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Merge branch 'ip6_gre-Fixes-in-headroom-handling'
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Petr Machata says:

====================
net: ip6_gre: Fixes in headroom handling

This series mends some problems in headroom management in ip6_gre
module. The current code base has the following three closely-related
problems:

- ip6gretap tunnels neglect to ensure there's enough writable headroom
  before pushing GRE headers.

- ip6erspan does this, but assumes that dev->needed_headroom is primed.
  But that doesn't happen until ip6_tnl_xmit() is called later. Thus for
  the first packet, ip6erspan actually behaves like ip6gretap above.

- ip6erspan shares some of the code with ip6gretap, including
  calculations of needed header length. While there is custom
  ERSPAN-specific code for calculating the headroom, the computed
  values are overwritten by the ip6gretap code.

The first two issues lead to a kernel panic in situations where a packet
is mirrored from a veth device to the device in question. They are
fixed, respectively, in patches #1 and #2, which include the full panic
trace and a reproducer.

The rest of the patchset deals with the last issue. In patches #3 to #6,
several functions are split up into reusable parts. Finally in patch #7
these blocks are used to compose ERSPAN-specific callbacks where
necessary to fix the hlen calculation.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
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@davem330
davem330 committed May 17, 2018
2 parents 02f99df + 2d66503 commit 374edea
Showing 1 changed file with 145 additions and 39 deletions.
184 changes: 145 additions & 39 deletions net/ipv6/ip6_gre.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -81,6 +81,7 @@ static int ip6gre_tunnel_init(struct net_device *dev);
static void ip6gre_tunnel_setup(struct net_device *dev);
static void ip6gre_tunnel_link(struct ip6gre_net *ign, struct ip6_tnl *t);
static void ip6gre_tnl_link_config(struct ip6_tnl *t, int set_mtu);
static void ip6erspan_tnl_link_config(struct ip6_tnl *t, int set_mtu);

/* Tunnel hash table */

Expand Down Expand Up @@ -698,6 +699,9 @@ static netdev_tx_t __gre6_xmit(struct sk_buff *skb,
else
fl6->daddr = tunnel->parms.raddr;

if (skb_cow_head(skb, dev->needed_headroom ?: tunnel->hlen))
return -ENOMEM;

/* Push GRE header. */
protocol = (dev->type == ARPHRD_ETHER) ? htons(ETH_P_TEB) : proto;

Expand Down Expand Up @@ -908,7 +912,7 @@ static netdev_tx_t ip6erspan_tunnel_xmit(struct sk_buff *skb,
truncate = true;
}

if (skb_cow_head(skb, dev->needed_headroom))
if (skb_cow_head(skb, dev->needed_headroom ?: t->hlen))
goto tx_err;

t->parms.o_flags &= ~TUNNEL_KEY;
Expand Down Expand Up @@ -1022,12 +1026,11 @@ static netdev_tx_t ip6erspan_tunnel_xmit(struct sk_buff *skb,
return NETDEV_TX_OK;
}

static void ip6gre_tnl_link_config(struct ip6_tnl *t, int set_mtu)
static void ip6gre_tnl_link_config_common(struct ip6_tnl *t)
{
struct net_device *dev = t->dev;
struct __ip6_tnl_parm *p = &t->parms;
struct flowi6 *fl6 = &t->fl.u.ip6;
int t_hlen;

if (dev->type != ARPHRD_ETHER) {
memcpy(dev->dev_addr, &p->laddr, sizeof(struct in6_addr));
Expand All @@ -1054,12 +1057,13 @@ static void ip6gre_tnl_link_config(struct ip6_tnl *t, int set_mtu)
dev->flags |= IFF_POINTOPOINT;
else
dev->flags &= ~IFF_POINTOPOINT;
}

t->tun_hlen = gre_calc_hlen(t->parms.o_flags);

t->hlen = t->encap_hlen + t->tun_hlen;

t_hlen = t->hlen + sizeof(struct ipv6hdr);
static void ip6gre_tnl_link_config_route(struct ip6_tnl *t, int set_mtu,
int t_hlen)
{
const struct __ip6_tnl_parm *p = &t->parms;
struct net_device *dev = t->dev;

if (p->flags & IP6_TNL_F_CAP_XMIT) {
int strict = (ipv6_addr_type(&p->raddr) &
Expand Down Expand Up @@ -1091,8 +1095,26 @@ static void ip6gre_tnl_link_config(struct ip6_tnl *t, int set_mtu)
}
}

static int ip6gre_tnl_change(struct ip6_tnl *t,
const struct __ip6_tnl_parm *p, int set_mtu)
static int ip6gre_calc_hlen(struct ip6_tnl *tunnel)
{
int t_hlen;

tunnel->tun_hlen = gre_calc_hlen(tunnel->parms.o_flags);
tunnel->hlen = tunnel->tun_hlen + tunnel->encap_hlen;

t_hlen = tunnel->hlen + sizeof(struct ipv6hdr);
tunnel->dev->hard_header_len = LL_MAX_HEADER + t_hlen;
return t_hlen;
}

static void ip6gre_tnl_link_config(struct ip6_tnl *t, int set_mtu)
{
ip6gre_tnl_link_config_common(t);
ip6gre_tnl_link_config_route(t, set_mtu, ip6gre_calc_hlen(t));
}

static void ip6gre_tnl_copy_tnl_parm(struct ip6_tnl *t,
const struct __ip6_tnl_parm *p)
{
t->parms.laddr = p->laddr;
t->parms.raddr = p->raddr;
Expand All @@ -1108,6 +1130,12 @@ static int ip6gre_tnl_change(struct ip6_tnl *t,
t->parms.o_flags = p->o_flags;
t->parms.fwmark = p->fwmark;
dst_cache_reset(&t->dst_cache);
}

static int ip6gre_tnl_change(struct ip6_tnl *t, const struct __ip6_tnl_parm *p,
int set_mtu)
{
ip6gre_tnl_copy_tnl_parm(t, p);
ip6gre_tnl_link_config(t, set_mtu);
return 0;
}
Expand Down Expand Up @@ -1384,11 +1412,7 @@ static int ip6gre_tunnel_init_common(struct net_device *dev)
return ret;
}

tunnel->tun_hlen = gre_calc_hlen(tunnel->parms.o_flags);
tunnel->hlen = tunnel->tun_hlen + tunnel->encap_hlen;
t_hlen = tunnel->hlen + sizeof(struct ipv6hdr);

dev->hard_header_len = LL_MAX_HEADER + t_hlen;
t_hlen = ip6gre_calc_hlen(tunnel);
dev->mtu = ETH_DATA_LEN - t_hlen;
if (dev->type == ARPHRD_ETHER)
dev->mtu -= ETH_HLEN;
Expand Down Expand Up @@ -1731,6 +1755,19 @@ static const struct net_device_ops ip6gre_tap_netdev_ops = {
.ndo_get_iflink = ip6_tnl_get_iflink,
};

static int ip6erspan_calc_hlen(struct ip6_tnl *tunnel)
{
int t_hlen;

tunnel->tun_hlen = 8;
tunnel->hlen = tunnel->tun_hlen + tunnel->encap_hlen +
erspan_hdr_len(tunnel->parms.erspan_ver);

t_hlen = tunnel->hlen + sizeof(struct ipv6hdr);
tunnel->dev->hard_header_len = LL_MAX_HEADER + t_hlen;
return t_hlen;
}

static int ip6erspan_tap_init(struct net_device *dev)
{
struct ip6_tnl *tunnel;
Expand All @@ -1754,20 +1791,15 @@ static int ip6erspan_tap_init(struct net_device *dev)
return ret;
}

tunnel->tun_hlen = 8;
tunnel->hlen = tunnel->tun_hlen + tunnel->encap_hlen +
erspan_hdr_len(tunnel->parms.erspan_ver);
t_hlen = tunnel->hlen + sizeof(struct ipv6hdr);

dev->hard_header_len = LL_MAX_HEADER + t_hlen;
t_hlen = ip6erspan_calc_hlen(tunnel);
dev->mtu = ETH_DATA_LEN - t_hlen;
if (dev->type == ARPHRD_ETHER)
dev->mtu -= ETH_HLEN;
if (!(tunnel->parms.flags & IP6_TNL_F_IGN_ENCAP_LIMIT))
dev->mtu -= 8;

dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
ip6gre_tnl_link_config(tunnel, 1);
ip6erspan_tnl_link_config(tunnel, 1);

return 0;
}
Expand Down Expand Up @@ -1838,9 +1870,9 @@ static bool ip6gre_netlink_encap_parms(struct nlattr *data[],
return ret;
}

static int ip6gre_newlink(struct net *src_net, struct net_device *dev,
struct nlattr *tb[], struct nlattr *data[],
struct netlink_ext_ack *extack)
static int ip6gre_newlink_common(struct net *src_net, struct net_device *dev,
struct nlattr *tb[], struct nlattr *data[],
struct netlink_ext_ack *extack)
{
struct ip6_tnl *nt;
struct net *net = dev_net(dev);
Expand Down Expand Up @@ -1877,49 +1909,76 @@ static int ip6gre_newlink(struct net *src_net, struct net_device *dev,
if (err)
goto out;

ip6gre_tnl_link_config(nt, !tb[IFLA_MTU]);

if (tb[IFLA_MTU])
ip6_tnl_change_mtu(dev, nla_get_u32(tb[IFLA_MTU]));

dev_hold(dev);
ip6gre_tunnel_link(ign, nt);

out:
return err;
}

static int ip6gre_changelink(struct net_device *dev, struct nlattr *tb[],
struct nlattr *data[],
struct netlink_ext_ack *extack)
static int ip6gre_newlink(struct net *src_net, struct net_device *dev,
struct nlattr *tb[], struct nlattr *data[],
struct netlink_ext_ack *extack)
{
int err = ip6gre_newlink_common(src_net, dev, tb, data, extack);
struct ip6_tnl *nt = netdev_priv(dev);
struct net *net = dev_net(dev);

if (!err) {
ip6gre_tnl_link_config(nt, !tb[IFLA_MTU]);
ip6gre_tunnel_link(net_generic(net, ip6gre_net_id), nt);
}
return err;
}

static struct ip6_tnl *
ip6gre_changelink_common(struct net_device *dev, struct nlattr *tb[],
struct nlattr *data[], struct __ip6_tnl_parm *p_p,
struct netlink_ext_ack *extack)
{
struct ip6_tnl *t, *nt = netdev_priv(dev);
struct net *net = nt->net;
struct ip6gre_net *ign = net_generic(net, ip6gre_net_id);
struct __ip6_tnl_parm p;
struct ip_tunnel_encap ipencap;

if (dev == ign->fb_tunnel_dev)
return -EINVAL;
return ERR_PTR(-EINVAL);

if (ip6gre_netlink_encap_parms(data, &ipencap)) {
int err = ip6_tnl_encap_setup(nt, &ipencap);

if (err < 0)
return err;
return ERR_PTR(err);
}

ip6gre_netlink_parms(data, &p);
ip6gre_netlink_parms(data, p_p);

t = ip6gre_tunnel_locate(net, &p, 0);
t = ip6gre_tunnel_locate(net, p_p, 0);

if (t) {
if (t->dev != dev)
return -EEXIST;
return ERR_PTR(-EEXIST);
} else {
t = nt;
}

return t;
}

static int ip6gre_changelink(struct net_device *dev, struct nlattr *tb[],
struct nlattr *data[],
struct netlink_ext_ack *extack)
{
struct ip6gre_net *ign = net_generic(dev_net(dev), ip6gre_net_id);
struct __ip6_tnl_parm p;
struct ip6_tnl *t;

t = ip6gre_changelink_common(dev, tb, data, &p, extack);
if (IS_ERR(t))
return PTR_ERR(t);

ip6gre_tunnel_unlink(ign, t);
ip6gre_tnl_change(t, &p, !tb[IFLA_MTU]);
ip6gre_tunnel_link(ign, t);
Expand Down Expand Up @@ -2071,6 +2130,53 @@ static void ip6erspan_tap_setup(struct net_device *dev)
netif_keep_dst(dev);
}

static int ip6erspan_newlink(struct net *src_net, struct net_device *dev,
struct nlattr *tb[], struct nlattr *data[],
struct netlink_ext_ack *extack)
{
int err = ip6gre_newlink_common(src_net, dev, tb, data, extack);
struct ip6_tnl *nt = netdev_priv(dev);
struct net *net = dev_net(dev);

if (!err) {
ip6erspan_tnl_link_config(nt, !tb[IFLA_MTU]);
ip6gre_tunnel_link(net_generic(net, ip6gre_net_id), nt);
}
return err;
}

static void ip6erspan_tnl_link_config(struct ip6_tnl *t, int set_mtu)
{
ip6gre_tnl_link_config_common(t);
ip6gre_tnl_link_config_route(t, set_mtu, ip6erspan_calc_hlen(t));
}

static int ip6erspan_tnl_change(struct ip6_tnl *t,
const struct __ip6_tnl_parm *p, int set_mtu)
{
ip6gre_tnl_copy_tnl_parm(t, p);
ip6erspan_tnl_link_config(t, set_mtu);
return 0;
}

static int ip6erspan_changelink(struct net_device *dev, struct nlattr *tb[],
struct nlattr *data[],
struct netlink_ext_ack *extack)
{
struct ip6gre_net *ign = net_generic(dev_net(dev), ip6gre_net_id);
struct __ip6_tnl_parm p;
struct ip6_tnl *t;

t = ip6gre_changelink_common(dev, tb, data, &p, extack);
if (IS_ERR(t))
return PTR_ERR(t);

ip6gre_tunnel_unlink(ign, t);
ip6erspan_tnl_change(t, &p, !tb[IFLA_MTU]);
ip6gre_tunnel_link(ign, t);
return 0;
}

static struct rtnl_link_ops ip6gre_link_ops __read_mostly = {
.kind = "ip6gre",
.maxtype = IFLA_GRE_MAX,
Expand Down Expand Up @@ -2107,8 +2213,8 @@ static struct rtnl_link_ops ip6erspan_tap_ops __read_mostly = {
.priv_size = sizeof(struct ip6_tnl),
.setup = ip6erspan_tap_setup,
.validate = ip6erspan_tap_validate,
.newlink = ip6gre_newlink,
.changelink = ip6gre_changelink,
.newlink = ip6erspan_newlink,
.changelink = ip6erspan_changelink,
.get_size = ip6gre_get_size,
.fill_info = ip6gre_fill_info,
.get_link_net = ip6_tnl_get_link_net,
Expand Down

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