[PATCH can-next v2 3/6] can: move ifindex to CAN skb extensions
From: Marc Kleine-Budde
Date: Wed Jan 28 2026 - 04:31:10 EST
From: Oliver Hartkopp <socketcan@xxxxxxxxxxxx>
When routing CAN frames over different CAN interfaces the interface index
skb->iif is overwritten with every single hop. To prevent sending a CAN
frame back to its originating (first) incoming CAN interface another
ifindex variable is needed, which was stored in can_skb_priv::ifindex.
Move the can_skb_priv::ifindex content to can_skb_ext::can_iif.
Signed-off-by: Oliver Hartkopp <socketcan@xxxxxxxxxxxx>
---
drivers/net/can/dev/skb.c | 9 ++++-----
net/can/bcm.c | 4 ++--
net/can/gw.c | 2 +-
net/can/isotp.c | 6 +++---
net/can/j1939/socket.c | 2 +-
net/can/j1939/transport.c | 4 ++--
net/can/raw.c | 2 +-
7 files changed, 14 insertions(+), 15 deletions(-)
diff --git a/drivers/net/can/dev/skb.c b/drivers/net/can/dev/skb.c
index c572745565f6..470255fe7367 100644
--- a/drivers/net/can/dev/skb.c
+++ b/drivers/net/can/dev/skb.c
@@ -223,7 +223,7 @@ struct sk_buff *alloc_can_skb(struct net_device *dev, struct can_frame **cf)
skb->protocol = htons(ETH_P_CAN);
init_can_skb_reserve(skb);
- can_skb_prv(skb)->ifindex = dev->ifindex;
+ csx->can_iif = dev->ifindex;
*cf = skb_put_zero(skb, sizeof(struct can_frame));
@@ -255,7 +255,7 @@ struct sk_buff *alloc_canfd_skb(struct net_device *dev,
skb->protocol = htons(ETH_P_CANFD);
init_can_skb_reserve(skb);
- can_skb_prv(skb)->ifindex = dev->ifindex;
+ csx->can_iif = dev->ifindex;
*cfd = skb_put_zero(skb, sizeof(struct canfd_frame));
@@ -294,7 +294,7 @@ struct sk_buff *alloc_canxl_skb(struct net_device *dev,
skb->protocol = htons(ETH_P_CANXL);
init_can_skb_reserve(skb);
- can_skb_prv(skb)->ifindex = dev->ifindex;
+ csx->can_iif = dev->ifindex;
*cxl = skb_put_zero(skb, CANXL_HDR_SIZE + data_len);
@@ -344,8 +344,7 @@ static bool can_skb_headroom_valid(struct net_device *dev, struct sk_buff *skb)
return false;
}
- can_skb_prv(skb)->ifindex = dev->ifindex;
-
+ csx->can_iif = dev->ifindex;
skb->ip_summed = CHECKSUM_UNNECESSARY;
/* perform proper loopback on capable devices */
diff --git a/net/can/bcm.c b/net/can/bcm.c
index 38452069dea8..f102d17e8619 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -323,7 +323,7 @@ static void bcm_can_tx(struct bcm_op *op)
}
can_skb_reserve(skb);
- can_skb_prv(skb)->ifindex = dev->ifindex;
+ csx->can_iif = dev->ifindex;
skb_put_data(skb, cf, op->cfsiz);
@@ -1357,7 +1357,7 @@ static int bcm_tx_send(struct msghdr *msg, int ifindex, struct sock *sk,
return -ENODEV;
}
- can_skb_prv(skb)->ifindex = dev->ifindex;
+ csx->can_iif = dev->ifindex;
skb->dev = dev;
can_skb_set_owner(skb, sk);
err = can_send(skb, 1); /* send with loopback */
diff --git a/net/can/gw.c b/net/can/gw.c
index 8894ab5d2087..ad89a1913b34 100644
--- a/net/can/gw.c
+++ b/net/can/gw.c
@@ -505,7 +505,7 @@ static void can_can_gw_rcv(struct sk_buff *skb, void *data)
/* is sending the skb back to the incoming interface not allowed? */
if (!(gwj->flags & CGW_FLAGS_CAN_IIF_TX_OK) &&
- can_skb_prv(skb)->ifindex == gwj->dst.dev->ifindex)
+ csx->can_iif == gwj->dst.dev->ifindex)
return;
/* clone the given skb, which has not been done in can_rcv()
diff --git a/net/can/isotp.c b/net/can/isotp.c
index c4fb8afde165..01ceb3febbb7 100644
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -237,7 +237,7 @@ static int isotp_send_fc(struct sock *sk, int ae, u8 flowstatus)
}
can_skb_reserve(nskb);
- can_skb_prv(nskb)->ifindex = dev->ifindex;
+ csx->can_iif = dev->ifindex;
nskb->dev = dev;
can_skb_set_owner(nskb, sk);
@@ -794,7 +794,7 @@ static void isotp_send_cframe(struct isotp_sock *so)
}
can_skb_reserve(skb);
- can_skb_prv(skb)->ifindex = dev->ifindex;
+ csx->can_iif = dev->ifindex;
cf = (struct canfd_frame *)skb->data;
skb_put_zero(skb, so->ll.mtu);
@@ -1030,7 +1030,7 @@ static int isotp_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
}
can_skb_reserve(skb);
- can_skb_prv(skb)->ifindex = dev->ifindex;
+ csx->can_iif = dev->ifindex;
so->tx.len = size;
so->tx.idx = 0;
diff --git a/net/can/j1939/socket.c b/net/can/j1939/socket.c
index fc28a7677369..f03bae79354e 100644
--- a/net/can/j1939/socket.c
+++ b/net/can/j1939/socket.c
@@ -904,7 +904,7 @@ static struct sk_buff *j1939_sk_alloc_skb(struct net_device *ndev,
}
can_skb_reserve(skb);
- can_skb_prv(skb)->ifindex = ndev->ifindex;
+ csx->can_iif = ndev->ifindex;
skb_reserve(skb, offsetof(struct can_frame, data));
ret = memcpy_from_msg(skb_put(skb, size), msg, size);
diff --git a/net/can/j1939/transport.c b/net/can/j1939/transport.c
index 0514f3504e39..96e02ad4a726 100644
--- a/net/can/j1939/transport.c
+++ b/net/can/j1939/transport.c
@@ -608,7 +608,7 @@ sk_buff *j1939_tp_tx_dat_new(struct j1939_priv *priv,
skb->dev = priv->ndev;
can_skb_reserve(skb);
- can_skb_prv(skb)->ifindex = priv->ndev->ifindex;
+ csx->can_iif = priv->ndev->ifindex;
/* reserve CAN header */
skb_reserve(skb, offsetof(struct can_frame, data));
@@ -1549,7 +1549,7 @@ j1939_session *j1939_session_fresh_new(struct j1939_priv *priv,
skb->dev = priv->ndev;
can_skb_reserve(skb);
- can_skb_prv(skb)->ifindex = priv->ndev->ifindex;
+ csx->can_iif = priv->ndev->ifindex;
skcb = j1939_skb_to_cb(skb);
memcpy(skcb, rel_skcb, sizeof(*skcb));
diff --git a/net/can/raw.c b/net/can/raw.c
index 03438e9bc535..7c89962ec913 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -965,7 +965,7 @@ static int raw_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
}
can_skb_reserve(skb);
- can_skb_prv(skb)->ifindex = dev->ifindex;
+ csx->can_iif = dev->ifindex;
/* fill the skb before testing for valid CAN frames */
err = memcpy_from_msg(skb_put(skb, size), msg, size);
--
2.51.0