Merge ~fnordahl/ubuntu/+source/ovn:bug/1857026-focal into ~ubuntu-server-dev/ubuntu/+source/ovn:ubuntu/focal

[Frode Nordahl]

[Frode Nordahl (fnordahl)]

Package building in https://launchpad.net/~fnordahl/+archive/ubuntu/lp1857026

diff --git a/debian/changelog b/debian/changelog
index c0af91d..2094609 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,3 +1,11 @@
+ovn (20.03.2-0ubuntu0.20.04.3) focal; urgency=medium
+
+  * Add support for PTR DNS requests (LP: #1857026)
+    - d/p/lp-1857026-0001-DNS-Make-DNS-lookups-case-insensitive.patch
+    - d/p/lp-1857026-0002-controller-Add-support-for-PTR-DNS-requests.patch
+
+ -- Frode Nordahl <[e-mail]>  Thu, 06 Jan 2022 10:00:00 +0100
+
 ovn (20.03.2-0ubuntu0.20.04.2) focal; urgency=medium
 
   * Add RBAC rules for IGMP_Group table (LP: #1914988):
diff --git a/debian/patches/lp-1857026-0001-DNS-Make-DNS-lookups-case-insensitive.patch b/debian/patches/lp-1857026-0001-DNS-Make-DNS-lookups-case-insensitive.patch
new file mode 100644
index 0000000..bfb394a
--- /dev/null
+++ b/debian/patches/lp-1857026-0001-DNS-Make-DNS-lookups-case-insensitive.patch
@@ -0,0 +1,274 @@
+Origin: backport, https://github.com/ovn-org/ovn/commit/9287f425e8bc5781728b2ff1c60413d3c39c33a8
+Bug-Ubuntu: https://bugs.launchpad.net/ubuntu/+source/ovn/+bug/1857026
+Last-Update: 2022-01-06
+
+From 815d4c04992d994bcd75b3d642fe6cc694ec99b3 Mon Sep 17 00:00:00 2001
+From: Mark Michelson <[e-mail]>
+Date: Mon, 20 Apr 2020 09:25:09 -0400
+Subject: [PATCH 1/2] DNS: Make DNS lookups case insensitive.
+
+From RFC 1035 Section 2.3.3:
+
+"For all parts of the DNS that are part of the official protocol, all
+comparisons between character strings (e.g., labels, domain names, etc.)
+are done in a case-insensitive manner."
+
+OVN was using case-sensitive lookups and therefore was not complying.
+This change makes lookups case insensitive by storing lowercase record
+names in the southbound database and converting incoming query names to
+lowercase.
+
+Signed-off-by: Mark Michelson <[e-mail]>
+Reported-at: https://bugzilla.redhat.com/show_bug.cgi?id=1819069
+Reported-by: Jianlin Shi <[e-mail]>
+Acked-by: Numan Siddique <[e-mail]>
+(cherry picked from commit 9287f425e8bc5781728b2ff1c60413d3c39c33a8)
+---
+ controller/pinctrl.c |  7 ++++-
+ lib/ovn-util.c       | 15 +++++++++++
+ lib/ovn-util.h       |  5 ++++
+ northd/ovn-northd.c  | 15 ++++++++++-
+ ovn-sb.xml           |  3 ++-
+ tests/ovn.at         | 61 ++++++++++++++++++++++++++++++++------------
+ 6 files changed, 87 insertions(+), 19 deletions(-)
+
+diff --git a/controller/pinctrl.c b/controller/pinctrl.c
+index 5822f03ef..4879dcc45 100644
+--- a/controller/pinctrl.c
++++ b/controller/pinctrl.c
+@@ -1767,7 +1767,12 @@ pinctrl_handle_dns_lookup(
+         struct dns_data *d = iter->data;
+         for (size_t i = 0; i < d->n_dps; i++) {
+             if (d->dps[i] == dp_key) {
+-                answer_ips = smap_get(&d->records, ds_cstr(&query_name));
++                /* DNS records in SBDB are stored in lowercase. Convert to
++                 * lowercase to perform case insensitive lookup
++                 */
++                char *query_name_lower = str_tolower(ds_cstr(&query_name));
++                answer_ips = smap_get(&d->records, query_name_lower);
++                free(query_name_lower);
+                 if (answer_ips) {
+                     break;
+                 }
+diff --git a/lib/ovn-util.c b/lib/ovn-util.c
+index 514e2489f..1b30c2e9a 100644
+--- a/lib/ovn-util.c
++++ b/lib/ovn-util.c
+@@ -21,6 +21,7 @@
+ #include "openvswitch/ofp-parse.h"
+ #include "ovn-nb-idl.h"
+ #include "ovn-sb-idl.h"
++#include <ctype.h>
+ 
+ VLOG_DEFINE_THIS_MODULE(ovn_util);
+ 
+@@ -550,3 +551,17 @@ ip46_equals(const struct v46_ip *addr1, const struct v46_ip *addr2)
+             (addr1->family == AF_INET ? addr1->ipv4 == addr2->ipv4 :
+              IN6_ARE_ADDR_EQUAL(&addr1->ipv6, &addr2->ipv6)));
+ }
++
++char *
++str_tolower(const char *orig)
++{
++    char *copy = xmalloc(strlen(orig) + 1);
++    char *p = copy;
++
++    while (*orig) {
++        *p++ = tolower(*orig++);
++    }
++    *p = '\0';
++
++    return copy;
++}
+diff --git a/lib/ovn-util.h b/lib/ovn-util.h
+index 11238f61c..4076e8b9a 100644
+--- a/lib/ovn-util.h
++++ b/lib/ovn-util.h
+@@ -124,4 +124,9 @@ struct v46_ip {
+ bool ip46_parse_cidr(const char *str, struct v46_ip *prefix,
+                      unsigned int *plen);
+ bool ip46_equals(const struct v46_ip *addr1, const struct v46_ip *addr2);
++
++/* Returns a lowercase copy of orig.
++ * Caller must free the returned string.
++ */
++char *str_tolower(const char *orig);
+ #endif
+diff --git a/northd/ovn-northd.c b/northd/ovn-northd.c
+index 9cc2c04bb..4ced1b48f 100644
+--- a/northd/ovn-northd.c
++++ b/northd/ovn-northd.c
+@@ -10634,7 +10634,20 @@ sync_dns_entries(struct northd_context *ctx, struct hmap *datapaths)
+             dns_info->sb_dns,
+             (struct sbrec_datapath_binding **)dns_info->sbs,
+             dns_info->n_sbs);
+-        sbrec_dns_set_records(dns_info->sb_dns, &dns_info->nb_dns->records);
++
++        /* DNS lookups are case-insensitive. Convert records to lowercase so
++         * we can do consistent lookups when DNS requests arrive
++         */
++        struct smap lower_records = SMAP_INITIALIZER(&lower_records);
++        struct smap_node *node;
++        SMAP_FOR_EACH (node, &dns_info->nb_dns->records) {
++            smap_add_nocopy(&lower_records, xstrdup(node->key),
++                            str_tolower(node->value));
++        }
++
++        sbrec_dns_set_records(dns_info->sb_dns, &lower_records);
++
++        smap_destroy(&lower_records);
+         free(dns_info->sbs);
+         free(dns_info);
+     }
+diff --git a/ovn-sb.xml b/ovn-sb.xml
+index 2703e6d0c..64c33d2df 100644
+--- a/ovn-sb.xml
++++ b/ovn-sb.xml
+@@ -3581,7 +3581,8 @@ tcp.flags = RST;
+     <column name="records">
+       Key-value pair of DNS records with <code>DNS query name</code> as the key
+       and a string of IP address(es) separated by comma or space as the
+-      value.
++      value. ovn-northd stores the DNS query name in all lowercase in order to
++      facilitate case-insensitive lookups.
+ 
+       <p><b>Example: </b> "vm1.ovn.org" = "10.0.0.4 aef0::4"</p>
+     </column>
+diff --git a/tests/ovn.at b/tests/ovn.at
+index 4d9ee1256..b6eff4349 100644
+--- a/tests/ovn.at
++++ b/tests/ovn.at
+@@ -8317,6 +8317,12 @@ set_dns_params() {
+         # IPv4 address - 10.0.0.4
+         expected_dns_answer=${query_name}00010001${ttl}00040a000004
+         ;;
++    VM1)
++        # VM1.OVN.ORG
++        query_name=03564d31034f564e034f524700
++        # IPv4 address - 10.0.0.4
++        expected_dns_answer=${query_name}00010001${ttl}00040a000004
++        ;;
+     vm2)
+         # vm2.ovn.org
+         query_name=03766d32036f766e036f726700
+@@ -8479,6 +8485,29 @@ reset_pcap_file hv1-vif2 hv1/vif2
+ rm -f 1.expected
+ rm -f 2.expected
+ 
++# Try vm1 again but an all-caps query name
++
++set_dns_params VM1
++src_ip=`ip_to_hex 10 0 0 6`
++dst_ip=`ip_to_hex 10 0 0 1`
++dns_reply=1
++test_dns 2 f00000000002 f000000000f0 $src_ip $dst_ip $dns_reply $dns_req_data $dns_resp_data
++
++# NXT_RESUMEs should be 3.
++OVS_WAIT_UNTIL([test 3 = `cat ofctl_monitor*.log | grep -c NXT_RESUME`])
++
++$PYTHON "$ovs_srcdir/utilities/ovs-pcap.in" hv1/vif2-tx.pcap > 2.packets
++cat 2.expected | cut -c -48 > expout
++AT_CHECK([cat 2.packets | cut -c -48], [0], [expout])
++# Skipping the IPv4 checksum.
++cat 2.expected | cut -c 53- > expout
++AT_CHECK([cat 2.packets | cut -c 53-], [0], [expout])
++
++reset_pcap_file hv1-vif1 hv1/vif1
++reset_pcap_file hv1-vif2 hv1/vif2
++rm -f 1.expected
++rm -f 2.expected
++
+ # Clear the query name options for ls1-lp2
+ ovn-nbctl --wait=hv remove DNS $DNS1 records vm2.ovn.org
+ 
+@@ -8488,8 +8517,8 @@ dst_ip=`ip_to_hex 10 0 0 1`
+ dns_reply=0
+ test_dns 1 f00000000001 f00000000002 $src_ip $dst_ip $dns_reply $dns_req_data
+ 
+-# NXT_RESUMEs should be 3.
+-OVS_WAIT_UNTIL([test 3 = `cat ofctl_monitor*.log | grep -c NXT_RESUME`])
++# NXT_RESUMEs should be 4.
++OVS_WAIT_UNTIL([test 4 = `cat ofctl_monitor*.log | grep -c NXT_RESUME`])
+ 
+ $PYTHON "$ovs_srcdir/utilities/ovs-pcap.in" hv1/vif1-tx.pcap > 1.packets
+ AT_CHECK([cat 1.packets], [0], [])
+@@ -8510,8 +8539,8 @@ dst_ip=`ip_to_hex 10 0 0 1`
+ dns_reply=0
+ test_dns 2 f00000000002 f000000000f0 $src_ip $dst_ip $dns_reply $dns_req_data
+ 
+-# NXT_RESUMEs should be 3 only.
+-OVS_WAIT_UNTIL([test 3 = `cat ofctl_monitor*.log | grep -c NXT_RESUME`])
++# NXT_RESUMEs should be 4 only.
++OVS_WAIT_UNTIL([test 4 = `cat ofctl_monitor*.log | grep -c NXT_RESUME`])
+ 
+ $PYTHON "$ovs_srcdir/utilities/ovs-pcap.in" hv1/vif2-tx.pcap > 2.packets
+ AT_CHECK([cat 2.packets], [0], [])
+@@ -8531,8 +8560,8 @@ dst_ip=`ip_to_hex 10 0 0 1`
+ dns_reply=1
+ test_dns 2 f00000000002 f000000000f0 $src_ip $dst_ip $dns_reply $dns_req_data $dns_resp_data
+ 
+-# NXT_RESUMEs should be 4.
+-OVS_WAIT_UNTIL([test 4 = `cat ofctl_monitor*.log | grep -c NXT_RESUME`])
++# NXT_RESUMEs should be 5.
++OVS_WAIT_UNTIL([test 5 = `cat ofctl_monitor*.log | grep -c NXT_RESUME`])
+ 
+ $PYTHON "$ovs_srcdir/utilities/ovs-pcap.in" hv1/vif2-tx.pcap > 2.packets
+ cat 2.expected | cut -c -48 > expout
+@@ -8553,8 +8582,8 @@ dst_ip=`ip_to_hex 10 0 0 1`
+ dns_reply=1
+ test_dns 2 f00000000002 f000000000f0 $src_ip $dst_ip $dns_reply $dns_req_data $dns_resp_data
+ 
+-# NXT_RESUMEs should be 5.
+-OVS_WAIT_UNTIL([test 5 = `cat ofctl_monitor*.log | grep -c NXT_RESUME`])
++# NXT_RESUMEs should be 6.
++OVS_WAIT_UNTIL([test 6 = `cat ofctl_monitor*.log | grep -c NXT_RESUME`])
+ 
+ $PYTHON "$ovs_srcdir/utilities/ovs-pcap.in" hv1/vif2-tx.pcap > 2.packets
+ cat 2.expected | cut -c -48 > expout
+@@ -8575,8 +8604,8 @@ dst_ip=`ip_to_hex 10 0 0 1`
+ dns_reply=0
+ test_dns 2 f00000000002 f000000000f0 $src_ip $dst_ip $dns_reply $dns_req_data
+ 
+-# NXT_RESUMEs should be 6.
+-OVS_WAIT_UNTIL([test 6 = `cat ofctl_monitor*.log | grep -c NXT_RESUME`])
++# NXT_RESUMEs should be 7.
++OVS_WAIT_UNTIL([test 7 = `cat ofctl_monitor*.log | grep -c NXT_RESUME`])
+ 
+ $PYTHON "$ovs_srcdir/utilities/ovs-pcap.in" hv1/vif2-tx.pcap > 2.packets
+ AT_CHECK([cat 2.packets], [0], [])
+@@ -8593,8 +8622,8 @@ dst_ip=`ip_to_hex 10 0 0 1`
+ dns_reply=0
+ test_dns 2 f00000000002 f000000000f0 $src_ip $dst_ip $dns_reply $dns_req_data
+ 
+-# NXT_RESUMEs should be 7.
+-OVS_WAIT_UNTIL([test 7 = `cat ofctl_monitor*.log | grep -c NXT_RESUME`])
++# NXT_RESUMEs should be 8.
++OVS_WAIT_UNTIL([test 8 = `cat ofctl_monitor*.log | grep -c NXT_RESUME`])
+ 
+ $PYTHON "$ovs_srcdir/utilities/ovs-pcap.in" hv1/vif2-tx.pcap > 2.packets
+ AT_CHECK([cat 2.packets], [0], [])
+@@ -8613,8 +8642,8 @@ dst_ip=`ip_to_hex 10 0 0 1`
+ dns_reply=1
+ test_dns 1 f00000000001 f000000000f0 $src_ip $dst_ip $dns_reply $dns_req_data $dns_resp_data
+ 
+-# NXT_RESUMEs should be 8.
+-OVS_WAIT_UNTIL([test 8 = `cat ofctl_monitor*.log | grep -c NXT_RESUME`])
++# 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
+@@ -8635,8 +8664,8 @@ dst_ip=aef00000000000000000000000000001
+ dns_reply=1
+ test_dns6 1 f00000000001 f000000000f0 $src_ip $dst_ip $dns_reply $dns_req_data $dns_resp_data
+ 
+-# NXT_RESUMEs should be 9.
+-OVS_WAIT_UNTIL([test 9 = `cat ofctl_monitor*.log | grep -c NXT_RESUME`])
++# NXT_RESUMEs should be 10
++OVS_WAIT_UNTIL([test 10 = `cat ofctl_monitor*.log | grep -c NXT_RESUME`])
+ 
+ $PYTHON "$ovs_srcdir/utilities/ovs-pcap.in" hv1/vif1-tx.pcap > 1.packets
+ # Skipping the UDP checksum.
+-- 
+2.33.1
+
diff --git a/debian/patches/lp-1857026-0002-controller-Add-support-for-PTR-DNS-requests.patch b/debian/patches/lp-1857026-0002-controller-Add-support-for-PTR-DNS-requests.patch
new file mode 100644
index 0000000..4386c6c
--- /dev/null
+++ b/debian/patches/lp-1857026-0002-controller-Add-support-for-PTR-DNS-requests.patch
@@ -0,0 +1,491 @@
+Origin: backport, https://github.com/ovn-org/ovn/commit/82a4e44e308171cb545211eb2534475ef16a4c0e
+Bug-Ubuntu: https://bugs.launchpad.net/ubuntu/+source/ovn/+bug/1857026
+Last-Update: 2022-01-06
+
+From e612a270f789af616e98cc204eee42b8b114de41 Mon Sep 17 00:00:00 2001
+From: Vladislav Odintsov <[e-mail]>
+Date: Fri, 19 Feb 2021 11:57:59 +0300
+Subject: [PATCH 2/2] controller: Add support for PTR DNS requests.
+
+The native OVN DNS support doesn't yet support for PTR DNS requests.
+This patch adds the support for it.  If suppose there is a dns record
+as - "vm1.ovn.org"="10.0.0.4", then a normal DNS request will query for
+"vm1.ovn.org" and the reply will be the IP address - 10.0.0.4.
+PTR DNS request helps in getting the domain name of the IP address.
+For the above example, the PTR DNS request will have a query name as
+- "4.0.0.10.in-addr.arpa".  And the response will have "vm1.ovn.org".
+In order to support this feature, this patch expects the CMS to define
+an another entry in the DNS record  as - "4.0.0.10.in-addr.arpa"="vm1.ovn.org".
+
+This makes the job of ovn-controller easier to support this feature.
+
+Submitted-at: https://github.com/ovn-org/ovn/pull/74
+Signed-off-by: Vladislav Odintsov <[e-mail]>
+Signed-off-by: Numan Siddique <[e-mail]>
+(cherry picked from commit 82a4e44e308171cb545211eb2534475ef16a4c0e)
+---
+ controller/pinctrl.c | 181 +++++++++++++++++++++++++++++++------------
+ lib/ovn-l7.h         |   8 ++
+ ovn-nb.xml           |   6 ++
+ tests/ovn.at         |  83 +++++++++++++++++++-
+ 4 files changed, 228 insertions(+), 50 deletions(-)
+
+diff --git a/controller/pinctrl.c b/controller/pinctrl.c
+index 4879dcc45..c505077e0 100644
+--- a/controller/pinctrl.c
++++ b/controller/pinctrl.c
+@@ -1658,6 +1658,106 @@ destroy_dns_cache(void)
+     }
+ }
+ 
++/* Populates dns_answer struct with base data.
++ * Copy the answer section
++ * Format of the answer section is
++ *  - NAME     -> The domain name
++ *  - TYPE     -> 2 octets containing one of the RR type codes
++ *  - CLASS    -> 2 octets which specify the class of the data
++ *                in the RDATA field.
++ *  - TTL      -> 32 bit unsigned int specifying the time
++ *                interval (in secs) that the resource record
++ *                 may be cached before it should be discarded.
++ *  - RDLENGTH -> 16 bit integer specifying the length of the
++ *                RDATA field.
++ *  - RDATA    -> a variable length string of octets that
++ *                describes the resource.
++ */
++static void
++dns_build_base_answer(
++    struct ofpbuf *dns_answer, const uint8_t *in_queryname,
++    uint16_t query_length, int query_type)
++{
++    ofpbuf_put(dns_answer, in_queryname, query_length);
++    put_be16(dns_answer, htons(query_type));
++    put_be16(dns_answer, htons(DNS_CLASS_IN));
++    put_be32(dns_answer, htonl(DNS_DEFAULT_RR_TTL));
++}
++
++/* Populates dns_answer struct with a TYPE A answer. */
++static void
++dns_build_a_answer(
++    struct ofpbuf *dns_answer, const uint8_t *in_queryname,
++    uint16_t query_length, const ovs_be32 addr)
++{
++    dns_build_base_answer(dns_answer, in_queryname, query_length,
++                          DNS_QUERY_TYPE_A);
++    put_be16(dns_answer, htons(sizeof(ovs_be32)));
++    put_be32(dns_answer, addr);
++}
++
++/* Populates dns_answer struct with a TYPE AAAA answer. */
++static void
++dns_build_aaaa_answer(
++    struct ofpbuf *dns_answer, const uint8_t *in_queryname,
++    uint16_t query_length, const struct in6_addr *addr)
++{
++    dns_build_base_answer(dns_answer, in_queryname, query_length,
++                          DNS_QUERY_TYPE_AAAA);
++    put_be16(dns_answer, htons(sizeof(*addr)));
++    ofpbuf_put(dns_answer, addr, sizeof(*addr));
++}
++
++/* Populates dns_answer struct with a TYPE PTR answer. */
++static void
++dns_build_ptr_answer(
++    struct ofpbuf *dns_answer, const uint8_t *in_queryname,
++    uint16_t query_length, const char *answer_data)
++{
++    char *encoded_answer;
++    uint16_t encoded_answer_length;
++
++    dns_build_base_answer(dns_answer, in_queryname, query_length,
++                          DNS_QUERY_TYPE_PTR);
++
++    /* Initialize string 2 chars longer than real answer:
++     * first label length and terminating zero-length label.
++     * If the answer_data is - vm1tst.ovn.org, it will be encoded as
++     *  - 0010 (Total length which is 16)
++     *  - 06766d31747374 (vm1tst)
++     *  - 036f766e (ovn)
++     *  - 036f7267 (org
++     *  - 00 (zero length field) */
++    encoded_answer_length = strlen(answer_data) + 2;
++    encoded_answer = (char *)xzalloc(encoded_answer_length);
++
++    put_be16(dns_answer, htons(encoded_answer_length));
++    uint8_t label_len_index = 0;
++    uint16_t label_len = 0;
++    char *encoded_answer_ptr = (char *)encoded_answer + 1;
++    while (*answer_data) {
++        if (*answer_data == '.') {
++            /* Label has ended.  Update the length of the label. */
++            encoded_answer[label_len_index] = label_len;
++            label_len_index += (label_len + 1);
++            label_len = 0; /* Init to 0 for the next label. */
++        } else {
++            *encoded_answer_ptr =  *answer_data;
++            label_len++;
++        }
++        encoded_answer_ptr++;
++        answer_data++;
++    }
++
++    /* This is required for the last label if it doesn't end with '.' */
++    if (label_len) {
++        encoded_answer[label_len_index] = label_len;
++    }
++
++    ofpbuf_put(dns_answer, encoded_answer, encoded_answer_length);
++    free(encoded_answer);
++}
++
+ /* Called with in the pinctrl_handler thread context. */
+ static void
+ pinctrl_handle_dns_lookup(
+@@ -1753,15 +1853,16 @@ pinctrl_handle_dns_lookup(
+     }
+ 
+     uint16_t query_type = ntohs(*ALIGNED_CAST(const ovs_be16 *, in_dns_data));
+-    /* Supported query types - A, AAAA and ANY */
++    /* Supported query types - A, AAAA, ANY and PTR */
+     if (!(query_type == DNS_QUERY_TYPE_A || query_type == DNS_QUERY_TYPE_AAAA
+-          || query_type == DNS_QUERY_TYPE_ANY)) {
++          || query_type == DNS_QUERY_TYPE_ANY
++          || query_type == DNS_QUERY_TYPE_PTR)) {
+         ds_destroy(&query_name);
+         goto exit;
+     }
+ 
+     uint64_t dp_key = ntohll(pin->flow_metadata.flow.metadata);
+-    const char *answer_ips = NULL;
++    const char *answer_data = NULL;
+     struct shash_node *iter;
+     SHASH_FOR_EACH (iter, &dns_cache) {
+         struct dns_data *d = iter->data;
+@@ -1771,76 +1872,58 @@ pinctrl_handle_dns_lookup(
+                  * lowercase to perform case insensitive lookup
+                  */
+                 char *query_name_lower = str_tolower(ds_cstr(&query_name));
+-                answer_ips = smap_get(&d->records, query_name_lower);
++                answer_data = smap_get(&d->records, query_name_lower);
+                 free(query_name_lower);
+-                if (answer_ips) {
++                if (answer_data) {
+                     break;
+                 }
+             }
+         }
+ 
+-        if (answer_ips) {
++        if (answer_data) {
+             break;
+         }
+     }
+ 
+     ds_destroy(&query_name);
+-    if (!answer_ips) {
++    if (!answer_data) {
+         goto exit;
+     }
+ 
+-    struct lport_addresses ip_addrs;
+-    if (!extract_ip_addresses(answer_ips, &ip_addrs)) {
+-        goto exit;
+-    }
+ 
+     uint16_t ancount = 0;
+     uint64_t dns_ans_stub[128 / 8];
+     struct ofpbuf dns_answer = OFPBUF_STUB_INITIALIZER(dns_ans_stub);
+ 
+-    if (query_type == DNS_QUERY_TYPE_A || query_type == DNS_QUERY_TYPE_ANY) {
+-        for (size_t i = 0; i < ip_addrs.n_ipv4_addrs; i++) {
+-            /* Copy the answer section */
+-            /* Format of the answer section is
+-             *  - NAME     -> The domain name
+-             *  - TYPE     -> 2 octets containing one of the RR type codes
+-             *  - CLASS    -> 2 octets which specify the class of the data
+-             *                in the RDATA field.
+-             *  - TTL      -> 32 bit unsigned int specifying the time
+-             *                interval (in secs) that the resource record
+-             *                 may be cached before it should be discarded.
+-             *  - RDLENGTH -> 16 bit integer specifying the length of the
+-             *                RDATA field.
+-             *  - RDATA    -> a variable length string of octets that
+-             *                describes the resource. In our case it will
+-             *                be IP address of the domain name.
+-             */
+-            ofpbuf_put(&dns_answer, in_queryname, idx);
+-            put_be16(&dns_answer, htons(DNS_QUERY_TYPE_A));
+-            put_be16(&dns_answer, htons(DNS_CLASS_IN));
+-            put_be32(&dns_answer, htonl(DNS_DEFAULT_RR_TTL));
+-            put_be16(&dns_answer, htons(sizeof(ovs_be32)));
+-            put_be32(&dns_answer, ip_addrs.ipv4_addrs[i].addr);
+-            ancount++;
++    if (query_type == DNS_QUERY_TYPE_PTR) {
++        dns_build_ptr_answer(&dns_answer, in_queryname, idx, answer_data);
++        ancount++;
++    } else {
++        struct lport_addresses ip_addrs;
++        if (!extract_ip_addresses(answer_data, &ip_addrs)) {
++            goto exit;
++        }
++
++        if (query_type == DNS_QUERY_TYPE_A ||
++            query_type == DNS_QUERY_TYPE_ANY) {
++            for (size_t i = 0; i < ip_addrs.n_ipv4_addrs; i++) {
++                dns_build_a_answer(&dns_answer, in_queryname, idx,
++                                   ip_addrs.ipv4_addrs[i].addr);
++                ancount++;
++            }
+         }
+-    }
+ 
+-    if (query_type == DNS_QUERY_TYPE_AAAA ||
+-        query_type == DNS_QUERY_TYPE_ANY) {
+-        for (size_t i = 0; i < ip_addrs.n_ipv6_addrs; i++) {
+-            ofpbuf_put(&dns_answer, in_queryname, idx);
+-            put_be16(&dns_answer, htons(DNS_QUERY_TYPE_AAAA));
+-            put_be16(&dns_answer, htons(DNS_CLASS_IN));
+-            put_be32(&dns_answer, htonl(DNS_DEFAULT_RR_TTL));
+-            const struct in6_addr *ip6 = &ip_addrs.ipv6_addrs[i].addr;
+-            put_be16(&dns_answer, htons(sizeof *ip6));
+-            ofpbuf_put(&dns_answer, ip6, sizeof *ip6);
+-            ancount++;
++        if (query_type == DNS_QUERY_TYPE_AAAA ||
++            query_type == DNS_QUERY_TYPE_ANY) {
++            for (size_t i = 0; i < ip_addrs.n_ipv6_addrs; i++) {
++                dns_build_aaaa_answer(&dns_answer, in_queryname, idx,
++                                      &ip_addrs.ipv6_addrs[i].addr);
++                ancount++;
++            }
+         }
++        destroy_lport_addresses(&ip_addrs);
+     }
+ 
+-    destroy_lport_addresses(&ip_addrs);
+-
+     if (!ancount) {
+         ofpbuf_uninit(&dns_answer);
+         goto exit;
+diff --git a/lib/ovn-l7.h b/lib/ovn-l7.h
+index 507949c28..899162866 100644
+--- a/lib/ovn-l7.h
++++ b/lib/ovn-l7.h
+@@ -26,6 +26,14 @@
+ #include "hash.h"
+ #include "ovn/logical-fields.h"
+ 
++#define DNS_QUERY_TYPE_A        0x01
++#define DNS_QUERY_TYPE_AAAA     0x1c
++#define DNS_QUERY_TYPE_ANY      0xff
++#define DNS_QUERY_TYPE_PTR      0x0c
++
++#define DNS_CLASS_IN            0x01
++#define DNS_DEFAULT_RR_TTL      3600
++
+ /* Generic options map which is used to store dhcpv4 opts and dhcpv6 opts. */
+ struct gen_opts_map {
+     struct hmap_node hmap_node;
+diff --git a/ovn-nb.xml b/ovn-nb.xml
+index f30cc9ee9..a57e7498f 100644
+--- a/ovn-nb.xml
++++ b/ovn-nb.xml
+@@ -3188,7 +3188,13 @@
+       Key-value pair of DNS records with <code>DNS query name</code> as the key
+       and value as a string of IP address(es) separated by comma or space.
+ 
++      For PTR requests, the key-value pair can be
++      <code>Reverse IPv4 address.in-addr.arpa</code> and the value
++      <code>DNS domain name</code>.  For IPv6 addresses, the key
++      has to be <code>Reverse IPv6 address.ip6.arpa</code>.
++
+       <p><b>Example: </b> "vm1.ovn.org" = "10.0.0.4 aef0::4"</p>
++      <p><b>Example: </b> "4.0.0.10.in-addr.arpa" = "vm1.ovn.org"</p>
+     </column>
+ 
+     <column name="external_ids">
+diff --git a/tests/ovn.at b/tests/ovn.at
+index b6eff4349..87d0bd4fc 100644
+--- a/tests/ovn.at
++++ b/tests/ovn.at
+@@ -8256,10 +8256,13 @@ ovn-nbctl lsp-set-port-security ls1-lp2 "f0:00:00:00:00:02 10.0.0.6 20.0.0.4"
+ 
+ DNS1=`ovn-nbctl create DNS records={}`
+ DNS2=`ovn-nbctl create DNS records={}`
++DNS3=`ovn-nbctl create DNS records={}`
+ 
+ ovn-nbctl set DNS $DNS1 records:vm1.ovn.org="10.0.0.4 aef0::4"
+ ovn-nbctl set DNS $DNS1 records:vm2.ovn.org="10.0.0.6 20.0.0.4"
+ ovn-nbctl set DNS $DNS2 records:vm3.ovn.org="40.0.0.4"
++ovn-nbctl set DNS $DNS3 records:4.0.0.10.in-addr.arpa="vm1.ovn.org"
++ovn-nbctl set DNS $DNS3 records:4.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.f.e.a.ip6.arpa="vm1.ovn.org"
+ 
+ ovn-nbctl set Logical_switch ls1 dns_records="$DNS1"
+ 
+@@ -8365,6 +8368,21 @@ set_dns_params() {
+     vm1_incomplete)
+         # set type to none
+         type=''
++        ;;
++    vm1_ipv4_ptr)
++        # 4.0.0.10.in-addr.arpa
++        query_name=01340130013002313007696e2d61646472046172706100
++        type=000c
++        # vm1.ovn.org
++        expected_dns_answer=${query_name}${type}0001${ttl}000d03766d31036f766e036f726700
++        ;;
++    vm1_ipv6_ptr)
++        # 4.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.f.e.a.ip6.arpa
++        query_name=0134013001300130013001300130013001300130013001300130013001300130013001300130013001300130013001300130013001300130013001660165016103697036046172706100
++        type=000c
++        # vm1.ovn.org
++        expected_dns_answer=${query_name}${type}0001${ttl}000d03766d31036f766e036f726700
++        ;;
+     esac
+     # TTL - 3600
+     local dns_req_header=010201200001000000000000
+@@ -8464,6 +8482,7 @@ reset_pcap_file hv1-vif2 hv1/vif2
+ rm -f 1.expected
+ rm -f 2.expected
+ 
++
+ set_dns_params vm1
+ src_ip=`ip_to_hex 10 0 0 6`
+ dst_ip=`ip_to_hex 10 0 0 1`
+@@ -8485,8 +8504,8 @@ reset_pcap_file hv1-vif2 hv1/vif2
+ rm -f 1.expected
+ rm -f 2.expected
+ 
+-# Try vm1 again but an all-caps query name
+ 
++# Try vm1 again but an all-caps query name
+ set_dns_params VM1
+ src_ip=`ip_to_hex 10 0 0 6`
+ dst_ip=`ip_to_hex 10 0 0 1`
+@@ -8508,6 +8527,7 @@ reset_pcap_file hv1-vif2 hv1/vif2
+ rm -f 1.expected
+ rm -f 2.expected
+ 
++
+ # Clear the query name options for ls1-lp2
+ ovn-nbctl --wait=hv remove DNS $DNS1 records vm2.ovn.org
+ 
+@@ -8528,6 +8548,7 @@ reset_pcap_file hv1-vif2 hv1/vif2
+ rm -f 1.expected
+ rm -f 2.expected
+ 
++
+ # Clear the query name for ls1-lp1
+ # Since ls1 has no query names configued,
+ # ovn-northd should not add the DNS flows.
+@@ -8550,6 +8571,7 @@ reset_pcap_file hv1-vif2 hv1/vif2
+ rm -f 1.expected
+ rm -f 2.expected
+ 
++
+ # Test IPv6 (AAAA records) using IPv4 packet.
+ # Add back the DNS options for ls1-lp1.
+ ovn-nbctl --wait=hv set DNS $DNS1 records:vm1.ovn.org="10.0.0.4 aef0::4"
+@@ -8575,6 +8597,7 @@ reset_pcap_file hv1-vif2 hv1/vif2
+ rm -f 1.expected
+ rm -f 2.expected
+ 
++
+ # Test both IPv4 (A) and IPv6 (AAAA records) using IPv4 packet.
+ set_dns_params vm1_ipv4_v6
+ src_ip=`ip_to_hex 10 0 0 6`
+@@ -8597,6 +8620,7 @@ reset_pcap_file hv1-vif2 hv1/vif2
+ rm -f 1.expected
+ rm -f 2.expected
+ 
++
+ # Invalid type.
+ set_dns_params vm1_invalid_type
+ src_ip=`ip_to_hex 10 0 0 6`
+@@ -8615,6 +8639,7 @@ reset_pcap_file hv1-vif2 hv1/vif2
+ rm -f 1.expected
+ rm -f 2.expected
+ 
++
+ # Incomplete DNS packet.
+ set_dns_params vm1_incomplete
+ src_ip=`ip_to_hex 10 0 0 6`
+@@ -8633,6 +8658,7 @@ reset_pcap_file hv1-vif2 hv1/vif2
+ rm -f 1.expected
+ rm -f 2.expected
+ 
++
+ # Add one more DNS record to the ls1.
+ ovn-nbctl --wait=hv set Logical_switch ls1 dns_records="$DNS1 $DNS2"
+ 
+@@ -8657,6 +8683,7 @@ reset_pcap_file hv1-vif2 hv1/vif2
+ rm -f 1.expected
+ rm -f 2.expected
+ 
++
+ # Try DNS query over IPv6
+ set_dns_params vm1
+ src_ip=aef00000000000000000000000000004
+@@ -8677,6 +8704,60 @@ reset_pcap_file hv1-vif2 hv1/vif2
+ rm -f 1.expected
+ rm -f 2.expected
+ 
++
++# Add one more DNS record to the ls1.
++ovn-nbctl --wait=hv set Logical_switch ls1 dns_records="$DNS1 $DNS2 $DNS3"
++echo "*************************"
++ovn-sbctl list DNS
++echo "*************************"
++ovn-nbctl list DNS
++echo "*************************"
++
++# Test PTR record for IPv4 address using IPv4 packet.
++set_dns_params vm1_ipv4_ptr
++src_ip=`ip_to_hex 10 0 0 4`
++dst_ip=`ip_to_hex 10 0 0 1`
++dns_reply=1
++test_dns 1 f00000000001 f000000000f0 $src_ip $dst_ip $dns_reply $dns_req_data $dns_resp_data
++
++# NXT_RESUMEs should be 11.
++OVS_WAIT_UNTIL([test 11 = `cat ofctl_monitor*.log | grep -c NXT_RESUME`])
++
++$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])
++
++reset_pcap_file hv1-vif1 hv1/vif1
++reset_pcap_file hv1-vif2 hv1/vif2
++rm -f 1.expected
++rm -f 2.expected
++
++
++# Test PTR record for IPv6 address using IPv4 packet.
++set_dns_params vm1_ipv6_ptr
++src_ip=`ip_to_hex 10 0 0 4`
++dst_ip=`ip_to_hex 10 0 0 1`
++dns_reply=1
++test_dns 1 f00000000001 f000000000f0 $src_ip $dst_ip $dns_reply $dns_req_data $dns_resp_data
++
++# NXT_RESUMEs should be 12.
++OVS_WAIT_UNTIL([test 12 = `cat ofctl_monitor*.log | grep -c NXT_RESUME`])
++
++$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])
++
++reset_pcap_file hv1-vif1 hv1/vif1
++reset_pcap_file hv1-vif2 hv1/vif2
++rm -f 1.expected
++rm -f 2.expected
++
+ OVN_CLEANUP([hv1])
+ 
+ AT_CLEANUP
+-- 
+2.33.1
+
diff --git a/debian/patches/series b/debian/patches/series
index fbe5db9..ba80c08 100644
--- a/debian/patches/series
+++ b/debian/patches/series
@@ -4,3 +4,5 @@ lp-1914988-tests-Use-ovn_start-in-tests-ovn-controller.at.patch
 lp-1914988-tests-Make-certificate-generation-extendable.patch
 lp-1914988-tests-Test-with-SSL-and-RBAC-for-controller-by-defau.patch
 lp-1943266-physical-do-not-forward-traffic-from-localport-to-a-.patch
+lp-1857026-0001-DNS-Make-DNS-lookups-case-insensitive.patch
+lp-1857026-0002-controller-Add-support-for-PTR-DNS-requests.patch