[PATCH] net: sctp: bug-fixing: retran_path not set properly after transports recovering (v2)

[PATCH] net: sctp: bug-fixing: retran_path not set properly after transports recovering (v2)

[Chang Xiangzhong]

When a transport recovers due to the new coming sack, SCTP should
iterate all of its transport_list to locate the __two__ most recently used
transport and set to active_path and retran_path respectively. The exising
code does not find the two properly - In case of the following list:

[most-recent] -> [2nd-most-recent] -> ...

Both active_path and retran_path would be set to the 1st element.

The bug happens when:
1) multi-homing
2) failure/partial_failure transport recovers
Both active_path and retran_path would be set to the same most-recent one, in
other words, retran_path would not take its role - an end user might not even
notice this issue.

Signed-off-by: Chang Xiangzhong <changxiangzhong@gmail.com>
---
 net/sctp/associola.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/sctp/associola.c b/net/sctp/associola.c
index ab67efc..a7fc856 100644
--- a/net/sctp/associola.c
+++ b/net/sctp/associola.c
@@ -913,11 +913,12 @@ void sctp_assoc_control_transport(struct sctp_association *asoc,
 		if (!first || t->last_time_heard > first->last_time_heard) {
 			second = first;
 			first = t;
-		}
-		if (!second || t->last_time_heard > second->last_time_heard)
+		} else if (!second ||
+				t->last_time_heard > second->last_time_heard)
 			second = t;
 	}
 
+
 	/* RFC 2960 6.4 Multi-Homed SCTP Endpoints
 	 *
 	 * By default, an endpoint should always transmit to the
@@ -935,6 +936,8 @@ void sctp_assoc_control_transport(struct sctp_association *asoc,
 		first = asoc->peer.primary_path;
 	}
 
+	if (!second)
+		second = first;
 	/* If we failed to find a usable transport, just camp on the
 	 * primary, even if it is inactive.
 	 */
-- 
1.7.9.5

Re: [PATCH] net: sctp: bug-fixing: retran_path not set properly after transports recovering (v2)

[Vlad Yasevich]

On 11/13/2013 04:54 PM, Chang Xiangzhong wrote:
> When a transport recovers due to the new coming sack, SCTP should
> iterate all of its transport_list to locate the __two__ most recently used
> transport and set to active_path and retran_path respectively. The exising
> code does not find the two properly - In case of the following list:
>
> [most-recent] -> [2nd-most-recent] -> ...
>
> Both active_path and retran_path would be set to the 1st element.
>
> The bug happens when:
> 1) multi-homing
> 2) failure/partial_failure transport recovers
> Both active_path and retran_path would be set to the same most-recent one, in
> other words, retran_path would not take its role - an end user might not even
> notice this issue.
>
> Signed-off-by: Chang Xiangzhong <changxiangzhong@gmail.com>
> ---
>   net/sctp/associola.c |    7 +++++--
>   1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/net/sctp/associola.c b/net/sctp/associola.c
> index ab67efc..a7fc856 100644
> --- a/net/sctp/associola.c
> +++ b/net/sctp/associola.c
> @@ -913,11 +913,12 @@ void sctp_assoc_control_transport(struct sctp_association *asoc,
>   		if (!first || t->last_time_heard > first->last_time_heard) {
>   			second = first;
>   			first = t;
> -		}
> -		if (!second || t->last_time_heard > second->last_time_heard)
> +		} else if (!second ||
> +				t->last_time_heard > second->last_time_heard)

Align with !second.

>   			second = t;
>   	}
>
> +

Spurious new line.

-vlad
>   	/* RFC 2960 6.4 Multi-Homed SCTP Endpoints
>   	 *
>   	 * By default, an endpoint should always transmit to the
> @@ -935,6 +936,8 @@ void sctp_assoc_control_transport(struct sctp_association *asoc,
>   		first = asoc->peer.primary_path;
>   	}
>
> +	if (!second)
> +		second = first;
>   	/* If we failed to find a usable transport, just camp on the
>   	 * primary, even if it is inactive.
>   	 */
>