Commit 1ababeba authored by David Lebrun's avatar David Lebrun Committed by David S. Miller
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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: default avatarDavid Lebrun <david.lebrun@uclouvain.be>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent dc0b2c9c
......@@ -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;
};
......
#ifndef _LINUX_SEG6_H
#define _LINUX_SEG6_H
#include <uapi/linux/seg6.h>
#endif
/*
* SR-IPv6 implementation
*
* Author:
* David Lebrun <david.lebrun@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 _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
......@@ -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
};
......
/*
* SR-IPv6 implementation
*
* Author:
* David Lebrun <david.lebrun@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)
struct sr6_tlv {
__u8 type;
__u8 len;
__u8 data[0];
};
#endif
......@@ -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 */
}
......
......@@ -47,6 +47,8 @@
#if IS_ENABLED(CONFIG_IPV6_MIP6)
#include <net/xfrm.h>
#endif
#include <linux/seg6.h>
#include <net/seg6.h>
#include <linux/uaccess.h>
......@@ -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) {
......
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