ipv6: sr: add helper functions for seg6local

This patch adds three helper functions to be used with the seg6local packet
processing actions.

The decap_and_validate() function will be used by the End.D* actions, that
decapsulate an SR-enabled packet.

The advance_nextseg() function applies the fundamental operations to update
an SRH for the next segment.

The lookup_nexthop() function helps select the next-hop for the processed
SR packets. It supports an optional next-hop address to route the packet
specifically through it, and an optional routing table to use.

Signed-off-by: David Lebrun <david.lebrun@uclouvain.be>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv6/Kconfig b/net/ipv6/Kconfig
index 0d722396dce65f1dbc691d51cea3be9160dc06b2..ea71e4b0ab7aea80fc6b564fddeea7a6b01feaeb 100644 (file)
--- a/net/ipv6/Kconfig
+++ b/net/ipv6/Kconfig
@@ -308,6 +308,7 @@ config IPV6_SEG6_LWTUNNEL
        depends on IPV6
        select LWTUNNEL
        select DST_CACHE
+       select IPV6_MULTIPLE_TABLES
        ---help---
          Support for encapsulation of packets within an outer IPv6
          header and a Segment Routing Header using the lightweight

diff --git a/net/ipv6/seg6_local.c b/net/ipv6/seg6_local.c
index c6263256fcf640b4a61ec80f831d64bac94645a3..26db4d3e875544579617026f59c53f417115bc69 100644 (file)
--- a/net/ipv6/seg6_local.c
+++ b/net/ipv6/seg6_local.c
@@ -99,23 +99,105 @@ static struct ipv6_sr_hdr *get_and_validate_srh(struct sk_buff *skb)
        return srh;
 }
 
+static bool decap_and_validate(struct sk_buff *skb, int proto)
+{
+       struct ipv6_sr_hdr *srh;
+       unsigned int off = 0;
+
+       srh = get_srh(skb);
+       if (srh && srh->segments_left > 0)
+               return false;
+
+#ifdef CONFIG_IPV6_SEG6_HMAC
+       if (srh && !seg6_hmac_validate_skb(skb))
+               return false;
+#endif
+
+       if (ipv6_find_hdr(skb, &off, proto, NULL, NULL) < 0)
+               return false;
+
+       if (!pskb_pull(skb, off))
+               return false;
+
+       skb_postpull_rcsum(skb, skb_network_header(skb), off);
+
+       skb_reset_network_header(skb);
+       skb_reset_transport_header(skb);
+       skb->encapsulation = 0;
+
+       return true;
+}
+
+static void advance_nextseg(struct ipv6_sr_hdr *srh, struct in6_addr *daddr)
+{
+       struct in6_addr *addr;
+
+       srh->segments_left--;
+       addr = srh->segments + srh->segments_left;
+       *daddr = *addr;
+}
+
+static void lookup_nexthop(struct sk_buff *skb, struct in6_addr *nhaddr,
+                          u32 tbl_id)
+{
+       struct net *net = dev_net(skb->dev);
+       struct ipv6hdr *hdr = ipv6_hdr(skb);
+       int flags = RT6_LOOKUP_F_HAS_SADDR;
+       struct dst_entry *dst = NULL;
+       struct rt6_info *rt;
+       struct flowi6 fl6;
+
+       fl6.flowi6_iif = skb->dev->ifindex;
+       fl6.daddr = nhaddr ? *nhaddr : hdr->daddr;
+       fl6.saddr = hdr->saddr;
+       fl6.flowlabel = ip6_flowinfo(hdr);
+       fl6.flowi6_mark = skb->mark;
+       fl6.flowi6_proto = hdr->nexthdr;
+
+       if (nhaddr)
+               fl6.flowi6_flags = FLOWI_FLAG_KNOWN_NH;
+
+       if (!tbl_id) {
+               dst = ip6_route_input_lookup(net, skb->dev, &fl6, flags);
+       } else {
+               struct fib6_table *table;
+
+               table = fib6_get_table(net, tbl_id);
+               if (!table)
+                       goto out;
+
+               rt = ip6_pol_route(net, table, 0, &fl6, flags);
+               dst = &rt->dst;
+       }
+
+       if (dst && dst->dev->flags & IFF_LOOPBACK && !dst->error) {
+               dst_release(dst);
+               dst = NULL;
+       }
+
+out:
+       if (!dst) {
+               rt = net->ipv6.ip6_blk_hole_entry;
+               dst = &rt->dst;
+               dst_hold(dst);
+       }
+
+       skb_dst_drop(skb);
+       skb_dst_set(skb, dst);
+}
+
 /* regular endpoint function */
 static int input_action_end(struct sk_buff *skb, struct seg6_local_lwt *slwt)
 {
        struct ipv6_sr_hdr *srh;
-       struct in6_addr *addr;
 
        srh = get_and_validate_srh(skb);
        if (!srh)
                goto drop;
 
-       srh->segments_left--;
-       addr = srh->segments + srh->segments_left;
-
-       ipv6_hdr(skb)->daddr = *addr;
+       advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
 
-       skb_dst_drop(skb);
-       ip6_route_input(skb);
+       lookup_nexthop(skb, NULL, 0);
 
        return dst_input(skb);
 
@@ -127,41 +209,15 @@ drop:
 /* regular endpoint, and forward to specified nexthop */
 static int input_action_end_x(struct sk_buff *skb, struct seg6_local_lwt *slwt)
 {
-       struct net *net = dev_net(skb->dev);
        struct ipv6_sr_hdr *srh;
-       struct dst_entry *dst;
-       struct in6_addr *addr;
-       struct ipv6hdr *hdr;
-       struct flowi6 fl6;
-       int flags;
 
        srh = get_and_validate_srh(skb);
        if (!srh)
                goto drop;
 
-       srh->segments_left--;
-       addr = srh->segments + srh->segments_left;
-
-       hdr = ipv6_hdr(skb);
-       hdr->daddr = *addr;
-
-       skb_dst_drop(skb);
-
-       fl6.flowi6_iif = skb->dev->ifindex;
-       fl6.daddr = slwt->nh6;
-       fl6.saddr = hdr->saddr;
-       fl6.flowlabel = ip6_flowinfo(hdr);
-       fl6.flowi6_mark = skb->mark;
-       fl6.flowi6_proto = hdr->nexthdr;
-
-       flags = RT6_LOOKUP_F_HAS_SADDR | RT6_LOOKUP_F_IFACE |
-               RT6_LOOKUP_F_REACHABLE;
+       advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
 
-       dst = ip6_route_input_lookup(net, skb->dev, &fl6, flags);
-       if (dst->dev->flags & IFF_LOOPBACK)
-               goto drop;
-
-       skb_dst_set(skb, dst);
+       lookup_nexthop(skb, &slwt->nh6, 0);
 
        return dst_input(skb);
 
@@ -174,42 +230,18 @@ drop:
 static int input_action_end_dx6(struct sk_buff *skb,
                                struct seg6_local_lwt *slwt)
 {
-       struct net *net = dev_net(skb->dev);
-       struct ipv6hdr *inner_hdr;
-       struct ipv6_sr_hdr *srh;
-       struct dst_entry *dst;
-       unsigned int off = 0;
-       struct flowi6 fl6;
-       bool use_nh;
-       int flags;
+       struct in6_addr *nhaddr = NULL;
 
        /* this function accepts IPv6 encapsulated packets, with either
         * an SRH with SL=0, or no SRH.
         */
 
-       srh = get_srh(skb);
-       if (srh && srh->segments_left > 0)
-               goto drop;
-
-#ifdef CONFIG_IPV6_SEG6_HMAC
-       if (srh && !seg6_hmac_validate_skb(skb))
+       if (!decap_and_validate(skb, IPPROTO_IPV6))
                goto drop;
-#endif
 
-       if (ipv6_find_hdr(skb, &off, IPPROTO_IPV6, NULL, NULL) < 0)
-               goto drop;
-
-       if (!pskb_pull(skb, off))
+       if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
                goto drop;
 
-       skb_postpull_rcsum(skb, skb_network_header(skb), off);
-
-       skb_reset_network_header(skb);
-       skb_reset_transport_header(skb);
-       skb->encapsulation = 0;
-
-       inner_hdr = ipv6_hdr(skb);
-
        /* The inner packet is not associated to any local interface,
         * so we do not call netif_rx().
         *
@@ -217,26 +249,10 @@ static int input_action_end_dx6(struct sk_buff *skb,
         * inner packet's DA. Otherwise, use the specified nexthop.
         */
 
-       use_nh = !ipv6_addr_any(&slwt->nh6);
+       if (!ipv6_addr_any(&slwt->nh6))
+               nhaddr = &slwt->nh6;
 
-       skb_dst_drop(skb);
-
-       fl6.flowi6_iif = skb->dev->ifindex;
-       fl6.daddr = use_nh ? slwt->nh6 : inner_hdr->daddr;
-       fl6.saddr = inner_hdr->saddr;
-       fl6.flowlabel = ip6_flowinfo(inner_hdr);
-       fl6.flowi6_mark = skb->mark;
-       fl6.flowi6_proto = inner_hdr->nexthdr;
-
-       flags = RT6_LOOKUP_F_HAS_SADDR | RT6_LOOKUP_F_REACHABLE;
-       if (use_nh)
-               flags |= RT6_LOOKUP_F_IFACE;
-
-       dst = ip6_route_input_lookup(net, skb->dev, &fl6, flags);
-       if (dst->dev->flags & IFF_LOOPBACK)
-               goto drop;
-
-       skb_dst_set(skb, dst);
+       lookup_nexthop(skb, nhaddr, 0);
 
        return dst_input(skb);
 drop:
@@ -261,8 +277,7 @@ static int input_action_end_b6(struct sk_buff *skb, struct seg6_local_lwt *slwt)
        ipv6_hdr(skb)->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
        skb_set_transport_header(skb, sizeof(struct ipv6hdr));
 
-       skb_dst_drop(skb);
-       ip6_route_input(skb);
+       lookup_nexthop(skb, NULL, 0);
 
        return dst_input(skb);
 
@@ -276,16 +291,13 @@ static int input_action_end_b6_encap(struct sk_buff *skb,
                                     struct seg6_local_lwt *slwt)
 {
        struct ipv6_sr_hdr *srh;
-       struct in6_addr *addr;
        int err = -EINVAL;
 
        srh = get_and_validate_srh(skb);
        if (!srh)
                goto drop;
 
-       srh->segments_left--;
-       addr = srh->segments + srh->segments_left;
-       ipv6_hdr(skb)->daddr = *addr;
+       advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
 
        skb_reset_inner_headers(skb);
        skb->encapsulation = 1;
@@ -297,8 +309,7 @@ static int input_action_end_b6_encap(struct sk_buff *skb,
        ipv6_hdr(skb)->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
        skb_set_transport_header(skb, sizeof(struct ipv6hdr));
 
-       skb_dst_drop(skb);
-       ip6_route_input(skb);
+       lookup_nexthop(skb, NULL, 0);
 
        return dst_input(skb);