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author | Ed Swierk <eswierk@skyportsystems.com> | 2018-01-31 18:48:02 -0800 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2018-02-01 09:46:22 -0500 |
commit | 9382fe71c0058465e942a633869629929102843d (patch) | |
tree | a67c6d0859748ef1a443189f08113e2b855a691b /net/openvswitch | |
parent | 3aff3b4b986e51bcf4ab249e5d48d39596e0df6a (diff) | |
download | talos-op-linux-9382fe71c0058465e942a633869629929102843d.tar.gz talos-op-linux-9382fe71c0058465e942a633869629929102843d.zip |
openvswitch: Remove padding from packet before L3+ conntrack processing
IPv4 and IPv6 packets may arrive with lower-layer padding that is not
included in the L3 length. For example, a short IPv4 packet may have
up to 6 bytes of padding following the IP payload when received on an
Ethernet device with a minimum packet length of 64 bytes.
Higher-layer processing functions in netfilter (e.g. nf_ip_checksum(),
and help() in nf_conntrack_ftp) assume skb->len reflects the length of
the L3 header and payload, rather than referring back to
ip_hdr->tot_len or ipv6_hdr->payload_len, and get confused by
lower-layer padding.
In the normal IPv4 receive path, ip_rcv() trims the packet to
ip_hdr->tot_len before invoking netfilter hooks. In the IPv6 receive
path, ip6_rcv() does the same using ipv6_hdr->payload_len. Similarly
in the br_netfilter receive path, br_validate_ipv4() and
br_validate_ipv6() trim the packet to the L3 length before invoking
netfilter hooks.
Currently in the OVS conntrack receive path, ovs_ct_execute() pulls
the skb to the L3 header but does not trim it to the L3 length before
calling nf_conntrack_in(NF_INET_PRE_ROUTING). When
nf_conntrack_proto_tcp encounters a packet with lower-layer padding,
nf_ip_checksum() fails causing a "nf_ct_tcp: bad TCP checksum" log
message. While extra zero bytes don't affect the checksum, the length
in the IP pseudoheader does. That length is based on skb->len, and
without trimming, it doesn't match the length the sender used when
computing the checksum.
In ovs_ct_execute(), trim the skb to the L3 length before higher-layer
processing.
Signed-off-by: Ed Swierk <eswierk@skyportsystems.com>
Acked-by: Pravin B Shelar <pshelar@ovn.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/openvswitch')
-rw-r--r-- | net/openvswitch/conntrack.c | 34 |
1 files changed, 34 insertions, 0 deletions
diff --git a/net/openvswitch/conntrack.c b/net/openvswitch/conntrack.c index 62f36cc938ca..c5904f629091 100644 --- a/net/openvswitch/conntrack.c +++ b/net/openvswitch/conntrack.c @@ -1098,6 +1098,36 @@ static int ovs_ct_commit(struct net *net, struct sw_flow_key *key, return 0; } +/* Trim the skb to the length specified by the IP/IPv6 header, + * removing any trailing lower-layer padding. This prepares the skb + * for higher-layer processing that assumes skb->len excludes padding + * (such as nf_ip_checksum). The caller needs to pull the skb to the + * network header, and ensure ip_hdr/ipv6_hdr points to valid data. + */ +static int ovs_skb_network_trim(struct sk_buff *skb) +{ + unsigned int len; + int err; + + switch (skb->protocol) { + case htons(ETH_P_IP): + len = ntohs(ip_hdr(skb)->tot_len); + break; + case htons(ETH_P_IPV6): + len = sizeof(struct ipv6hdr) + + ntohs(ipv6_hdr(skb)->payload_len); + break; + default: + len = skb->len; + } + + err = pskb_trim_rcsum(skb, len); + if (err) + kfree_skb(skb); + + return err; +} + /* Returns 0 on success, -EINPROGRESS if 'skb' is stolen, or other nonzero * value if 'skb' is freed. */ @@ -1112,6 +1142,10 @@ int ovs_ct_execute(struct net *net, struct sk_buff *skb, nh_ofs = skb_network_offset(skb); skb_pull_rcsum(skb, nh_ofs); + err = ovs_skb_network_trim(skb); + if (err) + return err; + if (key->ip.frag != OVS_FRAG_TYPE_NONE) { err = handle_fragments(net, key, info->zone.id, skb); if (err) |