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Subject[PATCH 3.2 19/27] drivers/net, ipv6: Select IPv6 fragment idents for virtio UFO packets
3.2.66-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Ben Hutchings <ben@decadent.org.uk>

commit 5188cd44c55db3e92cd9e77a40b5baa7ed4340f7 upstream.

UFO is now disabled on all drivers that work with virtio net headers,
but userland may try to send UFO/IPv6 packets anyway. Instead of
sending with ID=0, we should select identifiers on their behalf (as we
used to).

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Fixes: 916e4cf46d02 ("ipv6: reuse ip6_frag_id from ip6_ufo_append_data")
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: For 3.2, net/ipv6/output_core.c is a completely new file]
---
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -15,6 +15,7 @@
#include <linux/cdev.h>
#include <linux/fs.h>

+#include <net/ipv6.h>
#include <net/net_namespace.h>
#include <net/rtnetlink.h>
#include <net/sock.h>
@@ -577,6 +578,8 @@ static int macvtap_skb_from_vnet_hdr(str
break;
case VIRTIO_NET_HDR_GSO_UDP:
gso_type = SKB_GSO_UDP;
+ if (skb->protocol == htons(ETH_P_IPV6))
+ ipv6_proxy_select_ident(skb);
break;
default:
return -EINVAL;
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -64,6 +64,7 @@
#include <linux/nsproxy.h>
#include <linux/virtio_net.h>
#include <linux/rcupdate.h>
+#include <net/ipv6.h>
#include <net/net_namespace.h>
#include <net/netns/generic.h>
#include <net/rtnetlink.h>
@@ -695,6 +696,8 @@ static ssize_t tun_get_user(struct tun_s
break;
}

+ skb_reset_network_header(skb);
+
if (gso.gso_type != VIRTIO_NET_HDR_GSO_NONE) {
pr_debug("GSO!\n");
switch (gso.gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {
@@ -706,6 +709,8 @@ static ssize_t tun_get_user(struct tun_s
break;
case VIRTIO_NET_HDR_GSO_UDP:
skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
+ if (skb->protocol == htons(ETH_P_IPV6))
+ ipv6_proxy_select_ident(skb);
break;
default:
tun->dev->stats.rx_frame_errors++;
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -481,6 +481,7 @@ static inline int ipv6_addr_diff(const s
}

extern void ipv6_select_ident(struct frag_hdr *fhdr, struct rt6_info *rt);
+void ipv6_proxy_select_ident(struct sk_buff *skb);

/*
* Prototypes exported by ipv6
--- /dev/null
+++ b/net/ipv6/output_core.c
@@ -0,0 +1,38 @@
+#include <linux/export.h>
+#include <linux/skbuff.h>
+#include <net/ip.h>
+#include <net/ipv6.h>
+
+/* This function exists only for tap drivers that must support broken
+ * clients requesting UFO without specifying an IPv6 fragment ID.
+ *
+ * This is similar to ipv6_select_ident() but we use an independent hash
+ * seed to limit information leakage.
+ */
+void ipv6_proxy_select_ident(struct sk_buff *skb)
+{
+ static u32 ip6_proxy_idents_hashrnd __read_mostly;
+ static bool hashrnd_initialized = false;
+ struct in6_addr buf[2];
+ struct in6_addr *addrs;
+ u32 hash, id;
+
+ addrs = skb_header_pointer(skb,
+ skb_network_offset(skb) +
+ offsetof(struct ipv6hdr, saddr),
+ sizeof(buf), buf);
+ if (!addrs)
+ return;
+
+ if (unlikely(!hashrnd_initialized)) {
+ hashrnd_initialized = true;
+ get_random_bytes(&ip6_proxy_idents_hashrnd,
+ sizeof(ip6_proxy_idents_hashrnd));
+ }
+ hash = __ipv6_addr_jhash(&addrs[1], ip6_proxy_idents_hashrnd);
+ hash = __ipv6_addr_jhash(&addrs[0], hash);
+
+ id = ip_idents_reserve(hash, 1);
+ skb_shinfo(skb)->ip6_frag_id = htonl(id);
+}
+EXPORT_SYMBOL_GPL(ipv6_proxy_select_ident);
--- a/net/ipv6/Makefile
+++ b/net/ipv6/Makefile
@@ -37,6 +37,6 @@ obj-$(CONFIG_NETFILTER) += netfilter/
obj-$(CONFIG_IPV6_SIT) += sit.o
obj-$(CONFIG_IPV6_TUNNEL) += ip6_tunnel.o

-obj-y += addrconf_core.o exthdrs_core.o
+obj-y += addrconf_core.o exthdrs_core.o output_core.o

obj-$(subst m,y,$(CONFIG_IPV6)) += inet6_hashtables.o


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