dhcp, dhcpv6: Add hostname and client fqdn ops

Both DHCPv4 and DHCPv6 has the capability to pass the hostname to
clients, the DHCPv4 uses option 12 (hostname) while the DHCPv6 uses option 39
(client fqdn), for some virt deployments like kubevirt is expected to
have the VirtualMachine name as the guest hostname.

This change add the following arguments:
 - -H --hostname NAME to configure the hostname DHCPv4 option(12)
 - --fqdn NAME to configure client fqdn option for both DHCPv4(81) and
   DHCPv6(39)

Signed-off-by: Enrique Llorente <ellorent@redhat.com>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/util.c b/util.c
index 4d51e04..ba33866 100644
--- a/util.c
+++ b/util.c
@@ -930,4 +930,28 @@ void raw_random(void *buf, size_t buflen)
 void epoll_del(const struct ctx *c, int fd)
 {
 	epoll_ctl(c->epollfd, EPOLL_CTL_DEL, fd, NULL);
+
+}
+
+/**
+ * encode_domain_name() - Encode domain name according to RFC 1035, section 3.1
+ * @buf:		Buffer to fill in with encoded domain name
+ * @domain_name:	Input domain name string with terminator
+ *
+ * The buffer's 'buf' size has to be >= strlen(domain_name) + 2
+ */
+void encode_domain_name(char *buf, const char *domain_name)
+{
+	size_t i;
+	char *p;
+
+	buf[0] = strcspn(domain_name, ".");
+	p = buf + 1;
+	for (i = 0; domain_name[i]; i++) {
+		if (domain_name[i] == '.')
+			p[i] = strcspn(domain_name + i + 1, ".");
+		else
+			p[i] = domain_name[i];
+	}
+	p[i] = 0L;
 }