[ovs-dev] [PATCH v4 2/2 ovn] Add support for DHCP domain search option (119)

Ankur Sharma svc.mail.git at nutanix.com
Mon Jun 1 18:15:25 UTC 2020


From: Dhathri Purohith <dhathri.purohith at nutanix.com>

Domain search list is encoded according to the specifications in RFC 1035,
section 4.1.4.

Signed-off-by: Dhathri Purohith <dhathri.purohith at nutanix.com>
Signed-off-by: Ankur Sharma <ankur.sharma at nutanix.com>
---
 lib/actions.c       | 100 +++++++++++++++++++++++++++++++++++++++++++++++++++-
 lib/ovn-l7.h        |   3 ++
 northd/ovn-northd.c |   1 +
 ovn-sb.ovsschema    |   6 ++--
 ovn-sb.xml          |  11 ++++++
 tests/ovn.at        |   3 ++
 tests/test-ovn.c    |   1 +
 7 files changed, 121 insertions(+), 4 deletions(-)

diff --git a/lib/actions.c b/lib/actions.c
index f21be6d..8f5ed61 100644
--- a/lib/actions.c
+++ b/lib/actions.c
@@ -1982,7 +1982,8 @@ parse_gen_opt(struct action_context *ctx, struct ovnact_gen_option *o,
         return;
     }
 
-    if (!strcmp(o->option->type, "str")) {
+    if (!strcmp(o->option->type, "str") ||
+        !strcmp(o->option->type, "domains")) {
         if (o->value.type != EXPR_C_STRING) {
             lexer_error(ctx->lexer, "%s option %s requires string value.",
                         opts_type, o->option->name);
@@ -2317,6 +2318,103 @@ encode_put_dhcpv4_option(const struct ovnact_gen_option *o,
            opt_header[1] = sizeof(ovs_be32);
            ofpbuf_put(ofpacts, &c->value.ipv4, sizeof(ovs_be32));
         }
+    } else if (!strcmp(o->option->type, "domains")) {
+        /* Please refer to RFC 1035, section 4.1.4 for the format of encoding
+         * domain names. Below is an example for encoding a search list
+         * consisting of the "abc.com" and "xyz.abc.com".
+         *
+         * +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
+         * |119|14 | 3 |'a'|'b'|'c'| 3 |'c'|'o'|'m'| 0 |'x'|'y'|'z'|xC0|x00|
+         * +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
+         *
+         * The encoding of "abc.com" ends with 0 to mark the end of the
+         * domain name as required by RFC 1035.
+         *
+         * The encoding of "xyz" (for "xyz.abc.com") ends with the two-octet
+         * compression pointer C000 (hex), which points to offset 0 where
+         * another validly encoded domain name can be found to complete
+         * the name ("abc.com").
+         */
+        typedef struct namemap_node {
+            struct hmap_node node;
+            uint16_t offset;
+            char *name;
+        } namemap_node;
+        struct hmap namemap;
+        hmap_init(&namemap);
+        namemap_node *ref;
+        /* Encoding adds 2 bytes (one for length and one for delimiter) for
+         * every domain name that is unique. If all the domain names are unique
+         * (which probably never happens in real world), then encoded string
+         * could be longer than the original string. Just to be on the safer
+         * side, allocate the (approx.) worst case length here.
+         */
+        uint8_t *dns_encoded = xzalloc(2 * strlen(c->string));
+        uint8_t encode_offset = 0;
+        char *domain_list = xstrdup(c->string), *dom_ptr = NULL;
+        for (char *domain = strtok_r(domain_list, ",", &dom_ptr);
+             domain != NULL;
+             domain = strtok_r(NULL, ",", &dom_ptr)) {
+            if (strlen(domain) > DOMAIN_NAME_MAX_LEN) {
+                VLOG_WARN("Domain names longer than 255 characters are not"
+                          "supported");
+                goto out;
+            }
+            char *label_ptr = NULL, *label;
+            for (label = strtok_r(domain, ".", &label_ptr);
+                 label != NULL;
+                 label = strtok_r(NULL, ".", &label_ptr)) {
+                ref = NULL;
+                /* Check if we have already encoded this label and
+                 * fill in the reference, if yes. */
+                uint32_t label_hash = hash_string(label, 0);
+                HMAP_FOR_EACH_IN_BUCKET (ref, node, label_hash, &namemap) {
+                    if (!strcmp(label, ref->name)) {
+                        ovs_be16 temp = htons(0xc000) | htons(ref->offset);
+                        memcpy(dns_encoded + encode_offset, &temp,
+                               sizeof(temp));
+                        encode_offset += sizeof(temp);
+                        break;
+                    }
+                }
+                /* Break, since we have already filled the offset for this
+                 * domain. */
+                if (ref != NULL) {
+                    break;
+                } else {
+                    /* The label was not encoded before, encode it now and add
+                     * the offset to the namemap map. */
+                    ref = xzalloc(sizeof *ref);
+                    ref->name = xstrdup(label);
+                    ref->offset = encode_offset;
+                    hmap_insert(&namemap, &ref->node, label_hash);
+
+                    uint8_t len = strlen(label);
+                    memcpy(dns_encoded + encode_offset, &len, sizeof(uint8_t));
+                    encode_offset += sizeof(uint8_t);
+                    memcpy(dns_encoded + encode_offset, label, len);
+                    encode_offset += len;
+                }
+            }
+            /* Add the end marker (0 byte) to determine the end of the
+             * domain. */
+            if (label == NULL) {
+                uint8_t end = 0;
+                memcpy(dns_encoded + encode_offset, &end, sizeof(uint8_t));
+                encode_offset += sizeof(uint8_t);
+            }
+        }
+        opt_header[1] = encode_offset;
+        ofpbuf_put(ofpacts, dns_encoded, encode_offset);
+
+        out:
+            HMAP_FOR_EACH_POP (ref, node, &namemap) {
+                free(ref->name);
+                free(ref);
+            }
+            hmap_destroy(&namemap);
+            free(domain_list);
+            free(dns_encoded);
     }
 }
 
diff --git a/lib/ovn-l7.h b/lib/ovn-l7.h
index 38555db..f34bc0d 100644
--- a/lib/ovn-l7.h
+++ b/lib/ovn-l7.h
@@ -34,6 +34,7 @@ struct gen_opts_map {
     size_t code;
 };
 
+#define DOMAIN_NAME_MAX_LEN 255
 #define DHCP_BROADCAST_FLAG 0x8000
 
 #define DHCP_OPTION(NAME, CODE, TYPE) \
@@ -81,6 +82,8 @@ struct gen_opts_map {
 #define DHCP_OPT_PATH_PREFIX DHCP_OPTION("path_prefix", 210, "str")
 #define DHCP_OPT_TFTP_SERVER_ADDRESS \
     DHCP_OPTION("tftp_server_address", 150, "ipv4")
+#define DHCP_OPT_DOMAIN_SEARCH_LIST \
+    DHCP_OPTION("domain_search_list", 119, "domains")
 
 #define DHCP_OPT_ARP_CACHE_TIMEOUT \
     DHCP_OPTION("arp_cache_timeout", 35, "uint32")
diff --git a/northd/ovn-northd.c b/northd/ovn-northd.c
index ef08414..4ec2034 100644
--- a/northd/ovn-northd.c
+++ b/northd/ovn-northd.c
@@ -11336,6 +11336,7 @@ static struct gen_opts_map supported_dhcp_opts[] = {
     DHCP_OPT_DOMAIN_NAME,
     DHCP_OPT_ARP_CACHE_TIMEOUT,
     DHCP_OPT_TCP_KEEPALIVE_INTERVAL,
+    DHCP_OPT_DOMAIN_SEARCH_LIST,
 };
 
 static struct gen_opts_map supported_dhcpv6_opts[] = {
diff --git a/ovn-sb.ovsschema b/ovn-sb.ovsschema
index 2ec729b..99c5de8 100644
--- a/ovn-sb.ovsschema
+++ b/ovn-sb.ovsschema
@@ -1,7 +1,7 @@
 {
     "name": "OVN_Southbound",
-    "version": "2.8.1",
-    "cksum": "236203406 21905",
+    "version": "2.8.2",
+    "cksum": "464326363 21916",
     "tables": {
         "SB_Global": {
             "columns": {
@@ -218,7 +218,7 @@
                         "type": "string",
                         "enum": ["set", ["bool", "uint8", "uint16", "uint32",
                                          "ipv4", "static_routes", "str",
-                                         "host_id"]]}}}},
+                                         "host_id", "domains"]]}}}},
             "isRoot": true},
         "DHCPv6_Options": {
             "columns": {
diff --git a/ovn-sb.xml b/ovn-sb.xml
index 208fb93..a6da80b 100644
--- a/ovn-sb.xml
+++ b/ovn-sb.xml
@@ -3232,6 +3232,17 @@ tcp.flags = RST;
           </p>
         </dd>
 
+        <dt><code>value: domains</code></dt>
+        <dd>
+          <p>
+            This indicates that the value of the DHCP option is a domain name
+            or a comma separated list of domain names.
+          </p>
+
+          <p>
+            Example. "name=domain_search_list", "code=119", "type=domains".
+          </p>
+        </dd>
       </dl>
     </column>
   </table>
diff --git a/tests/ovn.at b/tests/ovn.at
index fa2592c..91ec564 100644
--- a/tests/ovn.at
+++ b/tests/ovn.at
@@ -1218,6 +1218,9 @@ reg0[15] = put_dhcp_opts(offerip=10.0.0.4,router=10.0.0.1,netmask=255.255.255.0,
 reg0[15] = put_dhcp_opts(offerip=10.0.0.4,router=10.0.0.1,netmask=255.255.255.0,mtu=1400,ip_forward_enable=1,default_ttl=121,dns_server={8.8.8.8,7.7.7.7},classless_static_route={30.0.0.0/24,10.0.0.4,40.0.0.0/16,10.0.0.6,0.0.0.0/0,10.0.0.1},ethernet_encap=1,router_discovery=0,tftp_server="tftp_server_test");
     formats as reg0[15] = put_dhcp_opts(offerip = 10.0.0.4, router = 10.0.0.1, netmask = 255.255.255.0, mtu = 1400, ip_forward_enable = 1, default_ttl = 121, dns_server = {8.8.8.8, 7.7.7.7}, classless_static_route = {30.0.0.0/24, 10.0.0.4, 40.0.0.0/16, 10.0.0.6, 0.0.0.0/0, 10.0.0.1}, ethernet_encap = 1, router_discovery = 0, tftp_server = "tftp_server_test");
     encodes as controller(userdata=00.00.00.02.00.00.00.00.00.01.de.10.00.00.00.6f.0a.00.00.04.03.04.0a.00.00.01.01.04.ff.ff.ff.00.1a.02.05.78.13.01.01.17.01.79.06.08.08.08.08.08.07.07.07.07.79.14.18.1e.00.00.0a.00.00.04.10.28.00.0a.00.00.06.00.0a.00.00.01.24.01.01.1f.01.00.42.10.74.66.74.70.5f.73.65.72.76.65.72.5f.74.65.73.74,pause)
+reg2[5] = put_dhcp_opts(offerip=10.0.0.4,router=10.0.0.1,netmask=255.255.254.0,mtu=1400,domain_name="ovn.org",wpad="https://example.org",bootfile_name="https://127.0.0.1/boot.ipxe",path_prefix="/tftpboot",domain_search_list="ovn.org,abc.ovn.org");
+    formats as reg2[5] = put_dhcp_opts(offerip = 10.0.0.4, router = 10.0.0.1, netmask = 255.255.254.0, mtu = 1400, domain_name = "ovn.org", wpad = "https://example.org", bootfile_name = "https://127.0.0.1/boot.ipxe", path_prefix = "/tftpboot", domain_search_list = "ovn.org,abc.ovn.org");
+    encodes as controller(userdata=00.00.00.02.00.00.00.00.00.01.de.10.00.00.00.25.0a.00.00.04.03.04.0a.00.00.01.01.04.ff.ff.fe.00.1a.02.05.78.0f.07.6f.76.6e.2e.6f.72.67.fc.13.68.74.74.70.73.3a.2f.2f.65.78.61.6d.70.6c.65.2e.6f.72.67.43.1b.68.74.74.70.73.3a.2f.2f.31.32.37.2e.30.2e.30.2e.31.2f.62.6f.6f.74.2e.69.70.78.65.d2.09.2f.74.66.74.70.62.6f.6f.74.77.0f.03.6f.76.6e.03.6f.72.67.00.03.61.62.63.c0.00,pause)
 
 reg1[0..1] = put_dhcp_opts(offerip = 1.2.3.4, router = 10.0.0.1);
     Cannot use 2-bit field reg1[0..1] where 1-bit field is required.
diff --git a/tests/test-ovn.c b/tests/test-ovn.c
index 4391694..b43f67f 100644
--- a/tests/test-ovn.c
+++ b/tests/test-ovn.c
@@ -189,6 +189,7 @@ create_gen_opts(struct hmap *dhcp_opts, struct hmap *dhcpv6_opts,
     dhcp_opt_add(dhcp_opts, "tftp_server_address", 150, "ipv4");
     dhcp_opt_add(dhcp_opts, "arp_cache_timeout", 35, "uint32");
     dhcp_opt_add(dhcp_opts, "tcp_keepalive_interval", 38, "uint32");
+    dhcp_opt_add(dhcp_opts, "domain_search_list", 119, "domains");
 
     /* DHCPv6 options. */
     hmap_init(dhcpv6_opts);
-- 
1.8.3.1



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