dhcpv4: dhcpv4_assign() - explain address assignment

Add some debug statements that also serve as comments explaining the logic
of dhcpv4_assign() and which make it easier to understand why a
requested address was not provided.

Signed-off-by: David Härdeman <[email protected]>
Link: https://github.com/openwrt/odhcpd/pull/286
Signed-off-by: Álvaro Fernández Rojas <[email protected]>

diff --git a/src/dhcpv4.c b/src/dhcpv4.c
index 3fc1a3dd87ff59271d47fabb02da505b266ac93c..173457a80e85243eda7937c7fd1c450a3f2feaa8 100644 (file)
--- a/src/dhcpv4.c
+++ b/src/dhcpv4.c
@@ -367,43 +367,48 @@ static bool dhcpv4_assign(struct interface *iface, struct dhcp_assignment *a,
        uint32_t end = ntohl(iface->dhcpv4_end_ip.s_addr);
        uint32_t count = end - start + 1;
        uint32_t seed = 0;
-       bool assigned;
        char ipv4_str[INET_ADDRSTRLEN];
 
        /* Preconfigured IP address by static lease */
        if (a->addr) {
-               assigned = dhcpv4_insert_assignment(&iface->dhcpv4_assignments,
-                                                   a, a->addr);
-
-               if (assigned)
-                       debug("Assigning static IP: %s",
+               if (!dhcpv4_insert_assignment(&iface->dhcpv4_assignments, a, a->addr)) {
+                       error("The static IP address is already assigned: %s",
                              inet_ntop(AF_INET, &a->addr, ipv4_str, sizeof(ipv4_str)));
+                       return false;
+               }
 
-               return assigned;
+               debug("Assigned static IP address: %s",
+                     inet_ntop(AF_INET, &a->addr, ipv4_str, sizeof(ipv4_str)));
+               return true;
        }
 
-       /* try to assign the IP the client asked for */
-       if (start <= ntohl(raddr) && ntohl(raddr) <= end &&
-           !config_find_lease_by_ipaddr(raddr)) {
-               assigned = dhcpv4_insert_assignment(&iface->dhcpv4_assignments,
-                                                   a, raddr);
-
-               if (assigned) {
-                       debug("Assigning the IP the client asked for: %s",
-                             inet_ntop(AF_INET, &a->addr, ipv4_str, sizeof(ipv4_str)));
-                       return true;
-               }
+       /* The client asked for a specific address, let's try... */
+       if (ntohl(raddr) < start || ntohl(raddr) > end) {
+               debug("The requested IP address is outside the pool: %s",
+                     inet_ntop(AF_INET, &raddr, ipv4_str, sizeof(ipv4_str)));
+       } else if (config_find_lease_by_ipaddr(raddr)) {
+               debug("The requested IP address is statically assigned: %s",
+                     inet_ntop(AF_INET, &raddr, ipv4_str, sizeof(ipv4_str)));
+       } else if (!dhcpv4_insert_assignment(&iface->dhcpv4_assignments, a, raddr)) {
+               debug("The requested IP address is already assigned: %s",
+                     inet_ntop(AF_INET, &raddr, ipv4_str, sizeof(ipv4_str)));
+       } else {
+               debug("Assigned the requested IP address: %s",
+                     inet_ntop(AF_INET, &a->addr, ipv4_str, sizeof(ipv4_str)));
+               return true;
        }
 
-       /* Seed RNG with checksum of hwaddress */
+       /* Ok, we'll have to pick an address for the client... */
        for (size_t i = 0; i < sizeof(a->hwaddr); ++i) {
-               /* Knuth's multiplicative method */
+               /* ...hash the hwaddr (Knuth's multiplicative method)... */
                uint8_t o = a->hwaddr[i];
-               seed += (o*2654435761) % UINT32_MAX;
+               seed += (o * 2654435761) % UINT32_MAX;
        }
 
+       /* ...use it to seed the RNG... */
        srand(seed);
 
+       /* ...and try a bunch of times to assign a randomly chosen address */
        for (uint32_t i = 0, try = (((uint32_t)rand()) % count) + start; i < count;
             ++i, try = (((try - start) + 1) % count) + start) {
                uint32_t n_try = htonl(try);
@@ -411,14 +416,10 @@ static bool dhcpv4_assign(struct interface *iface, struct dhcp_assignment *a,
                if (config_find_lease_by_ipaddr(n_try))
                        continue;
 
-               assigned = dhcpv4_insert_assignment(&iface->dhcpv4_assignments,
-                                                   a, n_try);
-
-               if (assigned) {
-                       debug("Assigning mapped IP: %s (try %u of %u)",
+               if (dhcpv4_insert_assignment(&iface->dhcpv4_assignments, a, n_try)) {
+                       debug("Assigned IP adress from pool: %s (succeeded on attempt %u of %u)",
                              inet_ntop(AF_INET, &a->addr, ipv4_str, sizeof(ipv4_str)),
                              i + 1, count);
-
                        return true;
                }
        }