From 1ababeba4a21f3dba3da3523c670b207fb2feb62 Mon Sep 17 00:00:00 2001 From: David Lebrun Date: Tue, 8 Nov 2016 14:57:39 +0100 Subject: [PATCH] ipv6: implement dataplane support for rthdr type 4 (Segment Routing Header) 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 Signed-off-by: David S. Miller --- include/linux/ipv6.h | 1 + include/linux/seg6.h | 6 ++ include/net/seg6.h | 36 ++++++++ include/uapi/linux/ipv6.h | 2 + include/uapi/linux/seg6.h | 54 ++++++++++++ net/ipv6/addrconf.c | 10 +++ net/ipv6/exthdrs.c | 175 ++++++++++++++++++++++++++++++++++++++ 7 files changed, 284 insertions(+) create mode 100644 include/linux/seg6.h create mode 100644 include/net/seg6.h create mode 100644 include/uapi/linux/seg6.h diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h index 1afb6e8d35c3..68d3f71f0abf 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 000000000000..7a66d2b4c5a6 --- /dev/null +++ b/include/linux/seg6.h @@ -0,0 +1,6 @@ +#ifndef _LINUX_SEG6_H +#define _LINUX_SEG6_H + +#include + +#endif diff --git a/include/net/seg6.h b/include/net/seg6.h new file mode 100644 index 000000000000..4dd52a7e95f1 --- /dev/null +++ b/include/net/seg6.h @@ -0,0 +1,36 @@ +/* + * SR-IPv6 implementation + * + * Author: + * David Lebrun + * + * + * 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 _NET_SEG6_H +#define _NET_SEG6_H + +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); +} + +#endif diff --git a/include/uapi/linux/ipv6.h b/include/uapi/linux/ipv6.h index 8c2772340c3f..7ff1d654e333 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 000000000000..c396a8052f73 --- /dev/null +++ b/include/uapi/linux/seg6.h @@ -0,0 +1,54 @@ +/* + * SR-IPv6 implementation + * + * Author: + * David Lebrun + * + * + * 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) + +struct sr6_tlv { + __u8 type; + __u8 len; + __u8 data[0]; +}; + +#endif diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c index 060dd9922018..2ac6cb460af0 100644 --- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -238,6 +238,7 @@ 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 = { @@ -284,6 +285,7 @@ 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 */ @@ -4944,6 +4946,7 @@ 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) @@ -6035,6 +6038,13 @@ static const struct ctl_table addrconf_sysctl[] = { .proc_handler = proc_dointvec, }, + { + .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 139ceb68bd37..b8ba3961ff8a 100644 --- a/net/ipv6/exthdrs.c +++ b/net/ipv6/exthdrs.c @@ -47,6 +47,8 @@ #if IS_ENABLED(CONFIG_IPV6_MIP6) #include #endif +#include +#include #include @@ -286,6 +288,175 @@ static int ipv6_destopt_rcv(struct sk_buff *skb) return -1; } +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); +} + +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; + bool cleanup = false; + 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 = true; + } 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 (hdr->segments_left >= (hdr->hdrlen >> 1)) { + __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)), + IPSTATS_MIB_INHDRERRORS); + icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, + ((&hdr->segments_left) - + skb_network_header(skb))); + kfree_skb(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 +497,10 @@ 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) { -- GitLab