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Diffstat (limited to 'conf.c')
-rw-r--r--conf.c25
1 files changed, 24 insertions, 1 deletions
diff --git a/conf.c b/conf.c
index f5099a7..b51effc 100644
--- a/conf.c
+++ b/conf.c
@@ -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))