[PATCH RFC] ipvs: reschedule new connections if previous was on FIN_WAIT or TIME_WAIT

[Marcelo Ricardo Leitner <mleitner@xxxxxxxxxx>]

Signed-off-by: Marcelo Ricardo Leitner <mleitner@xxxxxxxxxx>
---

Notes:
    Hi,

    We have a report that not doing so may cause poor load balacing if
    applications reuse src port. With a patch like this, it would make
    new SYNs on a given connection to drop the old one and start a new
    one.

    One could say that this reuse can be done on purpose and carefully
    as a way to cause poor load balancing to cause a DoS.

    Thing is, I'm unsure if we really should do this, as it may end up
    doing more harm than good.

    WDYT? And if we do additional checks, like at least validating seq
    number, would it be better?

    Thanks,
    Marcelo

 net/netfilter/ipvs/ip_vs_core.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/net/netfilter/ipvs/ip_vs_core.c b/net/netfilter/ipvs/ip_vs_core.c
index 
990decba1fe418e36e59a1f081fcf0e47188da29..e81a9ac3c7e4e25fb14953b7faa4ace054f51274
 100644
--- a/net/netfilter/ipvs/ip_vs_core.c
+++ b/net/netfilter/ipvs/ip_vs_core.c
@@ -1036,6 +1036,14 @@ static inline bool is_new_conn(const struct sk_buff *skb,
        }
 }
 
+static inline bool is_new_conn_expected(const struct ip_vs_conn *cp)
+{
+       if (cp->protocol != IPPROTO_TCP)
+               return false;
+       return (cp->state == IP_VS_TCP_S_TIME_WAIT) ||
+               (cp->state == IP_VS_TCP_S_FIN_WAIT);
+}
+
 /* Handle response packets: rewrite addresses and send away...
  */
 static unsigned int
@@ -1642,9 +1650,10 @@ ip_vs_in(unsigned int hooknum, struct sk_buff *skb, int 
af)
         */
        cp = pp->conn_in_get(af, skb, &iph, 0);
 
-       if (unlikely(sysctl_expire_nodest_conn(ipvs)) && cp && cp->dest &&
-           unlikely(!atomic_read(&cp->dest->weight)) && !iph.fragoffs &&
-           is_new_conn(skb, &iph)) {
+       if (cp && cp->dest && !iph.fragoffs && is_new_conn(skb, &iph) &&
+           ((unlikely(sysctl_expire_nodest_conn(ipvs)) &&
+             unlikely(!atomic_read(&cp->dest->weight))) ||
+            unlikely(is_new_conn_expected(cp)))) {
                ip_vs_conn_expire_now(cp);
                __ip_vs_conn_put(cp);
                cp = NULL;
-- 
1.9.3

--
To unsubscribe from this list: send the line "unsubscribe lvs-devel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html