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In the case where a non-MPLS packet is received and an MPLS stack is added it may well be the case that the original skb is GSO but the NIC used for transmit does not support GSO of MPLS packets. The aim of this code is to provide GSO in software for MPLS packets whose skbs are GSO. SKB Usage: When an implementation adds an MPLS stack to a non-MPLS packet it should do the following to skb metadata: * Set skb->inner_protocol to the old non-MPLS ethertype of the packet. skb->inner_protocol is added by this patch. * Set skb->protocol to the new MPLS ethertype of the packet. * Set skb->network_header to correspond to the end of the L3 header, including the MPLS label stack. I have posted a patch, "[PATCH v3.29] datapath: Add basic MPLS support to kernel" which adds MPLS support to the kernel datapath of Open vSwtich. That patch sets the above requirements in datapath/actions.c:push_mpls() and was used to exercise this code. The datapath patch is against the Open vSwtich tree but it is intended that it be added to the Open vSwtich code present in the mainline Linux kernel at some point. Features: I believe that the approach that I have taken is at least partially consistent with the handling of other protocols. Jesse, I understand that you have some ideas here. I am more than happy to change my implementation. This patch adds dev->mpls_features which may be used by devices to advertise features supported for MPLS packets. A new NETIF_F_MPLS_GSO feature is added for devices which support hardware MPLS GSO offload. Currently no devices support this and MPLS GSO always falls back to software. Alternate Implementation: One possible alternate implementation is to teach netif_skb_features() and skb_network_protocol() about MPLS, in a similar way to their understanding of VLANs. I believe this would avoid the need for net/mpls/mpls_gso.c and in particular the calls to __skb_push() and __skb_push() in mpls_gso_segment(). I have decided on the implementation in this patch as it should not introduce any overhead in the case where mpls_gso is not compiled into the kernel or inserted as a module. MPLS GSO suggested by Jesse Gross. Based in part on "v4 GRE: Add TCP segmentation offload for GRE" by Pravin B Shelar. Cc: Jesse Gross <jesse@nicira.com> Cc: Pravin B Shelar <pshelar@nicira.com> Signed-off-by: Simon Horman <horms@verge.net.au> Signed-off-by: David S. Miller <davem@davemloft.net>
109 lines
2.6 KiB
C
109 lines
2.6 KiB
C
/*
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* MPLS GSO Support
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*
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* Authors: Simon Horman (horms@verge.net.au)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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* Based on: GSO portions of net/ipv4/gre.c
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/err.h>
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#include <linux/module.h>
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#include <linux/netdev_features.h>
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#include <linux/netdevice.h>
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#include <linux/skbuff.h>
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static struct sk_buff *mpls_gso_segment(struct sk_buff *skb,
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netdev_features_t features)
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{
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struct sk_buff *segs = ERR_PTR(-EINVAL);
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netdev_features_t mpls_features;
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__be16 mpls_protocol;
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if (unlikely(skb_shinfo(skb)->gso_type &
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~(SKB_GSO_TCPV4 |
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SKB_GSO_TCPV6 |
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SKB_GSO_UDP |
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SKB_GSO_DODGY |
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SKB_GSO_TCP_ECN |
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SKB_GSO_GRE |
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SKB_GSO_MPLS)))
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goto out;
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/* Setup inner SKB. */
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mpls_protocol = skb->protocol;
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skb->protocol = skb->inner_protocol;
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/* Push back the mac header that skb_mac_gso_segment() has pulled.
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* It will be re-pulled by the call to skb_mac_gso_segment() below
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*/
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__skb_push(skb, skb->mac_len);
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/* Segment inner packet. */
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mpls_features = skb->dev->mpls_features & netif_skb_features(skb);
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segs = skb_mac_gso_segment(skb, mpls_features);
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/* Restore outer protocol. */
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skb->protocol = mpls_protocol;
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/* Re-pull the mac header that the call to skb_mac_gso_segment()
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* above pulled. It will be re-pushed after returning
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* skb_mac_gso_segment(), an indirect caller of this function.
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*/
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__skb_push(skb, skb->data - skb_mac_header(skb));
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out:
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return segs;
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}
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static int mpls_gso_send_check(struct sk_buff *skb)
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{
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return 0;
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}
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static struct packet_offload mpls_mc_offload = {
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.type = cpu_to_be16(ETH_P_MPLS_MC),
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.callbacks = {
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.gso_send_check = mpls_gso_send_check,
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.gso_segment = mpls_gso_segment,
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},
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};
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static struct packet_offload mpls_uc_offload = {
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.type = cpu_to_be16(ETH_P_MPLS_UC),
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.callbacks = {
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.gso_send_check = mpls_gso_send_check,
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.gso_segment = mpls_gso_segment,
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},
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};
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static int __init mpls_gso_init(void)
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{
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pr_info("MPLS GSO support\n");
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dev_add_offload(&mpls_uc_offload);
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dev_add_offload(&mpls_mc_offload);
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return 0;
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}
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static void __exit mpls_gso_exit(void)
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{
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dev_remove_offload(&mpls_uc_offload);
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dev_remove_offload(&mpls_mc_offload);
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}
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module_init(mpls_gso_init);
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module_exit(mpls_gso_exit);
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MODULE_DESCRIPTION("MPLS GSO support");
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MODULE_AUTHOR("Simon Horman (horms@verge.net.au)");
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MODULE_LICENSE("GPL");
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