[ovs-dev] [PATCH ovn v4] Broadcast DHCPREPLY when BROADCAST flag is set

Ihar Hrachyshka ihrachys at redhat.com
Thu Mar 5 19:56:17 UTC 2020


As per RFC2131, section 4.1:
   A server or relay agent sending or relaying a DHCP message directly
   to a DHCP client (i.e., not to a relay agent specified in the
   'giaddr' field) SHOULD examine the BROADCAST bit in the 'flags'
   field.  If this bit is set to 1, the DHCP message SHOULD be sent as
   an IP broadcast using an IP broadcast address (preferably 0xffffffff)
   as the IP destination address and the link-layer broadcast address as
   the link-layer destination address.

This patch changes destination IP address to 255.255.255.255 when client
set BROADCAST flag in their DHCPREQUEST. Note: the offered IP address is
still part of the DHCP payload.

Reported-at: https://bugzilla.redhat.com/show_bug.cgi?id=1801006

Signed-off-by: Ihar Hrachyshka <ihrachys at redhat.com>

---

Version 4:
  * Introduced DHCP_BROADCAST_FLAG macro.
Version 3:
  * Converted DHCP_FLAGS_BROADCAST into a static function.
  * Used full sentences in comments (added missing dot).
  * Negated if-condition to handle least common case in else branch.
  * Fixed build with --enable-sparse --enable-Werror.
  * Updated ovn-northd documentation to reflect new flow actions.
Version 2:
  * Fixed line length warning reported by checkpatch.
---
 controller/pinctrl.c    | 15 +++++++
 lib/ovn-l7.h            |  2 +
 northd/ovn-northd.8.xml |  5 +--
 northd/ovn-northd.c     |  7 ++-
 tests/ovn.at            | 98 +++++++++++++++++++++++++++++------------
 5 files changed, 93 insertions(+), 34 deletions(-)

diff --git a/controller/pinctrl.c b/controller/pinctrl.c
index d06915a65..e135d5e0a 100644
--- a/controller/pinctrl.c
+++ b/controller/pinctrl.c
@@ -966,6 +966,12 @@ pinctrl_handle_tcp_reset(struct rconn *swconn, const struct flow *ip_flow,
     dp_packet_uninit(&packet);
 }
 
+static bool
+is_dhcp_flags_broadcast(ovs_be16 flags)
+{
+    return ntohs(flags) & DHCP_BROADCAST_FLAG;
+}
+
 /* Called with in the pinctrl_handler thread context. */
 static void
 pinctrl_handle_put_dhcp_opts(
@@ -1190,7 +1196,16 @@ pinctrl_handle_put_dhcp_opts(
 
     udp->udp_len = htons(new_l4_size);
 
+    /* Send a broadcast IP frame when BROADCAST flag is set. */
     struct ip_header *out_ip = dp_packet_l3(&pkt_out);
+    ovs_be32 ip_dst;
+    if (!is_dhcp_flags_broadcast(dhcp_data->flags)) {
+        ip_dst = *offer_ip;
+    } else {
+        ip_dst = htonl(0xffffffff);
+    }
+    put_16aligned_be32(&out_ip->ip_dst, ip_dst);
+
     out_ip->ip_tot_len = htons(pkt_out.l4_ofs - pkt_out.l3_ofs + new_l4_size);
     udp->udp_csum = 0;
     /* Checksum needs to be initialized to zero. */
diff --git a/lib/ovn-l7.h b/lib/ovn-l7.h
index f20d86c39..931e6ffcf 100644
--- a/lib/ovn-l7.h
+++ b/lib/ovn-l7.h
@@ -34,6 +34,8 @@ struct gen_opts_map {
     size_t code;
 };
 
+#define DHCP_BROADCAST_FLAG 0x8000
+
 #define DHCP_OPTION(NAME, CODE, TYPE) \
     {.name = NAME, .code = CODE, .type = TYPE}
 
diff --git a/northd/ovn-northd.8.xml b/northd/ovn-northd.8.xml
index a27dfa951..d37beafff 100644
--- a/northd/ovn-northd.8.xml
+++ b/northd/ovn-northd.8.xml
@@ -937,7 +937,6 @@ next;
         <pre>
 eth.dst = eth.src;
 eth.src = <var>E</var>;
-ip4.dst = <var>A</var>;
 ip4.src = <var>S</var>;
 udp.src = 67;
 udp.dst = 68;
@@ -948,8 +947,8 @@ output;
 
         <p>
           where <var>E</var> is the server MAC address and <var>S</var> is the
-          server IPv4 address defined in the DHCPv4 options and <var>A</var> is
-          the IPv4 address defined in the logical port's addresses column.
+          server IPv4 address defined in the DHCPv4 options. Note that
+          <code>ip4.dst</code> field is handled by <code>put_dhcp_opts</code>.
         </p>
 
         <p>
diff --git a/northd/ovn-northd.c b/northd/ovn-northd.c
index 3aba0487d..58dfee617 100644
--- a/northd/ovn-northd.c
+++ b/northd/ovn-northd.c
@@ -4271,10 +4271,9 @@ build_dhcpv4_action(struct ovn_port *op, ovs_be32 offer_ip,
     ds_put_cstr(options_action, "); next;");
 
     ds_put_format(response_action, "eth.dst = eth.src; eth.src = %s; "
-                  "ip4.dst = "IP_FMT"; ip4.src = %s; udp.src = 67; "
-                  "udp.dst = 68; outport = inport; flags.loopback = 1; "
-                  "output;",
-                  server_mac, IP_ARGS(offer_ip), server_ip);
+                  "ip4.src = %s; udp.src = 67; udp.dst = 68; "
+                  "outport = inport; flags.loopback = 1; output;",
+                  server_mac, server_ip);
 
     ds_put_format(ipv4_addr_match,
                   "ip4.src == "IP_FMT" && ip4.dst == {%s, 255.255.255.255}",
diff --git a/tests/ovn.at b/tests/ovn.at
index cbaa6d4a2..a7842a35e 100644
--- a/tests/ovn.at
+++ b/tests/ovn.at
@@ -4595,10 +4595,11 @@ sleep 2
 as hv1 ovs-vsctl show
 
 # This shell function sends a DHCP request packet
-# test_dhcp INPORT SRC_MAC DHCP_TYPE OFFER_IP REQUEST_IP ...
+# test_dhcp INPORT SRC_MAC DHCP_TYPE BROADCAST CIADDR OFFER_IP REQUEST_IP USE_IP ...
 test_dhcp() {
-    local inport=$1 src_mac=$2 dhcp_type=$3 ciaddr=$4 offer_ip=$5 request_ip=$6 use_ip=$7
-    shift; shift; shift; shift; shift; shift; shift;
+    local inport=$1 src_mac=$2 dhcp_type=$3 broadcast=$4 ciaddr=$5 offer_ip=$6 request_ip=$7 use_ip=$8
+    shift; shift; shift; shift; shift; shift; shift; shift;
+
     if test $use_ip != 0; then
         src_ip=$1
         dst_ip=$2
@@ -4607,6 +4608,7 @@ test_dhcp() {
         src_ip=`ip_to_hex 0 0 0 0`
         dst_ip=`ip_to_hex 255 255 255 255`
     fi
+
     if test $request_ip != 0; then
         ip_len=0120
         udp_len=010b
@@ -4614,10 +4616,19 @@ test_dhcp() {
         ip_len=011a
         udp_len=0106
     fi
+
+    if test $broadcast != 0; then
+        flags=8000
+        reply_dst_ip=`ip_to_hex 255 255 255 255`
+    else
+        flags=0000
+        reply_dst_ip=${offer_ip}
+    fi
+
     local request=ffffffffffff${src_mac}08004510${ip_len}0000000080110000${src_ip}${dst_ip}
     # udp header and dhcp header
     request=${request}00440043${udp_len}0000
-    request=${request}010106006359aa7600000000${ciaddr}000000000000000000000000${src_mac}
+    request=${request}010106006359aa760000${flags}${ciaddr}000000000000000000000000${src_mac}
     # client hardware padding
     request=${request}00000000000000000000
     # server hostname
@@ -4655,10 +4666,10 @@ test_dhcp() {
         ip_len=$(printf "%x" $ip_len)
         udp_len=$(printf "%x" $udp_len)
         # $ip_len var will be in 3 digits i.e 134. So adding a '0' before $ip_len
-        local reply=${src_mac}${srv_mac}080045100${ip_len}000000008011XXXX${srv_ip}${offer_ip}
+        local reply=${src_mac}${srv_mac}080045100${ip_len}000000008011XXXX${srv_ip}${reply_dst_ip}
         # udp header and dhcp header.
         # $udp_len var will be in 3 digits. So adding a '0' before $udp_len
-        reply=${reply}004300440${udp_len}0000020106006359aa7600000000${ciaddr}
+        reply=${reply}004300440${udp_len}0000020106006359aa760000${flags}${ciaddr}
         # your ip address; 0 for NAK
         if test $dhcp_reply_type = 06; then
             reply=${reply}00000000
@@ -4729,7 +4740,7 @@ server_ip=`ip_to_hex 10 0 0 1`
 ciaddr=`ip_to_hex 0 0 0 0`
 request_ip=0
 expected_dhcp_opts=330400000e100104ffffff0003040a00000136040a000001
-test_dhcp 1 f00000000001 01 $ciaddr $offer_ip $request_ip 0 ff1000000001 $server_ip 02 $expected_dhcp_opts
+test_dhcp 1 f00000000001 01 0 $ciaddr $offer_ip $request_ip 0 ff1000000001 $server_ip 02 $expected_dhcp_opts
 
 # NXT_RESUMEs should be 1.
 OVS_WAIT_UNTIL([test 1 = `cat ofctl_monitor*.log | grep -c NXT_RESUME`])
@@ -4755,7 +4766,7 @@ server_ip=`ip_to_hex 10 0 0 1`
 ciaddr=`ip_to_hex 0 0 0 0`
 request_ip=$offer_ip
 expected_dhcp_opts=330400000e100104ffffff0003040a00000136040a000001
-test_dhcp 2 f00000000002 03 $ciaddr $offer_ip $request_ip 0 ff1000000001 $server_ip 05 $expected_dhcp_opts
+test_dhcp 2 f00000000002 03 0 $ciaddr $offer_ip $request_ip 0 ff1000000001 $server_ip 05 $expected_dhcp_opts
 
 # NXT_RESUMEs should be 2.
 OVS_WAIT_UNTIL([test 2 = `cat ofctl_monitor*.log | grep -c NXT_RESUME`])
@@ -4779,7 +4790,7 @@ server_ip=`ip_to_hex 10 0 0 1`
 ciaddr=`ip_to_hex 0 0 0 0`
 request_ip=`ip_to_hex 10 0 0 7`
 expected_dhcp_opts=""
-test_dhcp 2 f00000000002 03 $ciaddr $offer_ip $request_ip 0 ff1000000001 $server_ip 06 $expected_dhcp_opts
+test_dhcp 2 f00000000002 03 0 $ciaddr $offer_ip $request_ip 0 ff1000000001 $server_ip 06 $expected_dhcp_opts
 
 # NXT_RESUMEs should be 3.
 OVS_WAIT_UNTIL([test 3 = `cat ofctl_monitor*.log | grep -c NXT_RESUME`])
@@ -4803,7 +4814,7 @@ rm -f 2.expected
 ciaddr=`ip_to_hex 0 0 0 0`
 offer_ip=0
 request_ip=0
-test_dhcp 2 f00000000002 08 $ciaddr $offer_ip $request_ip 0 1 1
+test_dhcp 2 f00000000002 08 0 $ciaddr $offer_ip $request_ip 0 1 1
 
 # NXT_RESUMEs should be 4.
 OVS_WAIT_UNTIL([test 4 = `cat ofctl_monitor*.log | grep -c NXT_RESUME`])
@@ -4820,12 +4831,12 @@ rm -f 2.expected
 # ls2-lp2 (vif4-tx.pcap) should receive the DHCPv4 request packet once.
 
 ciaddr=`ip_to_hex 0 0 0 0`
-test_dhcp 3 f00000000003 01 $ciaddr 0 0 4 0
+test_dhcp 3 f00000000003 01 0 $ciaddr 0 0 4 0
 
 # Send DHCPv4 packet on ls2-lp2. "router" DHCPv4 option is not defined for
 # this lport.
 ciaddr=`ip_to_hex 0 0 0 0`
-test_dhcp 4 f00000000004 01 $ciaddr 0 0 3 0
+test_dhcp 4 f00000000004 01 0 $ciaddr 0 0 3 0
 
 # NXT_RESUMEs should be 4.
 OVS_WAIT_UNTIL([test 4 = `cat ofctl_monitor*.log | grep -c NXT_RESUME`])
@@ -4842,7 +4853,7 @@ request_ip=0
 src_ip=$offer_ip
 dst_ip=$server_ip
 expected_dhcp_opts=330400000e100104ffffff0003040a00000136040a000001
-test_dhcp 2 f00000000002 03 $ciaddr $offer_ip $request_ip 1 $src_ip $dst_ip ff1000000001 $server_ip 05 $expected_dhcp_opts
+test_dhcp 2 f00000000002 03 0 $ciaddr $offer_ip $request_ip 1 $src_ip $dst_ip ff1000000001 $server_ip 05 $expected_dhcp_opts
 
 # NXT_RESUMEs should be 5.
 OVS_WAIT_UNTIL([test 5 = `cat ofctl_monitor*.log | grep -c NXT_RESUME`])
@@ -4868,7 +4879,7 @@ request_ip=0
 src_ip=$offer_ip
 dst_ip=`ip_to_hex 255 255 255 255`
 expected_dhcp_opts=330400000e100104ffffff0003040a00000136040a000001
-test_dhcp 2 f00000000002 03 $ciaddr $offer_ip $request_ip 1 $src_ip $dst_ip ff1000000001 $server_ip 05 $expected_dhcp_opts
+test_dhcp 2 f00000000002 03 0 $ciaddr $offer_ip $request_ip 1 $src_ip $dst_ip ff1000000001 $server_ip 05 $expected_dhcp_opts
 
 # NXT_RESUMEs should be 6.
 OVS_WAIT_UNTIL([test 6 = `cat ofctl_monitor*.log | grep -c NXT_RESUME`])
@@ -4894,7 +4905,7 @@ request_ip=0
 src_ip=$offer_ip
 dst_ip=`ip_to_hex 255 255 255 255`
 expected_dhcp_opts=""
-test_dhcp 2 f00000000002 03 $ciaddr $offer_ip $request_ip 1 $src_ip $dst_ip ff1000000001 $server_ip 06 $expected_dhcp_opts
+test_dhcp 2 f00000000002 03 0 $ciaddr $offer_ip $request_ip 1 $src_ip $dst_ip ff1000000001 $server_ip 06 $expected_dhcp_opts
 
 # NXT_RESUMEs should be 7.
 OVS_WAIT_UNTIL([test 7 = `cat ofctl_monitor*.log | grep -c NXT_RESUME`])
@@ -4920,7 +4931,7 @@ request_ip=0
 src_ip=$offer_ip
 dst_ip=`ip_to_hex 255 255 255 255`
 expected_dhcp_opts=""
-test_dhcp 2 f00000000002 03 $ciaddr $offer_ip $request_ip 1 $src_ip $dst_ip ff1000000001 $server_ip 06 $expected_dhcp_opts
+test_dhcp 2 f00000000002 03 0 $ciaddr $offer_ip $request_ip 1 $src_ip $dst_ip ff1000000001 $server_ip 06 $expected_dhcp_opts
 
 # NXT_RESUMEs should be 8.
 OVS_WAIT_UNTIL([test 8 = `cat ofctl_monitor*.log | grep -c NXT_RESUME`])
@@ -4942,7 +4953,7 @@ rm -f 2.expected
 ciaddr=`ip_to_hex 0 0 0 0`
 src_ip=`ip_to_hex 10 0 0 6`
 dst_ip=`ip_to_hex 10 0 0 4`
-test_dhcp 2 f00000000002 03 $ciaddr 0 0 1 $src_ip $dst_ip 1
+test_dhcp 2 f00000000002 03 0 $ciaddr 0 0 1 $src_ip $dst_ip 1
 
 # NXT_RESUMEs should be 8.
 OVS_WAIT_UNTIL([test 8 = `cat ofctl_monitor*.log | grep -c NXT_RESUME`])
@@ -4950,6 +4961,29 @@ OVS_WAIT_UNTIL([test 8 = `cat ofctl_monitor*.log | grep -c NXT_RESUME`])
 # vif1-tx.pcap should have received the DHCPv4 request packet
 OVN_CHECK_PACKETS([hv1/vif1-tx.pcap], [1.expected])
 
+reset_pcap_file hv1-vif1 hv1/vif1
+reset_pcap_file hv1-vif2 hv1/vif2
+rm -f 1.expected
+rm -f 2.expected
+
+# Send DHCPDISCOVER with BROADCAST flag on.
+offer_ip=`ip_to_hex 10 0 0 4`
+server_ip=`ip_to_hex 10 0 0 1`
+ciaddr=`ip_to_hex 0 0 0 0`
+request_ip=0
+expected_dhcp_opts=330400000e100104ffffff0003040a00000136040a000001
+test_dhcp 1 f00000000001 01 1 $ciaddr $offer_ip $request_ip 0 ff1000000001 $server_ip 02 $expected_dhcp_opts
+
+# NXT_RESUMEs should be 9.
+OVS_WAIT_UNTIL([test 9 = `cat ofctl_monitor*.log | grep -c NXT_RESUME`])
+
+$PYTHON "$ovs_srcdir/utilities/ovs-pcap.in" hv1/vif1-tx.pcap > 1.packets
+cat 1.expected | cut -c -48 > expout
+AT_CHECK([cat 1.packets | cut -c -48], [0], [expout])
+# Skipping the IPv4 checksum.
+cat 1.expected | cut -c 53- > expout
+AT_CHECK([cat 1.packets | cut -c 53-], [0], [expout])
+
 OVN_CLEANUP([hv1])
 
 AT_CLEANUP
@@ -13206,10 +13240,11 @@ as hv1
 ovs-vsctl show
 
 # This shell function sends a DHCP request packet
-# test_dhcp INPORT SRC_MAC DHCP_TYPE OFFER_IP ...
+# test_dhcp INPORT SRC_MAC DHCP_TYPE BROADCAST OFFER_IP ...
 test_dhcp() {
-    local inport=$1 src_mac=$2 dhcp_type=$3 offer_ip=$4 use_ip=$5
-    shift; shift; shift; shift; shift;
+    local inport=$1 src_mac=$2 dhcp_type=$3 broadcast=$4 offer_ip=$5 use_ip=$6
+    shift; shift; shift; shift; shift; shift;
+
     if test $use_ip != 0; then
         src_ip=$1
         dst_ip=$2
@@ -13218,10 +13253,19 @@ test_dhcp() {
         src_ip=`ip_to_hex 0 0 0 0`
         dst_ip=`ip_to_hex 255 255 255 255`
     fi
+
+    if test $broadcast != 0; then
+        flags=8000
+        reply_dst_ip=`ip_to_hex 255 255 255 255`
+    else
+        flags=0000
+        reply_dst_ip=${offer_ip}
+    fi
+
     local request=ffffffffffff${src_mac}0800451001100000000080110000${src_ip}${dst_ip}
     # udp header and dhcp header
     request=${request}0044004300fc0000
-    request=${request}010106006359aa760000000000000000000000000000000000000000${src_mac}
+    request=${request}010106006359aa760000${flags}00000000000000000000000000000000${src_mac}
     # client hardware padding
     request=${request}00000000000000000000
     # server hostname
@@ -13245,10 +13289,10 @@ test_dhcp() {
     ip_len=$(printf "%x" $ip_len)
     udp_len=$(printf "%x" $udp_len)
     # $ip_len var will be in 3 digits i.e 134. So adding a '0' before $ip_len
-    local reply=${src_mac}${srv_mac}080045100${ip_len}000000008011XXXX${srv_ip}${offer_ip}
+    local reply=${src_mac}${srv_mac}080045100${ip_len}000000008011XXXX${srv_ip}${reply_dst_ip}
     # udp header and dhcp header.
     # $udp_len var will be in 3 digits. So adding a '0' before $udp_len
-    reply=${reply}004300440${udp_len}0000020106006359aa760000000000000000
+    reply=${reply}004300440${udp_len}0000020106006359aa760000${flags}00000000
     # your ip address
     reply=${reply}${offer_ip}
     # next server ip address, relay agent ip address, client mac address
@@ -13367,7 +13411,7 @@ offer_ip=`ip_to_hex 10 0 0 6`
 server_ip=`ip_to_hex 10 0 0 1`
 server_mac=ff1000000001
 expected_dhcp_opts=330400000e100104ffffff0003040a00000136040a000001
-test_dhcp 1 f00000000003 01 $offer_ip 0 $server_mac $server_ip \
+test_dhcp 1 f00000000003 01 0 $offer_ip 0 $server_mac $server_ip \
 $expected_dhcp_opts
 
 # NXT_RESUMEs should be 1 in hv1.
@@ -13465,7 +13509,7 @@ offer_ip=`ip_to_hex 10 0 0 6`
 server_ip=`ip_to_hex 10 0 0 1`
 server_mac=ff1000000001
 expected_dhcp_opts=330400000e100104ffffff0003040a00000136040a000001
-test_dhcp 1 f00000000003 01 $offer_ip 0 $server_mac $server_ip \
+test_dhcp 1 f00000000003 01 0 $offer_ip 0 $server_mac $server_ip \
 $expected_dhcp_opts
 
 # NXT_RESUMEs should be 2 in hv1.
@@ -13575,7 +13619,7 @@ offer_ip=`ip_to_hex 10 0 0 6`
 server_ip=`ip_to_hex 10 0 0 1`
 server_mac=ff1000000001
 expected_dhcp_opts=330400000e100104ffffff0003040a00000136040a000001
-test_dhcp 1 f00000000003 01 $offer_ip 0 $server_mac $server_ip \
+test_dhcp 1 f00000000003 01 0 $offer_ip 0 $server_mac $server_ip \
 $expected_dhcp_opts
 
 # NXT_RESUMEs should be 3 in hv1.
@@ -13655,7 +13699,7 @@ offer_ip=`ip_to_hex 10 0 0 6`
 server_ip=`ip_to_hex 10 0 0 1`
 server_mac=ff1000000001
 expected_dhcp_opts=330400000e100104ffffff0003040a00000136040a000001
-test_dhcp 1 f00000000003 01 $offer_ip 0 $server_mac $server_ip \
+test_dhcp 1 f00000000003 01 0 $offer_ip 0 $server_mac $server_ip \
 $expected_dhcp_opts
 
 # NXT_RESUMEs should be 4 in hv1.
-- 
2.24.1



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