From 3d27384fc5f2a437b7bce128c8ba62e8d6e12df7 Mon Sep 17 00:00:00 2001

From: Brian Haley <haleyb.dev@gmail.com>

Date: Wed, 28 Aug 2019 16:13:23 -0400

Subject: [PATCH] Change dhcp_release to use default address when no IP subnet

 matches

Currently, dhcp_release will only send a 'fake' release

when the address given is in the same subnet as an IP

on the interface that was given.

This doesn't work in an environment where dnsmasq is

managing leases for remote subnets via a DHCP relay, as

running dhcp_release locally will just cause it to

silently exit without doing anything, leaving the lease

in the database.

Change it to use the default IP on the interface, as the

dnsmasq source code at src/dhcp.c does, if no matching subnet

IP is found, as a fall-back.  This fixes an issue we are

seeing in certain Openstack deployments where we are using

dnsmasq to provision baremetal systems in a datacenter.

While using Dbus might have seemed like an obvious solution,

because of our extensive use of network namespaces (which

Dbus doesn't support), this seemed like a better solution

than creating system.d policy files for each dnsmasq we

might spawn and using --enable-dbus=$id in order to isolate

messages to specific dnsmasq instances.

Signed-off-by: Brian Haley <haleyb.dev@gmail.com>

(cherry picked from commit d9f882bea2806799bf3d1f73937f5e72d0bfc650)

---

 contrib/lease-tools/dhcp_release.c | 12 +++++++++---

 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/contrib/lease-tools/dhcp_release.c b/contrib/lease-tools/dhcp_release.c

index a51f04b..1dd8d32 100644

--- a/contrib/lease-tools/dhcp_release.c

+++ b/contrib/lease-tools/dhcp_release.c

@@ -178,7 +178,7 @@ static int is_same_net(struct in_addr a, struct in_addr b, struct in_addr mask)

   return (a.s_addr & mask.s_addr) == (b.s_addr & mask.s_addr);

 }

-static struct in_addr find_interface(struct in_addr client, int fd, unsigned int index)

+static struct in_addr find_interface(struct in_addr client, int fd, unsigned int index, int ifrfd, struct ifreq *ifr)

 {

   struct sockaddr_nl addr;

   struct nlmsghdr *h;

@@ -218,7 +218,13 @@ static struct in_addr find_interface(struct in_addr client, int fd, unsigned int

       for (h = (struct nlmsghdr *)iov.iov_base; NLMSG_OK(h, (size_t)len); h = NLMSG_NEXT(h, len))

 	if (h->nlmsg_type == NLMSG_DONE)

-	  exit(0);

+          {

+	    /* No match found, return first address as src/dhcp.c code does */

+	    ifr->ifr_addr.sa_family = AF_INET;

+	    if (ioctl(ifrfd, SIOCGIFADDR, ifr) != -1)

+	      return ((struct sockaddr_in *)&ifr->ifr_addr)->sin_addr;

+	    exit(0);

+          }

 	else if (h->nlmsg_type == RTM_NEWADDR)

           {

             struct ifaddrmsg *ifa = NLMSG_DATA(h);  

@@ -284,7 +290,7 @@ int main(int argc, char **argv)

     }

   lease.s_addr = inet_addr(argv[2]);

-  server = find_interface(lease, nl, if_nametoindex(argv[1]));

+  server = find_interface(lease, nl, if_nametoindex(argv[1]), fd, &ifr);

   memset(&packet, 0, sizeof(packet));

-- 

2.20.1