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Message-Id: <20160614215302.21641-1-philipp@redfish-solutions.com>
Date: Tue, 14 Jun 2016 15:53:02 -0600
From: "Philip Prindeville" <philipp@...fish-solutions.com>
To: netdev@...r.kernel.org
Cc: Stephen Hemminger <stephen@...workplumber.org>,
Alexander Duyck <alexander.duyck@...il.com>,
Philip Prindeville <philipp@...fish-solutions.com>
Subject: [PATCH v2 net-next] net: ipv4: Add ability to have GRE ignore DF bit in IPv4 payloads
From: Philip Prindeville <philipp@...fish-solutions.com>
In the presence of firewalls which improperly block ICMP Unreachable
(including Fragmentation Required) messages, Path MTU Discovery is
prevented from working.
A workaround is to handle IPv4 payloads opaquely, ignoring the DF bit--as
is done for other payloads like AppleTalk--and doing transparent
fragmentation and reassembly.
Redux includes the enforcement of mutual exclusion between this feature
and Path MTU Discovery as suggested by Alexander Duyck.
Cc: Alexander Duyck <alexander.duyck@...il.com>
Reviewed-by: Stephen Hemminger <stephen@...workplumber.org>
Signed-off-by: Philip Prindeville <philipp@...fish-solutions.com>
---
include/net/ip_tunnels.h | 1 +
include/uapi/linux/if_tunnel.h | 1 +
net/ipv4/ip_gre.c | 42 +++++++++++++++++++++++++++++++++---------
net/ipv4/ip_tunnel.c | 2 +-
4 files changed, 36 insertions(+), 10 deletions(-)
diff --git a/include/net/ip_tunnels.h b/include/net/ip_tunnels.h
index dbf4444..9222678 100644
--- a/include/net/ip_tunnels.h
+++ b/include/net/ip_tunnels.h
@@ -132,6 +132,7 @@ struct ip_tunnel {
int ip_tnl_net_id;
struct gro_cells gro_cells;
bool collect_md;
+ bool ignore_df;
};
#define TUNNEL_CSUM __cpu_to_be16(0x01)
diff --git a/include/uapi/linux/if_tunnel.h b/include/uapi/linux/if_tunnel.h
index af4de90..1046f55 100644
--- a/include/uapi/linux/if_tunnel.h
+++ b/include/uapi/linux/if_tunnel.h
@@ -113,6 +113,7 @@ enum {
IFLA_GRE_ENCAP_SPORT,
IFLA_GRE_ENCAP_DPORT,
IFLA_GRE_COLLECT_METADATA,
+ IFLA_GRE_IGNORE_DF,
__IFLA_GRE_MAX,
};
diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index 4d2025f..0f8ca3f 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -841,17 +841,19 @@ out:
return ipgre_tunnel_validate(tb, data);
}
-static void ipgre_netlink_parms(struct net_device *dev,
+static int ipgre_netlink_parms(struct net_device *dev,
struct nlattr *data[],
struct nlattr *tb[],
struct ip_tunnel_parm *parms)
{
+ struct ip_tunnel *t = netdev_priv(dev);
+
memset(parms, 0, sizeof(*parms));
parms->iph.protocol = IPPROTO_GRE;
if (!data)
- return;
+ return 0;
if (data[IFLA_GRE_LINK])
parms->link = nla_get_u32(data[IFLA_GRE_LINK]);
@@ -880,16 +882,26 @@ static void ipgre_netlink_parms(struct net_device *dev,
if (data[IFLA_GRE_TOS])
parms->iph.tos = nla_get_u8(data[IFLA_GRE_TOS]);
- if (!data[IFLA_GRE_PMTUDISC] || nla_get_u8(data[IFLA_GRE_PMTUDISC]))
+ if (!data[IFLA_GRE_PMTUDISC] || nla_get_u8(data[IFLA_GRE_PMTUDISC])) {
+ if (t->ignore_df)
+ return -EINVAL;
parms->iph.frag_off = htons(IP_DF);
+ }
if (data[IFLA_GRE_COLLECT_METADATA]) {
- struct ip_tunnel *t = netdev_priv(dev);
-
t->collect_md = true;
if (dev->type == ARPHRD_IPGRE)
dev->type = ARPHRD_NONE;
}
+
+ if (data[IFLA_GRE_IGNORE_DF]) {
+ if (nla_get_u8(data[IFLA_GRE_IGNORE_DF])
+ && (parms->iph.frag_off & htons(IP_DF)))
+ return -EINVAL;
+ t->ignore_df = !!nla_get_u8(data[IFLA_GRE_IGNORE_DF]);
+ }
+
+ return 0;
}
/* This function returns true when ENCAP attributes are present in the nl msg */
@@ -960,16 +972,19 @@ static int ipgre_newlink(struct net *src_net, struct net_device *dev,
{
struct ip_tunnel_parm p;
struct ip_tunnel_encap ipencap;
+ int err;
if (ipgre_netlink_encap_parms(data, &ipencap)) {
struct ip_tunnel *t = netdev_priv(dev);
- int err = ip_tunnel_encap_setup(t, &ipencap);
+ err = ip_tunnel_encap_setup(t, &ipencap);
if (err < 0)
return err;
}
- ipgre_netlink_parms(dev, data, tb, &p);
+ err = ipgre_netlink_parms(dev, data, tb, &p);
+ if (err < 0)
+ return err;
return ip_tunnel_newlink(dev, tb, &p);
}
@@ -978,16 +993,19 @@ static int ipgre_changelink(struct net_device *dev, struct nlattr *tb[],
{
struct ip_tunnel_parm p;
struct ip_tunnel_encap ipencap;
+ int err;
if (ipgre_netlink_encap_parms(data, &ipencap)) {
struct ip_tunnel *t = netdev_priv(dev);
- int err = ip_tunnel_encap_setup(t, &ipencap);
+ err = ip_tunnel_encap_setup(t, &ipencap);
if (err < 0)
return err;
}
- ipgre_netlink_parms(dev, data, tb, &p);
+ err = ipgre_netlink_parms(dev, data, tb, &p);
+ if (err < 0)
+ return err;
return ip_tunnel_changelink(dev, tb, &p);
}
@@ -1024,6 +1042,8 @@ static size_t ipgre_get_size(const struct net_device *dev)
nla_total_size(2) +
/* IFLA_GRE_COLLECT_METADATA */
nla_total_size(0) +
+ /* IFLA_GRE_IGNORE_DF */
+ nla_total_size(1) +
0;
}
@@ -1057,6 +1077,9 @@ static int ipgre_fill_info(struct sk_buff *skb, const struct net_device *dev)
t->encap.flags))
goto nla_put_failure;
+ if (nla_put_u8(skb, IFLA_GRE_IGNORE_DF, t->ignore_df))
+ goto nla_put_failure;
+
if (t->collect_md) {
if (nla_put_flag(skb, IFLA_GRE_COLLECT_METADATA))
goto nla_put_failure;
@@ -1084,6 +1107,7 @@ static const struct nla_policy ipgre_policy[IFLA_GRE_MAX + 1] = {
[IFLA_GRE_ENCAP_SPORT] = { .type = NLA_U16 },
[IFLA_GRE_ENCAP_DPORT] = { .type = NLA_U16 },
[IFLA_GRE_COLLECT_METADATA] = { .type = NLA_FLAG },
+ [IFLA_GRE_IGNORE_DF] = { .type = NLA_U8 },
};
static struct rtnl_link_ops ipgre_link_ops __read_mostly = {
diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index d8f5e0a..95649eb 100644
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -682,7 +682,7 @@ void ip_tunnel_xmit(struct sk_buff *skb, struct net_device *dev,
}
df = tnl_params->frag_off;
- if (skb->protocol == htons(ETH_P_IP))
+ if (skb->protocol == htons(ETH_P_IP) && !tunnel->ignore_df)
df |= (inner_iph->frag_off&htons(IP_DF));
max_headroom = LL_RESERVED_SPACE(rt->dst.dev) + sizeof(struct iphdr)
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