net: Pass optional SKB and SK arguments to dst_ops->{update_pmtu,redirect}()

This will be used so that we can compose a full flow key.

Even though we have a route in this context, we need more.  In the
future the routes will be without destination address, source address,
etc. keying.  One ipv4 route will cover entire subnets, etc.

In this environment we have to have a way to possess persistent storage
for redirects and PMTU information.  This persistent storage will exist
in the FIB tables, and that's why we'll need to be able to rebuild a
full lookup flow key here.  Using that flow key will do a fib_lookup()
and create/update the persistent entry.

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2012-07-17 03:29:28 -07:00
parent 02f3d4ce9e
commit 6700c2709c
21 changed files with 71 additions and 49 deletions

View File

@ -1397,7 +1397,7 @@ void ipoib_cm_skb_too_long(struct net_device *dev, struct sk_buff *skb,
int e = skb_queue_empty(&priv->cm.skb_queue); int e = skb_queue_empty(&priv->cm.skb_queue);
if (skb_dst(skb)) if (skb_dst(skb))
skb_dst(skb)->ops->update_pmtu(skb_dst(skb), mtu); skb_dst(skb)->ops->update_pmtu(skb_dst(skb), NULL, skb, mtu);
skb_queue_tail(&priv->cm.skb_queue, skb); skb_queue_tail(&priv->cm.skb_queue, skb);
if (e) if (e)

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@ -24,8 +24,10 @@ struct dst_ops {
struct net_device *dev, int how); struct net_device *dev, int how);
struct dst_entry * (*negative_advice)(struct dst_entry *); struct dst_entry * (*negative_advice)(struct dst_entry *);
void (*link_failure)(struct sk_buff *); void (*link_failure)(struct sk_buff *);
void (*update_pmtu)(struct dst_entry *dst, u32 mtu); void (*update_pmtu)(struct dst_entry *dst, struct sock *sk,
void (*redirect)(struct dst_entry *dst, struct sk_buff *skb); struct sk_buff *skb, u32 mtu);
void (*redirect)(struct dst_entry *dst, struct sock *sk,
struct sk_buff *skb);
int (*local_out)(struct sk_buff *skb); int (*local_out)(struct sk_buff *skb);
struct neighbour * (*neigh_lookup)(const struct dst_entry *dst, struct neighbour * (*neigh_lookup)(const struct dst_entry *dst,
struct sk_buff *skb, struct sk_buff *skb,

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@ -111,11 +111,13 @@ static inline __be16 pppoe_proto(const struct sk_buff *skb)
pppoe_proto(skb) == htons(PPP_IPV6) && \ pppoe_proto(skb) == htons(PPP_IPV6) && \
brnf_filter_pppoe_tagged) brnf_filter_pppoe_tagged)
static void fake_update_pmtu(struct dst_entry *dst, u32 mtu) static void fake_update_pmtu(struct dst_entry *dst, struct sock *sk,
struct sk_buff *skb, u32 mtu)
{ {
} }
static void fake_redirect(struct dst_entry *dst, struct sk_buff *skb) static void fake_redirect(struct dst_entry *dst, struct sock *sk,
struct sk_buff *skb)
{ {
} }

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@ -193,7 +193,7 @@ static void dccp_do_redirect(struct sk_buff *skb, struct sock *sk)
struct dst_entry *dst = __sk_dst_check(sk, 0); struct dst_entry *dst = __sk_dst_check(sk, 0);
if (dst) if (dst)
dst->ops->redirect(dst, skb); dst->ops->redirect(dst, sk, skb);
} }
/* /*

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@ -134,7 +134,7 @@ static void dccp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
struct dst_entry *dst = __sk_dst_check(sk, np->dst_cookie); struct dst_entry *dst = __sk_dst_check(sk, np->dst_cookie);
if (dst) if (dst)
dst->ops->redirect(dst, skb); dst->ops->redirect(dst, sk, skb);
} }
if (type == ICMPV6_PKT_TOOBIG) { if (type == ICMPV6_PKT_TOOBIG) {

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@ -117,8 +117,10 @@ static void dn_dst_destroy(struct dst_entry *);
static void dn_dst_ifdown(struct dst_entry *, struct net_device *dev, int how); static void dn_dst_ifdown(struct dst_entry *, struct net_device *dev, int how);
static struct dst_entry *dn_dst_negative_advice(struct dst_entry *); static struct dst_entry *dn_dst_negative_advice(struct dst_entry *);
static void dn_dst_link_failure(struct sk_buff *); static void dn_dst_link_failure(struct sk_buff *);
static void dn_dst_update_pmtu(struct dst_entry *dst, u32 mtu); static void dn_dst_update_pmtu(struct dst_entry *dst, struct sock *sk,
static void dn_dst_redirect(struct dst_entry *dst, struct sk_buff *skb); struct sk_buff *skb , u32 mtu);
static void dn_dst_redirect(struct dst_entry *dst, struct sock *sk,
struct sk_buff *skb);
static struct neighbour *dn_dst_neigh_lookup(const struct dst_entry *dst, static struct neighbour *dn_dst_neigh_lookup(const struct dst_entry *dst,
struct sk_buff *skb, struct sk_buff *skb,
const void *daddr); const void *daddr);
@ -266,7 +268,8 @@ static int dn_dst_gc(struct dst_ops *ops)
* We update both the mtu and the advertised mss (i.e. the segment size we * We update both the mtu and the advertised mss (i.e. the segment size we
* advertise to the other end). * advertise to the other end).
*/ */
static void dn_dst_update_pmtu(struct dst_entry *dst, u32 mtu) static void dn_dst_update_pmtu(struct dst_entry *dst, struct sock *sk,
struct sk_buff *skb, u32 mtu)
{ {
struct dn_route *rt = (struct dn_route *) dst; struct dn_route *rt = (struct dn_route *) dst;
struct neighbour *n = rt->n; struct neighbour *n = rt->n;
@ -294,7 +297,8 @@ static void dn_dst_update_pmtu(struct dst_entry *dst, u32 mtu)
} }
} }
static void dn_dst_redirect(struct dst_entry *dst, struct sk_buff *skb) static void dn_dst_redirect(struct dst_entry *dst, struct sock *sk,
struct sk_buff *skb)
{ {
} }

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@ -840,7 +840,7 @@ struct dst_entry *inet_csk_update_pmtu(struct sock *sk, u32 mtu)
if (!dst) if (!dst)
goto out; goto out;
} }
dst->ops->update_pmtu(dst, mtu); dst->ops->update_pmtu(dst, sk, NULL, mtu);
dst = __sk_dst_check(sk, 0); dst = __sk_dst_check(sk, 0);
if (!dst) if (!dst)

View File

@ -833,7 +833,7 @@ static netdev_tx_t ipgre_tunnel_xmit(struct sk_buff *skb, struct net_device *dev
mtu = skb_dst(skb) ? dst_mtu(skb_dst(skb)) : dev->mtu; mtu = skb_dst(skb) ? dst_mtu(skb_dst(skb)) : dev->mtu;
if (skb_dst(skb)) if (skb_dst(skb))
skb_dst(skb)->ops->update_pmtu(skb_dst(skb), mtu); skb_dst(skb)->ops->update_pmtu(skb_dst(skb), NULL, skb, mtu);
if (skb->protocol == htons(ETH_P_IP)) { if (skb->protocol == htons(ETH_P_IP)) {
df |= (old_iph->frag_off&htons(IP_DF)); df |= (old_iph->frag_off&htons(IP_DF));

View File

@ -519,7 +519,7 @@ static netdev_tx_t ipip_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
} }
if (skb_dst(skb)) if (skb_dst(skb))
skb_dst(skb)->ops->update_pmtu(skb_dst(skb), mtu); skb_dst(skb)->ops->update_pmtu(skb_dst(skb), NULL, skb, mtu);
if ((old_iph->frag_off & htons(IP_DF)) && if ((old_iph->frag_off & htons(IP_DF)) &&
mtu < ntohs(old_iph->tot_len)) { mtu < ntohs(old_iph->tot_len)) {

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@ -148,8 +148,10 @@ static unsigned int ipv4_mtu(const struct dst_entry *dst);
static void ipv4_dst_destroy(struct dst_entry *dst); static void ipv4_dst_destroy(struct dst_entry *dst);
static struct dst_entry *ipv4_negative_advice(struct dst_entry *dst); static struct dst_entry *ipv4_negative_advice(struct dst_entry *dst);
static void ipv4_link_failure(struct sk_buff *skb); static void ipv4_link_failure(struct sk_buff *skb);
static void ip_rt_update_pmtu(struct dst_entry *dst, u32 mtu); static void ip_rt_update_pmtu(struct dst_entry *dst, struct sock *sk,
static void ip_do_redirect(struct dst_entry *dst, struct sk_buff *skb); struct sk_buff *skb, u32 mtu);
static void ip_do_redirect(struct dst_entry *dst, struct sock *sk,
struct sk_buff *skb);
static int rt_garbage_collect(struct dst_ops *ops); static int rt_garbage_collect(struct dst_ops *ops);
static void ipv4_dst_ifdown(struct dst_entry *dst, struct net_device *dev, static void ipv4_dst_ifdown(struct dst_entry *dst, struct net_device *dev,
@ -1273,7 +1275,7 @@ static void rt_del(unsigned int hash, struct rtable *rt)
spin_unlock_bh(rt_hash_lock_addr(hash)); spin_unlock_bh(rt_hash_lock_addr(hash));
} }
static void ip_do_redirect(struct dst_entry *dst, struct sk_buff *skb) static void ip_do_redirect(struct dst_entry *dst, struct sock *sk, struct sk_buff *skb)
{ {
__be32 new_gw = icmp_hdr(skb)->un.gateway; __be32 new_gw = icmp_hdr(skb)->un.gateway;
__be32 old_gw = ip_hdr(skb)->saddr; __be32 old_gw = ip_hdr(skb)->saddr;
@ -1506,7 +1508,8 @@ out: kfree_skb(skb);
return 0; return 0;
} }
static void ip_rt_update_pmtu(struct dst_entry *dst, u32 mtu) static void ip_rt_update_pmtu(struct dst_entry *dst, struct sock *sk,
struct sk_buff *skb, u32 mtu)
{ {
struct rtable *rt = (struct rtable *) dst; struct rtable *rt = (struct rtable *) dst;
@ -1531,7 +1534,7 @@ void ipv4_update_pmtu(struct sk_buff *skb, struct net *net, u32 mtu,
iph->daddr, iph->saddr, 0, 0); iph->daddr, iph->saddr, 0, 0);
rt = __ip_route_output_key(net, &fl4); rt = __ip_route_output_key(net, &fl4);
if (!IS_ERR(rt)) { if (!IS_ERR(rt)) {
ip_rt_update_pmtu(&rt->dst, mtu); ip_rt_update_pmtu(&rt->dst, NULL, skb, mtu);
ip_rt_put(rt); ip_rt_put(rt);
} }
} }
@ -1559,7 +1562,7 @@ void ipv4_redirect(struct sk_buff *skb, struct net *net,
protocol, flow_flags, iph->daddr, iph->saddr, 0, 0); protocol, flow_flags, iph->daddr, iph->saddr, 0, 0);
rt = __ip_route_output_key(net, &fl4); rt = __ip_route_output_key(net, &fl4);
if (!IS_ERR(rt)) { if (!IS_ERR(rt)) {
ip_do_redirect(&rt->dst, skb); ip_do_redirect(&rt->dst, NULL, skb);
ip_rt_put(rt); ip_rt_put(rt);
} }
} }
@ -2587,11 +2590,13 @@ static unsigned int ipv4_blackhole_mtu(const struct dst_entry *dst)
return mtu ? : dst->dev->mtu; return mtu ? : dst->dev->mtu;
} }
static void ipv4_rt_blackhole_update_pmtu(struct dst_entry *dst, u32 mtu) static void ipv4_rt_blackhole_update_pmtu(struct dst_entry *dst, struct sock *sk,
struct sk_buff *skb, u32 mtu)
{ {
} }
static void ipv4_rt_blackhole_redirect(struct dst_entry *dst, struct sk_buff *skb) static void ipv4_rt_blackhole_redirect(struct dst_entry *dst, struct sock *sk,
struct sk_buff *skb)
{ {
} }

View File

@ -319,7 +319,7 @@ static void do_redirect(struct sk_buff *skb, struct sock *sk)
struct dst_entry *dst = __sk_dst_check(sk, 0); struct dst_entry *dst = __sk_dst_check(sk, 0);
if (dst) if (dst)
dst->ops->redirect(dst, skb); dst->ops->redirect(dst, sk, skb);
} }
/* /*

View File

@ -194,20 +194,22 @@ static inline int xfrm4_garbage_collect(struct dst_ops *ops)
return (dst_entries_get_slow(ops) > ops->gc_thresh * 2); return (dst_entries_get_slow(ops) > ops->gc_thresh * 2);
} }
static void xfrm4_update_pmtu(struct dst_entry *dst, u32 mtu) static void xfrm4_update_pmtu(struct dst_entry *dst, struct sock *sk,
struct sk_buff *skb, u32 mtu)
{ {
struct xfrm_dst *xdst = (struct xfrm_dst *)dst; struct xfrm_dst *xdst = (struct xfrm_dst *)dst;
struct dst_entry *path = xdst->route; struct dst_entry *path = xdst->route;
path->ops->update_pmtu(path, mtu); path->ops->update_pmtu(path, sk, skb, mtu);
} }
static void xfrm4_redirect(struct dst_entry *dst, struct sk_buff *skb) static void xfrm4_redirect(struct dst_entry *dst, struct sock *sk,
struct sk_buff *skb)
{ {
struct xfrm_dst *xdst = (struct xfrm_dst *)dst; struct xfrm_dst *xdst = (struct xfrm_dst *)dst;
struct dst_entry *path = xdst->route; struct dst_entry *path = xdst->route;
path->ops->redirect(path, skb); path->ops->redirect(path, sk, skb);
} }
static void xfrm4_dst_destroy(struct dst_entry *dst) static void xfrm4_dst_destroy(struct dst_entry *dst)

View File

@ -269,7 +269,7 @@ struct dst_entry *inet6_csk_update_pmtu(struct sock *sk, u32 mtu)
if (IS_ERR(dst)) if (IS_ERR(dst))
return NULL; return NULL;
dst->ops->update_pmtu(dst, mtu); dst->ops->update_pmtu(dst, sk, NULL, mtu);
return inet6_csk_route_socket(sk); return inet6_csk_route_socket(sk);
} }

View File

@ -609,10 +609,10 @@ ip4ip6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
if (rel_info > dst_mtu(skb_dst(skb2))) if (rel_info > dst_mtu(skb_dst(skb2)))
goto out; goto out;
skb_dst(skb2)->ops->update_pmtu(skb_dst(skb2), rel_info); skb_dst(skb2)->ops->update_pmtu(skb_dst(skb2), NULL, skb2, rel_info);
} }
if (rel_type == ICMP_REDIRECT) if (rel_type == ICMP_REDIRECT)
skb_dst(skb2)->ops->redirect(skb_dst(skb2), skb2); skb_dst(skb2)->ops->redirect(skb_dst(skb2), NULL, skb2);
icmp_send(skb2, rel_type, rel_code, htonl(rel_info)); icmp_send(skb2, rel_type, rel_code, htonl(rel_info));
@ -952,7 +952,7 @@ static int ip6_tnl_xmit2(struct sk_buff *skb,
if (mtu < IPV6_MIN_MTU) if (mtu < IPV6_MIN_MTU)
mtu = IPV6_MIN_MTU; mtu = IPV6_MIN_MTU;
if (skb_dst(skb)) if (skb_dst(skb))
skb_dst(skb)->ops->update_pmtu(skb_dst(skb), mtu); skb_dst(skb)->ops->update_pmtu(skb_dst(skb), NULL, skb, mtu);
if (skb->len > mtu) { if (skb->len > mtu) {
*pmtu = mtu; *pmtu = mtu;
err = -EMSGSIZE; err = -EMSGSIZE;

View File

@ -78,8 +78,10 @@ static int ip6_dst_gc(struct dst_ops *ops);
static int ip6_pkt_discard(struct sk_buff *skb); static int ip6_pkt_discard(struct sk_buff *skb);
static int ip6_pkt_discard_out(struct sk_buff *skb); static int ip6_pkt_discard_out(struct sk_buff *skb);
static void ip6_link_failure(struct sk_buff *skb); static void ip6_link_failure(struct sk_buff *skb);
static void ip6_rt_update_pmtu(struct dst_entry *dst, u32 mtu); static void ip6_rt_update_pmtu(struct dst_entry *dst, struct sock *sk,
static void rt6_do_redirect(struct dst_entry *dst, struct sk_buff *skb); struct sk_buff *skb, u32 mtu);
static void rt6_do_redirect(struct dst_entry *dst, struct sock *sk,
struct sk_buff *skb);
#ifdef CONFIG_IPV6_ROUTE_INFO #ifdef CONFIG_IPV6_ROUTE_INFO
static struct rt6_info *rt6_add_route_info(struct net *net, static struct rt6_info *rt6_add_route_info(struct net *net,
@ -187,11 +189,13 @@ static unsigned int ip6_blackhole_mtu(const struct dst_entry *dst)
return mtu ? : dst->dev->mtu; return mtu ? : dst->dev->mtu;
} }
static void ip6_rt_blackhole_update_pmtu(struct dst_entry *dst, u32 mtu) static void ip6_rt_blackhole_update_pmtu(struct dst_entry *dst, struct sock *sk,
struct sk_buff *skb, u32 mtu)
{ {
} }
static void ip6_rt_blackhole_redirect(struct dst_entry *dst, struct sk_buff *skb) static void ip6_rt_blackhole_redirect(struct dst_entry *dst, struct sock *sk,
struct sk_buff *skb)
{ {
} }
@ -1071,7 +1075,8 @@ static void ip6_link_failure(struct sk_buff *skb)
} }
} }
static void ip6_rt_update_pmtu(struct dst_entry *dst, u32 mtu) static void ip6_rt_update_pmtu(struct dst_entry *dst, struct sock *sk,
struct sk_buff *skb, u32 mtu)
{ {
struct rt6_info *rt6 = (struct rt6_info*)dst; struct rt6_info *rt6 = (struct rt6_info*)dst;
@ -1108,7 +1113,7 @@ void ip6_update_pmtu(struct sk_buff *skb, struct net *net, __be32 mtu,
dst = ip6_route_output(net, NULL, &fl6); dst = ip6_route_output(net, NULL, &fl6);
if (!dst->error) if (!dst->error)
ip6_rt_update_pmtu(dst, ntohl(mtu)); ip6_rt_update_pmtu(dst, NULL, skb, ntohl(mtu));
dst_release(dst); dst_release(dst);
} }
EXPORT_SYMBOL_GPL(ip6_update_pmtu); EXPORT_SYMBOL_GPL(ip6_update_pmtu);
@ -1136,7 +1141,7 @@ void ip6_redirect(struct sk_buff *skb, struct net *net, int oif, u32 mark)
dst = ip6_route_output(net, NULL, &fl6); dst = ip6_route_output(net, NULL, &fl6);
if (!dst->error) if (!dst->error)
rt6_do_redirect(dst, skb); rt6_do_redirect(dst, NULL, skb);
dst_release(dst); dst_release(dst);
} }
EXPORT_SYMBOL_GPL(ip6_redirect); EXPORT_SYMBOL_GPL(ip6_redirect);
@ -1639,7 +1644,7 @@ static int ip6_route_del(struct fib6_config *cfg)
return err; return err;
} }
static void rt6_do_redirect(struct dst_entry *dst, struct sk_buff *skb) static void rt6_do_redirect(struct dst_entry *dst, struct sock *sk, struct sk_buff *skb)
{ {
struct net *net = dev_net(skb->dev); struct net *net = dev_net(skb->dev);
struct netevent_redirect netevent; struct netevent_redirect netevent;

View File

@ -807,7 +807,7 @@ static netdev_tx_t ipip6_tunnel_xmit(struct sk_buff *skb,
} }
if (tunnel->parms.iph.daddr && skb_dst(skb)) if (tunnel->parms.iph.daddr && skb_dst(skb))
skb_dst(skb)->ops->update_pmtu(skb_dst(skb), mtu); skb_dst(skb)->ops->update_pmtu(skb_dst(skb), NULL, skb, mtu);
if (skb->len > mtu) { if (skb->len > mtu) {
icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu); icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);

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@ -367,7 +367,7 @@ static void tcp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
struct dst_entry *dst = __sk_dst_check(sk, np->dst_cookie); struct dst_entry *dst = __sk_dst_check(sk, np->dst_cookie);
if (dst) if (dst)
dst->ops->redirect(dst,skb); dst->ops->redirect(dst, sk, skb);
} }
if (type == ICMPV6_PKT_TOOBIG) { if (type == ICMPV6_PKT_TOOBIG) {

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@ -207,20 +207,22 @@ static inline int xfrm6_garbage_collect(struct dst_ops *ops)
return dst_entries_get_fast(ops) > ops->gc_thresh * 2; return dst_entries_get_fast(ops) > ops->gc_thresh * 2;
} }
static void xfrm6_update_pmtu(struct dst_entry *dst, u32 mtu) static void xfrm6_update_pmtu(struct dst_entry *dst, struct sock *sk,
struct sk_buff *skb, u32 mtu)
{ {
struct xfrm_dst *xdst = (struct xfrm_dst *)dst; struct xfrm_dst *xdst = (struct xfrm_dst *)dst;
struct dst_entry *path = xdst->route; struct dst_entry *path = xdst->route;
path->ops->update_pmtu(path, mtu); path->ops->update_pmtu(path, sk, skb, mtu);
} }
static void xfrm6_redirect(struct dst_entry *dst, struct sk_buff *skb) static void xfrm6_redirect(struct dst_entry *dst, struct sock *sk,
struct sk_buff *skb)
{ {
struct xfrm_dst *xdst = (struct xfrm_dst *)dst; struct xfrm_dst *xdst = (struct xfrm_dst *)dst;
struct dst_entry *path = xdst->route; struct dst_entry *path = xdst->route;
path->ops->redirect(path, skb); path->ops->redirect(path, sk, skb);
} }
static void xfrm6_dst_destroy(struct dst_entry *dst) static void xfrm6_dst_destroy(struct dst_entry *dst)

View File

@ -797,7 +797,7 @@ ip_vs_tunnel_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
goto tx_error_put; goto tx_error_put;
} }
if (skb_dst(skb)) if (skb_dst(skb))
skb_dst(skb)->ops->update_pmtu(skb_dst(skb), mtu); skb_dst(skb)->ops->update_pmtu(skb_dst(skb), NULL, skb, mtu);
df |= (old_iph->frag_off & htons(IP_DF)); df |= (old_iph->frag_off & htons(IP_DF));
@ -913,7 +913,7 @@ ip_vs_tunnel_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
goto tx_error_put; goto tx_error_put;
} }
if (skb_dst(skb)) if (skb_dst(skb))
skb_dst(skb)->ops->update_pmtu(skb_dst(skb), mtu); skb_dst(skb)->ops->update_pmtu(skb_dst(skb), NULL, skb, mtu);
if (mtu < ntohs(old_iph->payload_len) + sizeof(struct ipv6hdr) && if (mtu < ntohs(old_iph->payload_len) + sizeof(struct ipv6hdr) &&
!skb_is_gso(skb)) { !skb_is_gso(skb)) {

View File

@ -432,7 +432,7 @@ void sctp_icmp_redirect(struct sock *sk, struct sctp_transport *t,
return; return;
dst = sctp_transport_dst_check(t); dst = sctp_transport_dst_check(t);
if (dst) if (dst)
dst->ops->redirect(dst, skb); dst->ops->redirect(dst, sk, skb);
} }
/* /*

View File

@ -249,7 +249,7 @@ void sctp_transport_update_pmtu(struct sock *sk, struct sctp_transport *t, u32 p
t->af_specific->get_dst(t, &t->saddr, &t->fl, sk); t->af_specific->get_dst(t, &t->saddr, &t->fl, sk);
if (dst) { if (dst) {
dst->ops->update_pmtu(dst, pmtu); dst->ops->update_pmtu(dst, sk, NULL, pmtu);
dst = sctp_transport_dst_check(t); dst = sctp_transport_dst_check(t);
if (!dst) if (!dst)