Le 26/08/2016 à 17:52, David Lebrun a écrit :
> Implement minimal support for processing of SR-enabled packets
> as described in
> https://tools.ietf.org/html/draft-ietf-6man-segment-routing-header-01.
>
> This patch implements the following operations:
> - Intermediate segment endpoint: incrementation of active segment and
> rerouting.
> - Egress for SR-encapsulated packets: decapsulation of outer IPv6 header + SRH
> and routing of inner packet.
> - Cleanup flag support for SR-inlined packets: removal of SRH if we are the
> penultimate segment endpoint.
>
> A per-interface sysctl seg6_enabled is provided, to accept/deny SR-enabled
> packets. Default is deny.
>
> This patch does not provide support for HMAC-signed packets.
>
> Signed-off-by: David Lebrun <david.leb...@uclouvain.be>
> ---
Thanks for proposing this feature. It would be great to have it upstream.
[snip]
> +config IPV6_SEG6
> + bool "IPv6: Segment Routing support"
> + depends on IPV6
> + ---help---
> + Experimental support for IPv6 Segment Routing dataplane as defined
> + in IETF draft-ietf-6man-segment-routing-header-01. This option
> + enables the processing of SR-enabled packets allowing the kernel
> + to act as a segment endpoint (intermediate or egress).
> +
> + If unsure, say N.
> +
I don't think that the option is needed. At the end, every distributions will
turn it on.
[snip]
> +#ifdef CONFIG_IPV6_SEG6
> + {
> + .procname = "seg6_enabled",
> + .data = &ipv6_devconf.seg6_enabled,
> + .maxlen = sizeof(int),
> + .mode = 0644,
> + .proc_handler = proc_dointvec,
> + },
> +#endif
Don't forget to document this option in Documentation/networking/ip-sysctl.txt.
Don't forget to explain how 'all' works ;-)
It would be nice to also add it in netconf subsystem (see 'git grep netconf
net/ipv6').
[snip]
> +#ifdef CONFIG_IPV6_SEG6
> +static int ipv6_srh_rcv(struct sk_buff *skb)
> +{
> + struct inet6_skb_parm *opt = IP6CB(skb);
> + struct in6_addr *addr = NULL, *last_addr = NULL, *active_addr = NULL;
> + struct ipv6_sr_hdr *hdr;
> + struct net *net = dev_net(skb->dev);
> + int cleanup = 0;
> + struct inet6_dev *idev;
> + int accept_seg6;
nit: better to follow the 'reverse christmas tree' scheme when declaring
variables.
> +
> + hdr = (struct ipv6_sr_hdr *)skb_transport_header(skb);
> +
> + idev = __in6_dev_get(skb->dev);
> +
> + accept_seg6 = net->ipv6.devconf_all->seg6_enabled;
> + if (accept_seg6 > idev->cnf.seg6_enabled)
> + accept_seg6 = idev->cnf.seg6_enabled;
> +
> + if (!accept_seg6) {
> + kfree_skb(skb);
> + return -1;
> + }
> +
> +looped_back:
> + last_addr = hdr->segments;
> +
> + if (hdr->segments_left > 0) {
> + if (hdr->nexthdr != NEXTHDR_IPV6 && hdr->segments_left == 1 &&
> + sr_get_flags(hdr) & SR6_FLAG_CLEANUP)
> + cleanup = 1;
> + } else {
> + if (hdr->nexthdr == NEXTHDR_IPV6) {
> + int offset = (hdr->hdrlen + 1) << 3;
> +
> + if (!pskb_pull(skb, offset)) {
> + kfree_skb(skb);
> + return -1;
> + }
> + skb_postpull_rcsum(skb, skb_transport_header(skb),
> + offset);
> +
> + skb_reset_network_header(skb);
> + skb_reset_transport_header(skb);
> + skb->encapsulation = 0;
> +
> + __skb_tunnel_rx(skb, skb->dev, net);
> +
> + netif_rx(skb);
> + return -1;
> + }
> +
> + opt->srcrt = skb_network_header_len(skb);
> + opt->lastopt = opt->srcrt;
> + skb->transport_header += (hdr->hdrlen + 1) << 3;
> + opt->nhoff = (&hdr->nexthdr) - skb_network_header(skb);
> +
> + return 1;
> + }
> +
> + if (skb_cloned(skb)) {
> + if (pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) {
> + __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
> + IPSTATS_MIB_OUTDISCARDS);
> + kfree_skb(skb);
> + return -1;
> + }
> + }
> +
> + if (skb->ip_summed == CHECKSUM_COMPLETE)
> + skb->ip_summed = CHECKSUM_NONE;
> +
> + hdr = (struct ipv6_sr_hdr *)skb_transport_header(skb);
> +
> + active_addr = hdr->segments + hdr->segments_left;
> + hdr->segments_left--;
> + addr = hdr->segments + hdr->segments_left;
> +
> + ipv6_hdr(skb)->daddr = *addr;
> +
> + skb_push(skb, sizeof(struct ipv6hdr));
> +
> + /* cleanup */
> +
> + if (cleanup) {
> + int srhlen = (hdr->hdrlen + 1) << 3;
> + int nh = hdr->nexthdr;
> +
> + memmove(skb_network_header(skb) + srhlen,
> + skb_network_header(skb),
> + (unsigned char *)hdr - skb_network_header(skb));
> + skb_pull(skb, srhlen);
> + skb->network_header += srhlen;
> + ipv6_hdr(skb)->nexthdr = nh;
> + ipv6_hdr(skb)->payload_len = htons(skb->len -
> + sizeof(struct ipv6hdr));
> + }
> +
> + skb_dst_drop(skb);
> +
> + ip6_route_input(skb);
The destination address has now changed and the packet is routed again.
skb->nfct is not updated, it is intentional? I'm asking me if it's conceptually
right.
