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53 lines
2.2 KiB
Diff
53 lines
2.2 KiB
Diff
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From a024e377efed31ecfb39210bed562932321345b3 Mon Sep 17 00:00:00 2001
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From: Antonio Pastor <antonio.pastor@gmail.com>
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Date: Tue, 24 Dec 2024 20:07:20 -0500
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Subject: [PATCH] net: llc: reset skb->transport_header
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802.2+LLC+SNAP frames received by napi_complete_done with GRO and DSA
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have skb->transport_header set two bytes short, or pointing 2 bytes
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before network_header & skb->data. As snap_rcv expects transport_header
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to point to SNAP header (OID:PID) after LLC processing advances offset
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over LLC header (llc_rcv & llc_fixup_skb), code doesn't find a match
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and packet is dropped.
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Between napi_complete_done and snap_rcv, transport_header is not used
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until __netif_receive_skb_core, where originally it was being reset.
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Commit fda55eca5a33 ("net: introduce skb_transport_header_was_set()")
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only does so if not set, on the assumption the value was set correctly
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by GRO (and also on assumption that "network stacks usually reset the
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transport header anyway"). Afterwards it is moved forward by
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llc_fixup_skb.
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Locally generated traffic shows up at __netif_receive_skb_core with no
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transport_header set and is processed without issue. On a setup with
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GRO but no DSA, transport_header and network_header are both set to
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point to skb->data which is also correct.
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As issue is LLC specific, to avoid impacting non-LLC traffic, and to
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follow up on original assumption made on previous code change,
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llc_fixup_skb to reset the offset after skb pull. llc_fixup_skb
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assumes the LLC header is at skb->data, and by definition SNAP header
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immediately follows.
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Fixes: fda55eca5a33 ("net: introduce skb_transport_header_was_set()")
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Signed-off-by: Antonio Pastor <antonio.pastor@gmail.com>
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Reviewed-by: Eric Dumazet <edumazet@google.com>
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Link: https://patch.msgid.link/20241225010723.2830290-1-antonio.pastor@gmail.com
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Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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---
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net/llc/llc_input.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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--- a/net/llc/llc_input.c
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+++ b/net/llc/llc_input.c
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@@ -124,8 +124,8 @@ static inline int llc_fixup_skb(struct s
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if (unlikely(!pskb_may_pull(skb, llc_len)))
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return 0;
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- skb->transport_header += llc_len;
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skb_pull(skb, llc_len);
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+ skb_reset_transport_header(skb);
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if (skb->protocol == htons(ETH_P_802_2)) {
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__be16 pdulen;
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s32 data_size;
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