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--dhcp-reply-delay option to workaround PXE client bugs.

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Adds option to delay replying to DHCP packets by one or more seconds.
This provides a workaround for a PXE boot firmware implementation
that has a bug causing it to fail if it receives a (proxy) DHCP
reply instantly.

On Linux it looks up the exact receive time of the UDP packet with
the SIOCGSTAMP ioctl to prevent multiple delays if multiple packets
come in around the same time.
This commit is contained in:
Floris Bos
2017-04-09 23:07:13 +01:00
committed by Simon Kelley
parent 60704f5e2e
commit 503c609149
8 changed files with 158 additions and 57 deletions
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9
src/dhcp.c
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@@ -149,8 +149,10 @@ void dhcp_packet(time_t now, int pxe_fd)
int rcvd_iface_index;
struct in_addr iface_addr;
struct iface_param parm;
time_t recvtime = now;
#ifdef HAVE_LINUX_NETWORK
struct arpreq arp_req;
struct timeval tv;
#endif
union {
@@ -177,6 +179,9 @@ void dhcp_packet(time_t now, int pxe_fd)
return;
#if defined (HAVE_LINUX_NETWORK)
if (ioctl(fd, SIOCGSTAMP, &tv) == 0)
recvtime = tv.tv_sec;
if (msg.msg_controllen >= sizeof(struct cmsghdr))
for (cmptr = CMSG_FIRSTHDR(&msg); cmptr; cmptr = CMSG_NXTHDR(&msg, cmptr))
if (cmptr->cmsg_level == IPPROTO_IP && cmptr->cmsg_type == IP_PKTINFO)
@@ -335,14 +340,14 @@ void dhcp_packet(time_t now, int pxe_fd)
lease_prune(NULL, now); /* lose any expired leases */
iov.iov_len = dhcp_reply(parm.current, ifr.ifr_name, iface_index, (size_t)sz,
now, unicast_dest, &is_inform, pxe_fd, iface_addr);
now, unicast_dest, &is_inform, pxe_fd, iface_addr, recvtime);
lease_update_file(now);
lease_update_dns(0);
if (iov.iov_len == 0)
return;
}
msg.msg_name = &dest;
msg.msg_namelen = sizeof(dest);
msg.msg_control = NULL;