dhcpv6: avoid sending continuous renew/rebind messages

If any of the IAs is not present in the Reply message in response
to a Renew/Rebind message don't set t1 to one second.
This will cause a continuous sending of Renew messages every second
if the DHCP server does not include all IAs in the Reply message.
Instead continue the normal retransmission time as if the Reply
message is not received as specified in RFC8415 §18.2.10.1

Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>

diff --git a/src/dhcpv6.c b/src/dhcpv6.c
index d45d86a46582f82485c4d2ec442635ea088abdbc..63eb0ebe2d011730ccd3b05d74061db55b7ef921 100644 (file)
--- a/src/dhcpv6.c
+++ b/src/dhcpv6.c
@@ -61,7 +61,7 @@ static bool dhcpv6_response_is_valid(const void *buf, ssize_t len,
 
 static unsigned int dhcpv6_parse_ia(void *opt, void *end);
 
-static int dhcpv6_calc_refresh_timers(void);
+static unsigned int dhcpv6_calc_refresh_timers(void);
 static void dhcpv6_handle_status_code(_unused const enum dhcpv6_msg orig,
                const uint16_t code, const void *status_msg, const int len,
                int *ret);
@@ -995,6 +995,7 @@ static int dhcpv6_handle_reply(enum dhcpv6_msg orig, _unused const int rc,
        uint16_t otype, olen;
        uint32_t refresh = 86400;
        int ret = 1;
+       unsigned int state_IAs;
        unsigned int updated_IAs = 0;
        bool handled_status_codes[_DHCPV6_Status_Max] = { false, };
 
@@ -1180,55 +1181,83 @@ static int dhcpv6_handle_reply(enum dhcpv6_msg orig, _unused const int rc,
                }
        }
 
+       // Bail out if fatal status code was received
+       if (ret <= 0)
+               return ret;
+
        switch (orig) {
        case DHCPV6_MSG_REQUEST:
        case DHCPV6_MSG_REBIND:
        case DHCPV6_MSG_RENEW:
-               // Update refresh timers if no fatal status code was received
-               if ((ret > 0) && (ret = dhcpv6_calc_refresh_timers())) {
-                       if (orig == DHCPV6_MSG_REQUEST) {
-                               // All server candidates can be cleared if not yet bound
-                               if (!odhcp6c_is_bound())
-                                       dhcpv6_clear_all_server_cand();
-
-                               odhcp6c_clear_state(STATE_SERVER_ADDR);
-                               odhcp6c_add_state(STATE_SERVER_ADDR, &from->sin6_addr, 16);
-                       } else if (orig == DHCPV6_MSG_RENEW) {
-                               // Send further renews if T1 is not set and
-                               // no updated IAs
-                               if (!t1) {
-                                       if (!updated_IAs)
-                                               ret = -1;
-                                       else if ((t2 - t1) > 1)
-                                               // Grace period of 1 second
-                                               t1 = 1;
-                               }
+               state_IAs = dhcpv6_calc_refresh_timers();
+               // In case there're no state IA entries
+               // keep sending request/renew/rebind messages
+               if (state_IAs == 0) {
+                       ret = 0;
+                       break;
+               }
 
-                       } else if (orig == DHCPV6_MSG_REBIND) {
-                               // Send further rebinds if T1 and T2 is not set and
-                               // no updated IAs
-                               if (!t1 && !t2) {
-                                       if (!updated_IAs)
-                                               ret = -1;
-                                       else if ((t3 - t2) > 1)
-                                               // Grace period of 1 second
-                                               t2 = 1;
-                               }
+               if (orig == DHCPV6_MSG_REQUEST) {
+                       // All server candidates can be cleared if not yet bound
+                       if (!odhcp6c_is_bound())
+                               dhcpv6_clear_all_server_cand();
 
-                               odhcp6c_clear_state(STATE_SERVER_ADDR);
-                               odhcp6c_add_state(STATE_SERVER_ADDR, &from->sin6_addr, 16);
+                       odhcp6c_clear_state(STATE_SERVER_ADDR);
+                       odhcp6c_add_state(STATE_SERVER_ADDR, &from->sin6_addr, 16);
+               } else if (orig == DHCPV6_MSG_RENEW) {
+                       // Send further renews if T1 is not set and if
+                       // there're IAs which were not in the Reply message
+                       if (!t1 && state_IAs != updated_IAs) {
+                               if (updated_IAs)
+                                       // Publish updates
+                                       script_call("updated", 0, false);
+
+                               /*
+                                * RFC8415 states following in §18.2.10.1 :
+                                * Sends a Renew/Rebind if any of the IAs are not in the Reply
+                                * message, but as this likely indicates that the server that
+                                * responded does not support that IA type, sending immediately is
+                                * unlikely to produce a different result.  Therefore, the client
+                                * MUST rate-limit its transmissions (see Section 14.1) and MAY just
+                                * wait for the normal retransmission time (as if the Reply message
+                                * had not been received).  The client continues to use other
+                                * bindings for which the server did return information
+                                */
+                               ret = -1;
+                       }
+               } else if (orig == DHCPV6_MSG_REBIND) {
+                       odhcp6c_clear_state(STATE_SERVER_ADDR);
+                       odhcp6c_add_state(STATE_SERVER_ADDR, &from->sin6_addr, 16);
+
+                       // Send further rebinds if T1 and T2 is not set and if
+                       // there're IAs which were not in the Reply message
+                       if (!t1 && !t2 && state_IAs != updated_IAs) {
+                               if (updated_IAs)
+                                       // Publish updates
+                                       script_call("updated", 0, false);
+
+                               /*
+                                * RFC8415 states following in §18.2.10.1 :
+                                * Sends a Renew/Rebind if any of the IAs are not in the Reply
+                                * message, but as this likely indicates that the server that
+                                * responded does not support that IA type, sending immediately is
+                                * unlikely to produce a different result.  Therefore, the client
+                                * MUST rate-limit its transmissions (see Section 14.1) and MAY just
+                                * wait for the normal retransmission time (as if the Reply message
+                                * had not been received).  The client continues to use other
+                                * bindings for which the server did return information
+                                */
+                               ret = -1;
                        }
                }
                break;
 
        case DHCPV6_MSG_INFO_REQ:
-               if (ret > 0) {
-                       // All server candidates can be cleared if not yet bound
-                       if (!odhcp6c_is_bound())
-                               dhcpv6_clear_all_server_cand();
+               // All server candidates can be cleared if not yet bound
+               if (!odhcp6c_is_bound())
+                       dhcpv6_clear_all_server_cand();
 
-                       t1 = refresh;
-               }
+               t1 = refresh;
                break;
 
        default:
@@ -1361,7 +1390,7 @@ static unsigned int dhcpv6_parse_ia(void *opt, void *end)
        return updated_IAs;
 }
 
-static int dhcpv6_calc_refresh_timers(void)
+static unsigned int dhcpv6_calc_refresh_timers(void)
 {
        struct odhcp6c_entry *e;
        size_t ia_na_entries, ia_pd_entries, i;
@@ -1403,7 +1432,7 @@ static int dhcpv6_calc_refresh_timers(void)
                syslog(LOG_INFO, "T1 %"PRId64"s, T2 %"PRId64"s, T3 %"PRId64"s", t1, t2, t3);
        }
 
-       return (int)(ia_pd_entries + ia_na_entries);
+       return (unsigned int)(ia_pd_entries + ia_na_entries);
 }
 
 static void dhcpv6_log_status_code(const uint16_t code, const char *scope,