diff options
| -rw-r--r-- | conf.c | 25 |
1 files changed, 24 insertions, 1 deletions
@@ -558,6 +558,9 @@ static int conf_ip4_prefix(const char *arg) static unsigned int conf_ip4(unsigned int ifi, struct ip4_ctx *ip4, unsigned char *mac) { + in_addr_t addr, gw; + int shift; + if (!ifi) ifi = nl_get_ext_if(AF_INET); @@ -572,8 +575,10 @@ static unsigned int conf_ip4(unsigned int ifi, if (IN4_IS_ADDR_UNSPECIFIED(&ip4->addr)) nl_addr(0, ifi, AF_INET, &ip4->addr, &ip4->prefix_len, NULL); + addr = ntohl(ip4->addr.s_addr); + gw = ntohl(ip4->gw.s_addr); + if (!ip4->prefix_len) { - in_addr_t addr = ntohl(ip4->addr.s_addr); if (IN_CLASSA(addr)) ip4->prefix_len = (32 - IN_CLASSA_NSHIFT); else if (IN_CLASSB(addr)) @@ -584,6 +589,24 @@ static unsigned int conf_ip4(unsigned int ifi, ip4->prefix_len = 32; } + /* We might get an address with a netmask that makes the default + * gateway unreachable, and in that case we would fail to configure + * the default route, with --config-net, or presumably a DHCP client + * in the guest or container would face the same issue. + * + * The host might have another route, to the default gateway itself, + * fixing the situation, but we only read default routes. + * + * Fix up the mask to allow reaching the default gateway from our + * configured address, if needed, and only if we find a non-zero + * mask that makes the gateway reachable. + */ + shift = 32 - ip4->prefix_len; + while (shift < 32 && addr >> shift != gw >> shift) + shift++; + if (shift < 32) + ip4->prefix_len = 32 - shift; + memcpy(&ip4->addr_seen, &ip4->addr, sizeof(ip4->addr_seen)); if (MAC_IS_ZERO(mac)) |