IPv6: Complete IPV6_DONTFRAG support

Finally add support to detect a local IPV6_DONTFRAG event
and return the relevant data to the user if they've enabled
IPV6_RECVPATHMTU on the socket.  The next recvmsg() will
return no data, but have an IPV6_PATHMTU as ancillary data.

Signed-off-by: Brian Haley <brian.haley@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

5 files changed, 112 insertions, 8 deletions

diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index 3192aa02ba5d..d2df3144429b 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -417,6 +417,9 @@ void inet6_destroy_sock(struct sock *sk)
         if ((skb = xchg(&np->pktoptions, NULL)) != NULL)
                 kfree_skb(skb);
 
+        if ((skb = xchg(&np->rxpmtu, NULL)) != NULL)
+                kfree_skb(skb);
+
         /* Free flowlabels */
         fl6_free_socklist(sk);
 
diff --git a/net/ipv6/datagram.c b/net/ipv6/datagram.c
index f5076d349b18..5959230bc6c1 100644
--- a/net/ipv6/datagram.c
+++ b/net/ipv6/datagram.c
@@ -278,6 +278,45 @@ void ipv6_local_error(struct sock *sk, int err, struct flowi *fl, u32 info)
                 kfree_skb(skb);
 }
 
+void ipv6_local_rxpmtu(struct sock *sk, struct flowi *fl, u32 mtu)
+{
+        struct ipv6_pinfo *np = inet6_sk(sk);
+        struct ipv6hdr *iph;
+        struct sk_buff *skb;
+        struct ip6_mtuinfo *mtu_info;
+
+        if (!np->rxopt.bits.rxpmtu)
+                return;
+
+        skb = alloc_skb(sizeof(struct ipv6hdr), GFP_ATOMIC);
+        if (!skb)
+                return;
+
+        skb_put(skb, sizeof(struct ipv6hdr));
+        skb_reset_network_header(skb);
+        iph = ipv6_hdr(skb);
+        ipv6_addr_copy(&iph->daddr, &fl->fl6_dst);
+
+        mtu_info = IP6CBMTU(skb);
+        if (!mtu_info) {
+                kfree_skb(skb);
+                return;
+        }
+
+        mtu_info->ip6m_mtu = mtu;
+        mtu_info->ip6m_addr.sin6_family = AF_INET6;
+        mtu_info->ip6m_addr.sin6_port = 0;
+        mtu_info->ip6m_addr.sin6_flowinfo = 0;
+        mtu_info->ip6m_addr.sin6_scope_id = fl->oif;
+        ipv6_addr_copy(&mtu_info->ip6m_addr.sin6_addr, &ipv6_hdr(skb)->daddr);
+
+        __skb_pull(skb, skb_tail_pointer(skb) - skb->data);
+        skb_reset_transport_header(skb);
+
+        skb = xchg(&np->rxpmtu, skb);
+        kfree_skb(skb);
+}
+
 /*
  *      Handle MSG_ERRQUEUE
  */
@@ -381,6 +420,54 @@ out:
         return err;
 }
 
+/*
+ *      Handle IPV6_RECVPATHMTU
+ */
+int ipv6_recv_rxpmtu(struct sock *sk, struct msghdr *msg, int len)
+{
+        struct ipv6_pinfo *np = inet6_sk(sk);
+        struct sk_buff *skb;
+        struct sockaddr_in6 *sin;
+        struct ip6_mtuinfo mtu_info;
+        int err;
+        int copied;
+
+        err = -EAGAIN;
+        skb = xchg(&np->rxpmtu, NULL);
+        if (skb == NULL)
+                goto out;
+
+        copied = skb->len;
+        if (copied > len) {
+                msg->msg_flags |= MSG_TRUNC;
+                copied = len;
+        }
+        err = skb_copy_datagram_iovec(skb, 0, msg->msg_iov, copied);
+        if (err)
+                goto out_free_skb;
+
+        sock_recv_timestamp(msg, sk, skb);
+
+        memcpy(&mtu_info, IP6CBMTU(skb), sizeof(mtu_info));
+
+        sin = (struct sockaddr_in6 *)msg->msg_name;
+        if (sin) {
+                sin->sin6_family = AF_INET6;
+                sin->sin6_flowinfo = 0;
+                sin->sin6_port = 0;
+                sin->sin6_scope_id = mtu_info.ip6m_addr.sin6_scope_id;
+                ipv6_addr_copy(&sin->sin6_addr, &mtu_info.ip6m_addr.sin6_addr);
+        }
+
+        put_cmsg(msg, SOL_IPV6, IPV6_PATHMTU, sizeof(mtu_info), &mtu_info);
+
+        err = copied;
+
+out_free_skb:
+        kfree_skb(skb);
+out:
+        return err;
+}
 
 
 int datagram_recv_ctl(struct sock *sk, struct msghdr *msg, struct sk_buff *skb)
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 54d43dd1f085..61e2bef56090 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1219,15 +1219,23 @@ int ip6_append_data(struct sock *sk, int getfrag(void *from, char *to,
          */
 
         inet->cork.length += length;
-        if (((length > mtu) && (sk->sk_protocol == IPPROTO_UDP)) &&
-            (rt->u.dst.dev->features & NETIF_F_UFO)) {
+        if (length > mtu) {
+                int proto = sk->sk_protocol;
+                if (dontfrag && (proto == IPPROTO_UDP || proto == IPPROTO_RAW)){
+                        ipv6_local_rxpmtu(sk, fl, mtu-exthdrlen);
+                        return -EMSGSIZE;
+                }
 
-                err = ip6_ufo_append_data(sk, getfrag, from, length, hh_len,
-                                          fragheaderlen, transhdrlen, mtu,
-                                          flags);
-                if (err)
-                        goto error;
-                return 0;
+                if (proto == IPPROTO_UDP &&
+                    (rt->u.dst.dev->features & NETIF_F_UFO)) {
+
+                        err = ip6_ufo_append_data(sk, getfrag, from, length,
+                                                  hh_len, fragheaderlen,
+                                                  transhdrlen, mtu, flags);
+                        if (err)
+                                goto error;
+                        return 0;
+                }
         }
 
         if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
diff --git a/net/ipv6/raw.c b/net/ipv6/raw.c
index 44a84ea9b3e8..85627386cb02 100644
--- a/net/ipv6/raw.c
+++ b/net/ipv6/raw.c
@@ -461,6 +461,9 @@ static int rawv6_recvmsg(struct kiocb *iocb, struct sock *sk,
         if (flags & MSG_ERRQUEUE)
                 return ipv6_recv_error(sk, msg, len);
 
+        if (np->rxpmtu && np->rxopt.bits.rxpmtu)
+                return ipv6_recv_rxpmtu(sk, msg, len);
+
         skb = skb_recv_datagram(sk, flags, noblock, &err);
         if (!skb)
                 goto out;
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 39e3665d9460..2850e35cee3d 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -335,6 +335,9 @@ int udpv6_recvmsg(struct kiocb *iocb, struct sock *sk,
         if (flags & MSG_ERRQUEUE)
                 return ipv6_recv_error(sk, msg, len);
 
+        if (np->rxpmtu && np->rxopt.bits.rxpmtu)
+                return ipv6_recv_rxpmtu(sk, msg, len);
+
 try_again:
         skb = __skb_recv_datagram(sk, flags | (noblock ? MSG_DONTWAIT : 0),
                                   &peeked, &err);