On 6/30/20 12:56 AM, Tuong Lien wrote:
In commit 16ad3f4022bb ("tipc: introduce variable window congestion
control"), we enable user to set the link 'max_win' value which is used
as the upper threshold for the variable link window algorithm later.
However, since it is done by the same netlink command property
'TIPC_NLA_PROP_WIN' that was used to set the actual link window before,
it appears to be a non backward compatible issue when user tries to get
the value back but finds a different value (i.e. the variable window at
that moment).
Besides, there is another flaw with the 'max_win' where it is set to be
'TIPC_MAX_LINK_WIN' (i.e. 8191) by default that is obviously unexpected
(the variable link window will take place and go beyond that might harm
the underlying device...). The value is actually derived from the lower
bearer & media layers (i.e. 'eth' media) at the initializing time where
the default value should be 'TIPC_DEF_LINK_WIN' (i.e. 50) instead.
We fix the issue #1 by returning the 'max_win' which is exactly the one
set by user, while setting back the 'max_win' for the 'eth' media to be
the said value for the #2.
Note: the changes do not affect the variable link window mechanism, but
make the right thing i.e. it will work only when user really wants.
If understand this right variable window flow control will now in
practice be disabled by default, and only be activated if the user
explicitly sets max_win to something >> 50. Right?
///jon
Fixes: 16ad3f4022bb ("tipc: introduce variable window congestion control")
Reported-by: Hoang Le <hoang.h...@dektech.com.au>
Reported-by: Thang Ngo <thang.h....@dektech.com.au>
Signed-off-by: Tuong Lien <tuong.t.l...@dektech.com.au>
---
net/tipc/eth_media.c | 2 +-
net/tipc/link.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/net/tipc/eth_media.c b/net/tipc/eth_media.c
index 8b0bb600602d..675b947eab89 100644
--- a/net/tipc/eth_media.c
+++ b/net/tipc/eth_media.c
@@ -93,7 +93,7 @@ struct tipc_media eth_media_info = {
.priority = TIPC_DEF_LINK_PRI,
.tolerance = TIPC_DEF_LINK_TOL,
.min_win = TIPC_DEF_LINK_WIN,
- .max_win = TIPC_MAX_LINK_WIN,
+ .max_win = TIPC_DEF_LINK_WIN,
.type_id = TIPC_MEDIA_TYPE_ETH,
.hwaddr_len = ETH_ALEN,
.name = "eth"
diff --git a/net/tipc/link.c b/net/tipc/link.c
index ee3b8d0576b8..28834dafdc98 100644
--- a/net/tipc/link.c
+++ b/net/tipc/link.c
@@ -2662,7 +2662,7 @@ int __tipc_nl_add_link(struct net *net, struct
tipc_nl_msg *msg,
if (nla_put_u32(msg->skb, TIPC_NLA_PROP_TOL, link->tolerance))
goto prop_msg_full;
if (nla_put_u32(msg->skb, TIPC_NLA_PROP_WIN,
- link->window))
+ link->max_win))
goto prop_msg_full;
if (nla_put_u32(msg->skb, TIPC_NLA_PROP_PRIO, link->priority))
goto prop_msg_full;
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