netdev - [PATCH v2 2/3] sctp_diag: export timer value only if it is active

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Message-Id: <1470259393-22861-3-git-send-email-phil@nwl.cc>
Date:	Wed,  3 Aug 2016 23:23:12 +0200
From:	Phil Sutter <phil@....cc>
To:	David Miller <davem@...emloft.net>
Cc:	Xin Long <lucien.xin@...il.com>,
	Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
	netdev@...r.kernel.org
Subject: [PATCH v2 2/3] sctp_diag: export timer value only if it is active

Since it is exported as unsigned value, userspace has no way detecting
whether it is negative or just very large. Therefore do this in kernel
space where it is a simple comparison.

Signed-off-by: Phil Sutter <phil@....cc>
---
Changes since v1:
- Introduce local variable to shorten long lines.
- Use timer_pending() to decide whether to export the timer value.
- Export the primary path's value instead of garbage.
- If not exporting, zero fields to not confuse userspace.
---
 net/sctp/sctp_diag.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/net/sctp/sctp_diag.c b/net/sctp/sctp_diag.c
index f69edcf219e51..f728ef04a7b2d 100644
--- a/net/sctp/sctp_diag.c
+++ b/net/sctp/sctp_diag.c
@@ -13,6 +13,7 @@ static void inet_diag_msg_sctpasoc_fill(struct inet_diag_msg *r,
 {
 	union sctp_addr laddr, paddr;
 	struct dst_entry *dst;
+	struct timer_list *t3_rtx = &asoc->peer.primary_path->T3_rtx_timer;
 
 	laddr = list_entry(asoc->base.bind_addr.address_list.next,
 			   struct sctp_sockaddr_entry, list)->a;
@@ -40,10 +41,15 @@ static void inet_diag_msg_sctpasoc_fill(struct inet_diag_msg *r,
 	}
 
 	r->idiag_state = asoc->state;
-	r->idiag_timer = SCTP_EVENT_TIMEOUT_T3_RTX;
-	r->idiag_retrans = asoc->rtx_data_chunks;
-	r->idiag_expires = jiffies_to_msecs(
-		asoc->timeouts[SCTP_EVENT_TIMEOUT_T3_RTX] - jiffies);
+	if (timer_pending(t3_rtx)) {
+		r->idiag_timer = SCTP_EVENT_TIMEOUT_T3_RTX;
+		r->idiag_retrans = asoc->rtx_data_chunks;
+		r->idiag_expires = jiffies_to_msecs(t3_rtx->expires - jiffies);
+	} else {
+		r->idiag_timer = 0;
+		r->idiag_retrans = 0;
+		r->idiag_expires = 0;
+	}
 }
 
 static int inet_diag_msg_sctpladdrs_fill(struct sk_buff *skb,
-- 
2.8.2