From 44218221b652b9f12feb5bf6404572dab07b3e03 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alexander=20H=C3=B6lzl?= <alexander.hoelzl@gmx.net>
Date: Wed, 5 Feb 2025 18:46:51 +0100
Subject: [PATCH] can: j1939: j1939_sk_send_loop(): fix unable to send messages
with data length zero
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
commit 44de577e61ed239db09f0da9d436866bef9b77dd upstream.
The J1939 standard requires the transmission of messages of length 0.
For example proprietary messages are specified with a data length of 0
to 1785. The transmission of such messages is not possible. Sending
results in no error being returned but no corresponding can frame
being generated.
Enable the transmission of zero length J1939 messages. In order to
facilitate this two changes are necessary:
1) If the transmission of a new message is requested from user space
the message is segmented in j1939_sk_send_loop(). Let the segmentation
take into account zero length messages, do not terminate immediately,
queue the corresponding skb.
2) j1939_session_skb_get_by_offset() selects the next skb to transmit
for a session. Take into account that there might be zero length skbs
in the queue.
Signed-off-by: Alexander Hölzl <alexander.hoelzl@gmx.net>
Acked-by: Oleksij Rempel <o.rempel@pengutronix.de>
Link: https://patch.msgid.link/20250205174651.103238-1-alexander.hoelzl@gmx.net
Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol")
Cc: stable@vger.kernel.org
[mkl: commit message rephrased]
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/can/j1939/socket.c | 4 ++--
net/can/j1939/transport.c | 5 +++--
2 files changed, 5 insertions(+), 4 deletions(-)
diff --git a/net/can/j1939/socket.c b/net/can/j1939/socket.c
index 58909b36561a6..0a4267a24263b 100644
--- a/net/can/j1939/socket.c
+++ b/net/can/j1939/socket.c
@@ -1132,7 +1132,7 @@ static int j1939_sk_send_loop(struct j1939_priv *priv, struct sock *sk,
todo_size = size;
- while (todo_size) {
+ do {
struct j1939_sk_buff_cb *skcb;
segment_size = min_t(size_t, J1939_MAX_TP_PACKET_SIZE,
@@ -1177,7 +1177,7 @@ static int j1939_sk_send_loop(struct j1939_priv *priv, struct sock *sk,
todo_size -= segment_size;
session->total_queued_size += segment_size;
- }
+ } while (todo_size);
switch (ret) {
case 0: /* OK */
diff --git a/net/can/j1939/transport.c b/net/can/j1939/transport.c
index a58f6f5dfcf8e..76d625c668e05 100644
--- a/net/can/j1939/transport.c
+++ b/net/can/j1939/transport.c
@@ -382,8 +382,9 @@ sk_buff *j1939_session_skb_get_by_offset(struct j1939_session *session,
skb_queue_walk(&session->skb_queue, do_skb) {
do_skcb = j1939_skb_to_cb(do_skb);
- if (offset_start >= do_skcb->offset &&
- offset_start < (do_skcb->offset + do_skb->len)) {
+ if ((offset_start >= do_skcb->offset &&
+ offset_start < (do_skcb->offset + do_skb->len)) ||
+ (offset_start == 0 && do_skcb->offset == 0 && do_skb->len == 0)) {
skb = do_skb;
}
}
--
GitLab