Commit 667aa742 authored by Johannes Berg's avatar Johannes Berg
Browse files

cfg80211/mac80211: assume CHECKSUM_COMPLETE includes SNAP 



There's currently only one driver that reports CHECKSUM_COMPLETE,
that is iwlwifi. The current hardware there calculates checksum
after the SNAP header, but only RFC 1042 (and some other cases,
but replicating the exact hardware logic for corner cases in the
driver seemed awkward.)

Newer generations of hardware will checksum _including_ the SNAP,
which makes things easier.

To handle that, simply always assume the checksum _includes_ the
SNAP header, which this patch does, requiring to first add it
for older iwlwifi hardware, and then remove it again later on
conversion.

Alternatively, we could have:

 1) Always assumed the checksum starts _after_ the SNAP header;
    the problem with this is that we'd have to replace the exact
    "what is the SNAP" check in iwlwifi that cfg80211 has.

 2) Made it configurable with some flag, but that seemed like too
    much complexity.

Signed-off-by: default avatarJohannes Berg <johannes.berg@intel.com>
Signed-off-by: default avatarLuca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20220202104617.230736e19e0e.I3e6745873585ad943c152fab9e23b5221f17a95f@changeid


Signed-off-by: default avatarJohannes Berg <johannes.berg@intel.com>
parent f39b7d62

drivers/net/wireless/intel/iwlwifi/mvm/rxmq.c

+3 −0
Original line number Diff line number Diff line
@@ -209,6 +209,9 @@ static int iwl_mvm_create_skb(struct iwl_mvm *mvm, struct sk_buff *skb, 
			      shdr->type != htons(ETH_P_PAE) &&

			      shdr->type != htons(ETH_P_TDLS))))

			skb->ip_summed = CHECKSUM_NONE;

		else

			/* mac80211 assumes full CSUM including SNAP header */

			skb_postpush_rcsum(skb, shdr, sizeof(*shdr));

	}



	fraglen = len - headlen;

net/mac80211/rx.c

+2 −0
Original line number Diff line number Diff line
@@ -4629,6 +4629,8 @@ static bool ieee80211_invoke_fast_rx(struct ieee80211_rx_data *rx, 
	/* do the header conversion - first grab the addresses */

	ether_addr_copy(addrs.da, skb->data + fast_rx->da_offs);

	ether_addr_copy(addrs.sa, skb->data + fast_rx->sa_offs);

	skb_postpull_rcsum(skb, skb->data + snap_offs,

			   sizeof(rfc1042_header) + 2);

	/* remove the SNAP but leave the ethertype */

	skb_pull(skb, snap_offs + sizeof(rfc1042_header));

	/* push the addresses in front */

net/wireless/util.c

+5 −3
Original line number Diff line number Diff line
@@ -5,7 +5,7 @@ 
 * Copyright 2007-2009	Johannes Berg <johannes@sipsolutions.net>

 * Copyright 2013-2014  Intel Mobile Communications GmbH

 * Copyright 2017	Intel Deutschland GmbH

 * Copyright (C) 2018-2020 Intel Corporation

 * Copyright (C) 2018-2021 Intel Corporation

 */

#include <linux/export.h>

#include <linux/bitops.h>
@@ -634,12 +634,14 @@ int ieee80211_data_to_8023_exthdr(struct sk_buff *skb, struct ethhdr *ehdr, 
	if (likely((!is_amsdu && ether_addr_equal(payload.hdr, rfc1042_header) &&

		    tmp.h_proto != htons(ETH_P_AARP) &&

		    tmp.h_proto != htons(ETH_P_IPX)) ||

		   ether_addr_equal(payload.hdr, bridge_tunnel_header)))

		   ether_addr_equal(payload.hdr, bridge_tunnel_header))) {

		/* remove RFC1042 or Bridge-Tunnel encapsulation and

		 * replace EtherType */

		hdrlen += ETH_ALEN + 2;

	else

		skb_postpull_rcsum(skb, &payload, ETH_ALEN + 2);

	} else {

		tmp.h_proto = htons(skb->len - hdrlen);

	}



	pskb_pull(skb, hdrlen);