On Wed, Oct 26, 2016 at 8:54 AM, David Lebrun <david.leb...@uclouvain.be> wrote:
> Implement minimal support for processing of SR-enabled packets
> as described in
> https://tools.ietf.org/html/draft-ietf-6man-segment-routing-header-02.
>
> 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>
> ---
> include/linux/ipv6.h | 1 +
> include/linux/seg6.h | 6 ++
> include/uapi/linux/ipv6.h | 2 +
> include/uapi/linux/seg6.h | 48 ++++++++++++
> net/ipv6/addrconf.c | 10 +++
> net/ipv6/exthdrs.c | 183
> ++++++++++++++++++++++++++++++++++++++++++++++
> 6 files changed, 250 insertions(+)
> create mode 100644 include/linux/seg6.h
> create mode 100644 include/uapi/linux/seg6.h
>
> diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
> index 7e9a789..76830e6 100644
> --- a/include/linux/ipv6.h
> +++ b/include/linux/ipv6.h
> @@ -64,6 +64,7 @@ struct ipv6_devconf {
> } stable_secret;
> __s32 use_oif_addrs_only;
> __s32 keep_addr_on_down;
> + __s32 seg6_enabled;
>
> struct ctl_table_header *sysctl_header;
> };
> diff --git a/include/linux/seg6.h b/include/linux/seg6.h
> new file mode 100644
> index 0000000..7a66d2b
> --- /dev/null
> +++ b/include/linux/seg6.h
> @@ -0,0 +1,6 @@
> +#ifndef _LINUX_SEG6_H
> +#define _LINUX_SEG6_H
> +
> +#include <uapi/linux/seg6.h>
> +
> +#endif
> diff --git a/include/uapi/linux/ipv6.h b/include/uapi/linux/ipv6.h
> index 8c27723..7ff1d65 100644
> --- a/include/uapi/linux/ipv6.h
> +++ b/include/uapi/linux/ipv6.h
> @@ -39,6 +39,7 @@ struct in6_ifreq {
> #define IPV6_SRCRT_STRICT 0x01 /* Deprecated; will be removed */
> #define IPV6_SRCRT_TYPE_0 0 /* Deprecated; will be removed */
> #define IPV6_SRCRT_TYPE_2 2 /* IPv6 type 2 Routing Header */
> +#define IPV6_SRCRT_TYPE_4 4 /* Segment Routing with IPv6 */
>
> /*
> * routing header
> @@ -178,6 +179,7 @@ enum {
> DEVCONF_DROP_UNSOLICITED_NA,
> DEVCONF_KEEP_ADDR_ON_DOWN,
> DEVCONF_RTR_SOLICIT_MAX_INTERVAL,
> + DEVCONF_SEG6_ENABLED,
> DEVCONF_MAX
> };
>
> diff --git a/include/uapi/linux/seg6.h b/include/uapi/linux/seg6.h
> new file mode 100644
> index 0000000..7630e7d
> --- /dev/null
> +++ b/include/uapi/linux/seg6.h
> @@ -0,0 +1,48 @@
> +/*
> + * SR-IPv6 implementation
> + *
> + * Author:
> + * David Lebrun <david.leb...@uclouvain.be>
> + *
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; either version
> + * 2 of the License, or (at your option) any later version.
> + */
> +
> +#ifndef _UAPI_LINUX_SEG6_H
> +#define _UAPI_LINUX_SEG6_H
> +
> +/*
> + * SRH
> + */
> +struct ipv6_sr_hdr {
> + __u8 nexthdr;
> + __u8 hdrlen;
> + __u8 type;
> + __u8 segments_left;
> + __u8 first_segment;
> + __u8 flag_1;
> + __u8 flag_2;
> + __u8 reserved;
> +
> + struct in6_addr segments[0];
> +};
> +
> +#define SR6_FLAG1_CLEANUP (1 << 7)
> +#define SR6_FLAG1_PROTECTED (1 << 6)
> +#define SR6_FLAG1_OAM (1 << 5)
> +#define SR6_FLAG1_ALERT (1 << 4)
> +#define SR6_FLAG1_HMAC (1 << 3)
> +
> +#define SR6_TLV_INGRESS 1
> +#define SR6_TLV_EGRESS 2
> +#define SR6_TLV_OPAQUE 3
> +#define SR6_TLV_PADDING 4
> +#define SR6_TLV_HMAC 5
> +
> +#define sr_has_cleanup(srh) ((srh)->flag_1 & SR6_FLAG1_CLEANUP)
> +#define sr_has_hmac(srh) ((srh)->flag_1 & SR6_FLAG1_HMAC)
> +
> +#endif
> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> index d8983e1..8d068ee 100644
> --- a/net/ipv6/addrconf.c
> +++ b/net/ipv6/addrconf.c
> @@ -239,6 +239,7 @@ static struct ipv6_devconf ipv6_devconf __read_mostly = {
> .use_oif_addrs_only = 0,
> .ignore_routes_with_linkdown = 0,
> .keep_addr_on_down = 0,
> + .seg6_enabled = 0,
> };
>
> static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = {
> @@ -285,6 +286,7 @@ static struct ipv6_devconf ipv6_devconf_dflt
> __read_mostly = {
> .use_oif_addrs_only = 0,
> .ignore_routes_with_linkdown = 0,
> .keep_addr_on_down = 0,
> + .seg6_enabled = 0,
> };
>
> /* Check if a valid qdisc is available */
> @@ -4965,6 +4967,7 @@ static inline void ipv6_store_devconf(struct
> ipv6_devconf *cnf,
> array[DEVCONF_DROP_UNICAST_IN_L2_MULTICAST] =
> cnf->drop_unicast_in_l2_multicast;
> array[DEVCONF_DROP_UNSOLICITED_NA] = cnf->drop_unsolicited_na;
> array[DEVCONF_KEEP_ADDR_ON_DOWN] = cnf->keep_addr_on_down;
> + array[DEVCONF_SEG6_ENABLED] = cnf->seg6_enabled;
> }
>
> static inline size_t inet6_ifla6_size(void)
> @@ -6057,6 +6060,13 @@ static const struct ctl_table addrconf_sysctl[] = {
>
> },
> {
> + .procname = "seg6_enabled",
> + .data = &ipv6_devconf.seg6_enabled,
> + .maxlen = sizeof(int),
> + .mode = 0644,
> + .proc_handler = proc_dointvec,
> + },
> + {
> /* sentinel */
> }
> };
> diff --git a/net/ipv6/exthdrs.c b/net/ipv6/exthdrs.c
> index 139ceb6..cf9f338 100644
> --- a/net/ipv6/exthdrs.c
> +++ b/net/ipv6/exthdrs.c
> @@ -47,6 +47,7 @@
> #if IS_ENABLED(CONFIG_IPV6_MIP6)
> #include <net/xfrm.h>
> #endif
> +#include <linux/seg6.h>
>
> #include <linux/uaccess.h>
>
> @@ -286,6 +287,184 @@ static int ipv6_destopt_rcv(struct sk_buff *skb)
> return -1;
> }
>
> +static inline void update_csum_diff4(struct sk_buff *skb, __be32 from,
> + __be32 to)
> +{
> + __be32 diff[] = { ~from, to };
> +
> + skb->csum = ~csum_partial((char *)diff, sizeof(diff), ~skb->csum);
> +}
> +
> +static inline void update_csum_diff16(struct sk_buff *skb, __be32 *from,
> + __be32 *to)
> +{
> + __be32 diff[] = {
> + ~from[0], ~from[1], ~from[2], ~from[3],
> + to[0], to[1], to[2], to[3],
> + };
> +
> + skb->csum = ~csum_partial((char *)diff, sizeof(diff), ~skb->csum);
> +}
These should be in a common header file.
> +
> +static void seg6_update_csum(struct sk_buff *skb)
> +{
> + struct ipv6_sr_hdr *hdr;
> + struct in6_addr *addr;
> + __be32 from, to;
> +
> + /* srh is at transport offset and seg_left is already decremented
> + * but daddr is not yet updated with next segment
> + */
> +
> + hdr = (struct ipv6_sr_hdr *)skb_transport_header(skb);
> + addr = hdr->segments + hdr->segments_left;
> +
> + hdr->segments_left++;
> + from = *(__be32 *)hdr;
> +
> + hdr->segments_left--;
> + to = *(__be32 *)hdr;
> +
> + /* update skb csum with diff resulting from seg_left decrement */
> +
> + update_csum_diff4(skb, from, to);
> +
> + /* compute csum diff between current and next segment and update */
> +
> + update_csum_diff16(skb, (__be32 *)(&ipv6_hdr(skb)->daddr),
> + (__be32 *)addr);
> +}
NIce. Have you tested that checksum offload works if the penultimate
and final addresses are in same host?
> +
> +static int ipv6_srh_rcv(struct sk_buff *skb)
> +{
> + struct inet6_skb_parm *opt = IP6CB(skb);
> + struct net *net = dev_net(skb->dev);
> + struct ipv6_sr_hdr *hdr;
> + struct inet6_dev *idev;
> + struct in6_addr *addr;
> + int cleanup = 0;
Should be a bool?
> + int accept_seg6;
> +
> + 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:
> + if (hdr->segments_left > 0) {
> + if (hdr->nexthdr != NEXTHDR_IPV6 && hdr->segments_left == 1 &&
> + sr_has_cleanup(hdr))
> + cleanup = 1;
> + } else {
> + if (hdr->nexthdr == NEXTHDR_IPV6) {
> + int offset = (hdr->hdrlen + 1) << 3;
> +
> + skb_postpull_rcsum(skb, skb_network_header(skb),
> + skb_network_header_len(skb));
> +
> + 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;
> + }
> + }
> +
> + hdr = (struct ipv6_sr_hdr *)skb_transport_header(skb);
> +
> + hdr->segments_left--;
> + addr = hdr->segments + hdr->segments_left;
> +
> + skb_push(skb, sizeof(struct ipv6hdr));
> +
> + if (skb->ip_summed == CHECKSUM_COMPLETE)
> + seg6_update_csum(skb);
> +
> + ipv6_hdr(skb)->daddr = *addr;
> +
> + if (cleanup) {
> + int srhlen = (hdr->hdrlen + 1) << 3;
> + int nh = hdr->nexthdr;
> +
> + skb_pull_rcsum(skb, sizeof(struct ipv6hdr) + srhlen);
> + memmove(skb_network_header(skb) + srhlen,
> + skb_network_header(skb),
> + (unsigned char *)hdr - skb_network_header(skb));
> + skb->network_header += srhlen;
> + ipv6_hdr(skb)->nexthdr = nh;
> + ipv6_hdr(skb)->payload_len = htons(skb->len -
> + sizeof(struct ipv6hdr));
> + skb_push_rcsum(skb, sizeof(struct ipv6hdr));
> + }
> +
> + skb_dst_drop(skb);
> +
> + ip6_route_input(skb);
> +
> + if (skb_dst(skb)->error) {
> + dst_input(skb);
> + return -1;
> + }
> +
> + if (skb_dst(skb)->dev->flags & IFF_LOOPBACK) {
> + if (ipv6_hdr(skb)->hop_limit <= 1) {
> + __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
> + IPSTATS_MIB_INHDRERRORS);
> + icmpv6_send(skb, ICMPV6_TIME_EXCEED,
> + ICMPV6_EXC_HOPLIMIT, 0);
> + kfree_skb(skb);
> + return -1;
> + }
> + ipv6_hdr(skb)->hop_limit--;
> +
> + /* be sure that srh is still present before reinjecting */
> + if (!cleanup) {
> + skb_pull(skb, sizeof(struct ipv6hdr));
> + goto looped_back;
> + }
> + skb_set_transport_header(skb, sizeof(struct ipv6hdr));
> + IP6CB(skb)->nhoff = offsetof(struct ipv6hdr, nexthdr);
> + }
> +
> + dst_input(skb);
> +
> + return -1;
> +}
> +
> /********************************
> Routing header.
> ********************************/
> @@ -326,6 +505,10 @@ static int ipv6_rthdr_rcv(struct sk_buff *skb)
> return -1;
> }
>
> + /* segment routing */
> + if (hdr->type == IPV6_SRCRT_TYPE_4)
> + return ipv6_srh_rcv(skb);
> +
> looped_back:
> if (hdr->segments_left == 0) {
> switch (hdr->type) {
> --
> 2.7.3
>
Acked-by: Tom Herbert <t...@herberland.com>
