From f395e75e27323cc1ef060f640d0d535ed50e705d Mon Sep 17 00:00:00 2001 From: Gerhard Sittig Date: Fri, 12 Sep 2014 08:48:15 +0200 Subject: [PATCH] net: dns: fix for DNS queries sent to the wrong MAC address When a DNS query is sent out, the ethernet packet can get directed to the MAC address of a server that was communicated to before. This is wrong when the previously stored MAC address corresponds to a different server's IP address, i.e. when the IP address of the previous and the current communication are different. The error can get reproduced by running a sequence of e.g. a TFTP download and a DNS query, where the TFTP and DNS servers reside on individual machines. The fix is to clear the server's MAC address that might be left from a previous operation, and to fetch the peer's MAC address in a new ARP lookup, before the DNS query is sent. This is the approach taken in other network services, like 8e52533d1095 ("net: tftpsrv: Get correct client MAC address"). Reported-by: Dirk Zimoch Signed-off-by: Gerhard Sittig --- net/dns.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/dns.c b/net/dns.c index ff9ddffc9d..dd45320150 100644 --- a/net/dns.c +++ b/net/dns.c @@ -202,5 +202,8 @@ DnsStart(void) NetSetTimeout(DNS_TIMEOUT, DnsTimeout); net_set_udp_handler(DnsHandler); + /* Clear a previous MAC address, the server IP might have changed. */ + memset(NetServerEther, 0, sizeof(NetServerEther)); + DnsSend(); } -- 2.39.2