diff options
| -rw-r--r-- | src/dhcpv4.c | 74 |
1 files changed, 49 insertions, 25 deletions
diff --git a/src/dhcpv4.c b/src/dhcpv4.c index 1807c68..462f641 100644 --- a/src/dhcpv4.c +++ b/src/dhcpv4.c @@ -502,50 +502,74 @@ static void handle_dhcpv4(void *addr, void *data, size_t len, (struct sockaddr*)&dest, sizeof(dest)); } +static bool dhcpv4_test(struct interface *iface, uint32_t try) +{ + struct dhcpv4_assignment *c; + list_for_each_entry(c, &iface->dhcpv4_assignments, head) { + if (c->addr == try) { + return false; + } + } + return true; +} static bool dhcpv4_assign(struct interface *iface, struct dhcpv4_assignment *assign, uint32_t raddr) { - const unsigned tries = 100; uint32_t start = ntohl(iface->dhcpv4_start.s_addr); uint32_t end = ntohl(iface->dhcpv4_end.s_addr); uint32_t count = end - start + 1; + // try to assign the IP the client asked for + if (start <= raddr && raddr <= end && dhcpv4_test(iface, raddr)) { + assign->addr = raddr; + list_add(&assign->head, &iface->dhcpv4_assignments); + syslog(LOG_DEBUG, "assigning the IP the client asked for: %u.%u.%u.%u", + (assign->addr & 0xff000000) >> 24, + (assign->addr & 0x00ff0000) >> 16, + (assign->addr & 0x0000ff00) >> 8, + (assign->addr & 0x000000ff)); + return true; + } + // Seed RNG with checksum of hwaddress uint32_t seed = 0; - for (size_t i = 0; i < sizeof(assign->hwaddr); ++i) - seed += assign->hwaddr[i]; + for (size_t i = 0; i < sizeof(assign->hwaddr); ++i) { + // Knuth's multiplicative method + uint8_t o = assign->hwaddr[i]; + seed += (o*2654435761) % UINT32_MAX; + } srand(seed); - // Try to assign up to 100x - for (unsigned i = 0; i < tries; ++i) { - uint32_t try = (((uint32_t)rand()) % count) + start; - if (i == 0 && raddr >= start && raddr <= end) - try = raddr; - else if (i == tries - 1) - try = start; + uint32_t try = (((uint32_t)rand()) % count) + start; + + if (list_empty(&iface->dhcpv4_assignments)) { + assign->addr = try; + list_add(&assign->head, &iface->dhcpv4_assignments); + syslog(LOG_DEBUG, "assigning mapped IP (empty list): %u.%u.%u.%u", + (assign->addr & 0xff000000) >> 24, + (assign->addr & 0x00ff0000) >> 16, + (assign->addr & 0x0000ff00) >> 8, + (assign->addr & 0x000000ff)); + return true; + } - if (list_empty(&iface->dhcpv4_assignments)) { + for (size_t i = 0; i < count; ++i) { + if (dhcpv4_test(iface, try)) { + /* test was successful: IP address is not assigned, assign it */ assign->addr = try; list_add(&assign->head, &iface->dhcpv4_assignments); + syslog(LOG_DEBUG, "assigning mapped IP: %u.%u.%u.%u (try %d of %d)", + (assign->addr & 0xff000000) >> 24, + (assign->addr & 0x00ff0000) >> 16, + (assign->addr & 0x0000ff00) >> 8, + (assign->addr & 0x000000ff), i, count); return true; } - - struct dhcpv4_assignment *c; - list_for_each_entry(c, &iface->dhcpv4_assignments, head) { - if (c->addr > try) { - assign->addr = try; - list_add_tail(&assign->head, &c->head); - return true; - } else if (c->addr == try) { - if (i < tries - 1) - break; - else - ++try; - } - } + try = (((try - start) + 1) % count) + start; } + syslog(LOG_DEBUG, "can't assign any IP address -> address space is full"); return false; } |