From d549699048b4b5c22dd710455bcdb76966e55aa3 Mon Sep 17 00:00:00 2001 From: Eyal Birger Date: Sat, 21 Nov 2020 08:28:17 +0200 Subject: [PATCH] net/packet: fix packet receive on L3 devices without visible hard header In the patchset merged by commit b9fcf0a0d826 ("Merge branch 'support-AF_PACKET-for-layer-3-devices'") L3 devices which did not have header_ops were given one for the purpose of protocol parsing on af_packet transmit path. That change made af_packet receive path regard these devices as having a visible L3 header and therefore aligned incoming skb->data to point to the skb's mac_header. Some devices, such as ipip, xfrmi, and others, do not reset their mac_header prior to ingress and therefore their incoming packets became malformed. Ideally these devices would reset their mac headers, or af_packet would be able to rely on dev->hard_header_len being 0 for such cases, but it seems this is not the case. Fix by changing af_packet RX ll visibility criteria to include the existence of a '.create()' header operation, which is used when creating a device hard header - via dev_hard_header() - by upper layers, and does not exist in these L3 devices. As this predicate may be useful in other situations, add it as a common dev_has_header() helper in netdevice.h. Fixes: b9fcf0a0d826 ("Merge branch 'support-AF_PACKET-for-layer-3-devices'") Signed-off-by: Eyal Birger Acked-by: Jason A. Donenfeld Acked-by: Willem de Bruijn Link: https://lore.kernel.org/r/20201121062817.3178900-1-eyal.birger@gmail.com Signed-off-by: Jakub Kicinski --- include/linux/netdevice.h | 5 +++++ net/packet/af_packet.c | 18 +++++++++--------- 2 files changed, 14 insertions(+), 9 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 964b494b0e8d..fa275a054f46 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -3137,6 +3137,11 @@ static inline bool dev_validate_header(const struct net_device *dev, return false; } +static inline bool dev_has_header(const struct net_device *dev) +{ + return dev->header_ops && dev->header_ops->create; +} + typedef int gifconf_func_t(struct net_device * dev, char __user * bufptr, int len, int size); int register_gifconf(unsigned int family, gifconf_func_t *gifconf); diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index cefbd50c1090..7a18ffff8551 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -93,8 +93,8 @@ /* Assumptions: - - If the device has no dev->header_ops, there is no LL header visible - above the device. In this case, its hard_header_len should be 0. + - If the device has no dev->header_ops->create, there is no LL header + visible above the device. In this case, its hard_header_len should be 0. The device may prepend its own header internally. In this case, its needed_headroom should be set to the space needed for it to add its internal header. @@ -108,26 +108,26 @@ On receive: ----------- -Incoming, dev->header_ops != NULL +Incoming, dev_has_header(dev) == true mac_header -> ll header data -> data -Outgoing, dev->header_ops != NULL +Outgoing, dev_has_header(dev) == true mac_header -> ll header data -> ll header -Incoming, dev->header_ops == NULL +Incoming, dev_has_header(dev) == false mac_header -> data However drivers often make it point to the ll header. This is incorrect because the ll header should be invisible to us. data -> data -Outgoing, dev->header_ops == NULL +Outgoing, dev_has_header(dev) == false mac_header -> data. ll header is invisible to us. data -> data Resume - If dev->header_ops == NULL we are unable to restore the ll header, + If dev_has_header(dev) == false we are unable to restore the ll header, because it is invisible to us. @@ -2069,7 +2069,7 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev, skb->dev = dev; - if (dev->header_ops) { + if (dev_has_header(dev)) { /* The device has an explicit notion of ll header, * exported to higher levels. * @@ -2198,7 +2198,7 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev, if (!net_eq(dev_net(dev), sock_net(sk))) goto drop; - if (dev->header_ops) { + if (dev_has_header(dev)) { if (sk->sk_type != SOCK_DGRAM) skb_push(skb, skb->data - skb_mac_header(skb)); else if (skb->pkt_type == PACKET_OUTGOING) {