] = {
[TUNNEL_ATTR_REMOTE] = { .name = "remote", .type = BLOBMSG_TYPE_STRING
},
[TUNNEL_ATTR_MTU] = { .name = "mtu", .type = BLOBMSG_TYPE_INT32 },
[TUNNEL_ATTR_DF] = { .name = "df", .type = BLOBMSG_TYPE_BOOL },
+ [TUNNEL_ATTR_IGNORE_DF] = { .name = "ignore-df", .type =
BLOBMSG_TYPE_BOOL },
[TUNNEL_ATTR_TTL] = { .name = "ttl", .type = BLOBMSG_TYPE_INT32 },
[TUNNEL_ATTR_TOS] = { .name = "tos", .type = BLOBMSG_TYPE_STRING },
[TUNNEL_ATTR_LINK] = { .name = "link", .type = BLOBMSG_TYPE_STRING },
diff --git a/system.h b/system.h
index 1f7037d..a7a713d 100644
--- a/system.h
+++ b/system.h
@@ -29,6 +29,7 @@ enum tunnel_param {
TUNNEL_ATTR_LOCAL,
TUNNEL_ATTR_MTU,
TUNNEL_ATTR_DF,
+ TUNNEL_ATTR_IGNORE_DF,
TUNNEL_ATTR_TTL,
TUNNEL_ATTR_TOS,
TUNNEL_ATTR_LINK,
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