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    Subject[PATCH 3.16.y-ckt 084/170] drivers/net, ipv6: Select IPv6 fragment idents for virtio UFO packets
    Date
    3.16.7-ckt1 -stable 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>
    Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
    ---
    drivers/net/macvtap.c | 3 +++
    drivers/net/tun.c | 6 +++++-
    include/net/ipv6.h | 2 ++
    net/ipv6/output_core.c | 34 ++++++++++++++++++++++++++++++++++
    4 files changed, 44 insertions(+), 1 deletion(-)

    diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
    index 1f8ca1e4c46c..f30ceb17d5fc 100644
    --- a/drivers/net/macvtap.c
    +++ b/drivers/net/macvtap.c
    @@ -16,6 +16,7 @@
    #include <linux/idr.h>
    #include <linux/fs.h>

    +#include <net/ipv6.h>
    #include <net/net_namespace.h>
    #include <net/rtnetlink.h>
    #include <net/sock.h>
    @@ -572,6 +573,8 @@ static int macvtap_skb_from_vnet_hdr(struct sk_buff *skb,
    pr_warn_once("macvtap: %s: using disabled UFO feature; please fix this program\n",
    current->comm);
    gso_type = SKB_GSO_UDP;
    + if (skb->protocol == htons(ETH_P_IPV6))
    + ipv6_proxy_select_ident(skb);
    break;
    default:
    return -EINVAL;
    diff --git a/drivers/net/tun.c b/drivers/net/tun.c
    index 5716e63d5be1..9ec6c8b5bf99 100644
    --- a/drivers/net/tun.c
    +++ b/drivers/net/tun.c
    @@ -65,6 +65,7 @@
    #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>
    @@ -1139,6 +1140,8 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
    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) {
    @@ -1159,6 +1162,8 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
    current->comm);
    }
    skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
    + if (skb->protocol == htons(ETH_P_IPV6))
    + ipv6_proxy_select_ident(skb);
    break;
    }
    default:
    @@ -1189,7 +1194,6 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
    skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;
    }

    - skb_reset_network_header(skb);
    skb_probe_transport_header(skb, 0);

    rxhash = skb_get_hash(skb);
    diff --git a/include/net/ipv6.h b/include/net/ipv6.h
    index 574337fe72dd..9b442a8d68ba 100644
    --- a/include/net/ipv6.h
    +++ b/include/net/ipv6.h
    @@ -668,6 +668,8 @@ static inline int ipv6_addr_diff(const struct in6_addr *a1, const struct in6_add
    return __ipv6_addr_diff(a1, a2, sizeof(struct in6_addr));
    }

    +void ipv6_proxy_select_ident(struct sk_buff *skb);
    +
    int ip6_dst_hoplimit(struct dst_entry *dst);

    static inline int ip6_sk_dst_hoplimit(struct ipv6_pinfo *np, struct flowi6 *fl6,
    diff --git a/net/ipv6/output_core.c b/net/ipv6/output_core.c
    index 5ec867e4a8b7..1d4156ddf355 100644
    --- a/net/ipv6/output_core.c
    +++ b/net/ipv6/output_core.c
    @@ -3,11 +3,45 @@
    * not configured or static. These functions are needed by GSO/GRO implementation.
    */
    #include <linux/export.h>
    +#include <net/ip.h>
    #include <net/ipv6.h>
    #include <net/ip6_fib.h>
    #include <net/addrconf.h>
    #include <net/secure_seq.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.
    + *
    + * The network header must be set before calling this.
    + */
    +void ipv6_proxy_select_ident(struct sk_buff *skb)
    +{
    + static u32 ip6_proxy_idents_hashrnd __read_mostly;
    + 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;
    +
    + net_get_random_once(&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);
    +
    int ip6_find_1stfragopt(struct sk_buff *skb, u8 **nexthdr)
    {
    u16 offset = sizeof(struct ipv6hdr);
    --
    2.1.0


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