1 files changed, 22 insertions, 16 deletions

diff --git a/networking/zcip.c b/networking/zcip.c
index 7314ff8db..45d1f7c1c 100644
--- a/networking/zcip.c
+++ b/networking/zcip.c
@@ -366,11 +366,11 @@ int zcip_main(int argc UNUSED_PARAM, char **argv)
                                         nprobes++;
                                         VDBG("probe/%u %s@%s\n",
                                                         nprobes, argv_intf, inet_ntoa(ip));
+                                        timeout_ms = PROBE_MIN * 1000;
+                                        timeout_ms += random_delay_ms(PROBE_MAX - PROBE_MIN);
                                         arp(/* ARPOP_REQUEST, */
                                                         /* &eth_addr, */ null_ip,
                                                         &null_addr, ip);
-                                        timeout_ms = PROBE_MIN * 1000;
-                                        timeout_ms += random_delay_ms(PROBE_MAX - PROBE_MIN);
                                 }
                                 else {
                                         // Switch to announce state.
@@ -378,10 +378,10 @@ int zcip_main(int argc UNUSED_PARAM, char **argv)
                                         nclaims = 0;
                                         VDBG("announce/%u %s@%s\n",
                                                         nclaims, argv_intf, inet_ntoa(ip));
+                                        timeout_ms = ANNOUNCE_INTERVAL * 1000;
                                         arp(/* ARPOP_REQUEST, */
                                                         /* &eth_addr, */ ip,
                                                         &eth_addr, ip);
-                                        timeout_ms = ANNOUNCE_INTERVAL * 1000;
                                 }
                                 break;
                         case RATE_LIMIT_PROBE:
@@ -391,10 +391,10 @@ int zcip_main(int argc UNUSED_PARAM, char **argv)
                                 nclaims = 0;
                                 VDBG("announce/%u %s@%s\n",
                                                 nclaims, argv_intf, inet_ntoa(ip));
+                                timeout_ms = ANNOUNCE_INTERVAL * 1000;
                                 arp(/* ARPOP_REQUEST, */
                                                 /* &eth_addr, */ ip,
                                                 &eth_addr, ip);
-                                timeout_ms = ANNOUNCE_INTERVAL * 1000;
                                 break;
                         case ANNOUNCE:
                                 // timeouts in the ANNOUNCE state mean no conflicting ARP packets
@@ -403,10 +403,10 @@ int zcip_main(int argc UNUSED_PARAM, char **argv)
                                         nclaims++;
                                         VDBG("announce/%u %s@%s\n",
                                                         nclaims, argv_intf, inet_ntoa(ip));
+                                        timeout_ms = ANNOUNCE_INTERVAL * 1000;
                                         arp(/* ARPOP_REQUEST, */
                                                         /* &eth_addr, */ ip,
                                                         &eth_addr, ip);
-                                        timeout_ms = ANNOUNCE_INTERVAL * 1000;
                                 }
                                 else {
                                         // Switch to monitor state.
@@ -495,22 +495,28 @@ int zcip_main(int argc UNUSED_PARAM, char **argv)
                         }
 #endif
                         if (p.arp.arp_op != htons(ARPOP_REQUEST)
-                         && p.arp.arp_op != htons(ARPOP_REPLY))
+                         && p.arp.arp_op != htons(ARPOP_REPLY)
+                        ) {
                                 continue;
+                        }
 
                         source_ip_conflict = 0;
                         target_ip_conflict = 0;
 
-                        if (memcmp(p.arp.arp_spa, &ip.s_addr, sizeof(struct in_addr)) == 0
-                         && memcmp(&p.arp.arp_sha, &eth_addr, ETH_ALEN) != 0
-                        ) {
-                                source_ip_conflict = 1;
-                        }
-                        if (p.arp.arp_op == htons(ARPOP_REQUEST)
-                         && memcmp(p.arp.arp_tpa, &ip.s_addr, sizeof(struct in_addr)) == 0
-                         && memcmp(&p.arp.arp_tha, &eth_addr, ETH_ALEN) != 0
-                        ) {
-                                target_ip_conflict = 1;
+                        if (memcmp(&p.arp.arp_sha, &eth_addr, ETH_ALEN) != 0) {
+                                if (memcmp(p.arp.arp_spa, &ip.s_addr, sizeof(struct in_addr))) {
+                                        /* A probe or reply with source_ip == chosen ip */
+                                        source_ip_conflict = 1;
+                                }
+                                if (p.arp.arp_op == htons(ARPOP_REQUEST)
+                                 && memcmp(p.arp.arp_spa, &null_ip, sizeof(struct in_addr)) == 0
+                                 && memcmp(p.arp.arp_tpa, &ip.s_addr, sizeof(struct in_addr)) == 0
+                                ) {
+                                        /* A probe with source_ip == 0.0.0.0, target_ip == chosen ip:
+                                         * another host trying to claim this ip!
+                                         */
+                                        target_ip_conflict = 1;
+                                }
                         }
 
                         VDBG("state = %d, source ip conflict = %d, target ip conflict = %d\n",