Commit 4f858c56 authored Apr 03, 2018 by Alexey Kodanev Committed by David S. Miller Apr 04, 2018

ipv6: udp: set dst cache for a connected sk if current not valid



A new RTF_CACHE route can be created between ip6_sk_dst_lookup_flow()
and ip6_dst_store() calls in udpv6_sendmsg(), when datagram sending
results to ICMPV6_PKT_TOOBIG error:

    udp_v6_send_skb(), for example with vti6 tunnel:
        vti6_xmit(), get ICMPV6_PKT_TOOBIG error
            skb_dst_update_pmtu(), can create a RTF_CACHE clone
            icmpv6_send()
    ...
    udpv6_err()
        ip6_sk_update_pmtu()
           ip6_update_pmtu(), can create a RTF_CACHE clone
           ...
           ip6_datagram_dst_update()
                ip6_dst_store()

And after commit 33c162a9 ("ipv6: datagram: Update dst cache of
a connected datagram sk during pmtu update"), the UDPv6 error handler
can update socket's dst cache, but it can happen before the update in
the end of udpv6_sendmsg(), preventing getting the new dst cache on
the next udpv6_sendmsg() calls.

In order to fix it, save dst in a connected socket only if the current
socket's dst cache is invalid.

The previous patch prepared ip6_sk_dst_lookup_flow() to do that with
the new argument, and this patch enables it in udpv6_sendmsg().

Fixes: 33c162a9 ("ipv6: datagram: Update dst cache of a connected datagram sk during pmtu update")
Fixes: 45e4fd26 ("ipv6: Only create RTF_CACHE routes after encountering pmtu exception")
Signed-off-by: Alexey Kodanev <alexey.kodanev@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 9f542f61

net/ipv6/udp.c

+2 −19

Original line number	Diff line number	Diff line
		@@ -1308,7 +1308,7 @@ int udpv6_sendmsg(struct sock sk, struct msghdr msg, size_t len)

		fl6.flowlabel = ip6_make_flowinfo(ipc6.tclass, fl6.flowlabel);

		dst = ip6_sk_dst_lookup_flow(sk, &fl6, final_p, false);
		dst = ip6_sk_dst_lookup_flow(sk, &fl6, final_p, connected);
		if (IS_ERR(dst)) {
		err = PTR_ERR(dst);
		dst = NULL;
		@@ -1333,7 +1333,7 @@ int udpv6_sendmsg(struct sock sk, struct msghdr msg, size_t len)
		err = PTR_ERR(skb);
		if (!IS_ERR_OR_NULL(skb))
		err = udp_v6_send_skb(skb, &fl6);
		goto release_dst;
		goto out;
		}

		lock_sock(sk);
		@@ -1367,23 +1367,6 @@ int udpv6_sendmsg(struct sock sk, struct msghdr msg, size_t len)
		err = np->recverr ? net_xmit_errno(err) : 0;
		release_sock(sk);

		release_dst:
		if (dst) {
		if (connected) {
		ip6_dst_store(sk, dst,
		ipv6_addr_equal(&fl6.daddr, &sk->sk_v6_daddr) ?
		&sk->sk_v6_daddr : NULL,
		#ifdef CONFIG_IPV6_SUBTREES
		ipv6_addr_equal(&fl6.saddr, &np->saddr) ?
		&np->saddr :
		#endif
		NULL);
		} else {
		dst_release(dst);
		}
		dst = NULL;
		}

		out:
		dst_release(dst);
		fl6_sock_release(flowlabel);