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/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 1afb6e8..68d3f71 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/net/seg6.h b/include/net/seg6.h
new file mode 100644
index 0000000..4dd52a7
--- /dev/null
+++ b/include/net/seg6.h
@@ -0,0 +1,36 @@
+/*
+ * 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 _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 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..c396a80
--- /dev/null
+++ b/include/uapi/linux/seg6.h
@@ -0,0 +1,54 @@
+/*
+ * 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)
+
+struct sr6_tlv {
+ __u8 type;
+ __u8 len;
+ __u8 data[0];
+};
+
+#endif
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 060dd99..2ac6cb4 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)
@@ -6036,6 +6039,13 @@ 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..b8ba396 100644
--- a/net/ipv6/exthdrs.c
+++ b/net/ipv6/exthdrs.c
@@ -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) {
--
2.7.3
