[PATCH 1/4] dhcp: Set lease->bound_time before emitting event

[PATCH 1/4] dhcp: Set lease->bound_time before emitting event

[Andrew Zaborowski]

The event handler for L_DHCP_CLIENT_EVENT_LEASE_OBTAINED/RENEWED will
want to use the new lease->bound_time value for expiry time calculation
to we need to set it before we emit the events in the DHCP ACK handler.
---
 ell/dhcp.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/ell/dhcp.c b/ell/dhcp.c
index f9c0826..afd5c34 100644
--- a/ell/dhcp.c
+++ b/ell/dhcp.c
@@ -898,6 +898,7 @@ static void dhcp_client_rx_message(const void *data, size_t len, void *userdata,
 		CLIENT_ENTER_STATE(DHCP_STATE_BOUND);
 		l_timeout_remove(client->timeout_resend);
 		client->timeout_resend = NULL;
+		client->lease->bound_time = timestamp;
 
 		if (client->transport->bind) {
 			e = client->transport->bind(client->transport,
@@ -910,8 +911,6 @@ static void dhcp_client_rx_message(const void *data, size_t len, void *userdata,
 
 		dhcp_client_event_notify(client, r);
 
-		client->lease->bound_time = timestamp;
-
 		/*
 		 * Start T1, once it expires we will start the T2 timer.  If
 		 * we renew the lease, we will end up back here.
-- 
2.34.1

[PATCH 2/4] useful: Add a cleanup handler for fd variables

[Andrew Zaborowski]

Allow declaring an fd variable with a simple
    _auto_(close) int fd = -1;
to be able to skip the close() call.  This is useful for very simple
file accesses where it's not worth using l_io with
l_io_set_close_on_destroy.

As an example, update netconfig_proc_write_ipv6_setting to use
_auto_(close) where it helps in returning the errno from the read() call
(on error) which would otherwise be clobbered by the close() call.
---
 ell/netconfig.c |  5 ++---
 ell/useful.h    | 14 ++++++++++++++
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/ell/netconfig.c b/ell/netconfig.c
index d4487bd..19aaf56 100644
--- a/ell/netconfig.c
+++ b/ell/netconfig.c
@@ -968,7 +968,7 @@ static int netconfig_proc_write_ipv6_setting(struct l_netconfig *nc,
 {
 	char ifname[IF_NAMESIZE];
 	_auto_(l_free) char *filename = NULL;
-	int fd;
+	_auto_(close) int fd = -1;
 	int r;
 
 	if (unlikely(!if_indextoname(nc->ifindex, ifname)))
@@ -982,8 +982,7 @@ static int netconfig_proc_write_ipv6_setting(struct l_netconfig *nc,
 		return -errno;
 
 	r = L_TFR(write(fd, value, strlen(value)));
-	L_TFR(close(fd));
-	return r;
+	return r > 0 ? 0 : -errno;
 }
 
 LIB_EXPORT struct l_netconfig *l_netconfig_new(uint32_t ifindex)
diff --git a/ell/useful.h b/ell/useful.h
index 4c8b23e..791fa20 100644
--- a/ell/useful.h
+++ b/ell/useful.h
@@ -20,6 +20,11 @@
  *
  */
 
+#include <unistd.h>
+#include <errno.h>
+
+#include <ell/util.h>
+
 #define align_len(len, boundary) (((len)+(boundary)-1) & ~((boundary)-1))
 
 #define likely(x)   __builtin_expect(!!(x), 1)
@@ -65,6 +70,15 @@ static inline unsigned char bit_field(const unsigned char oct,
 #define _auto_(func)					\
 	__AUTODESTRUCT(func)
 
+/* Enables declaring _auto_(close) int fd = <-1 or L_TFR(open(...))>; */
+inline __attribute__((always_inline)) void close_cleanup(void *p)
+{
+	int fd = *(int *) p;
+
+	if (fd >= 0)
+		L_TFR(close(fd));
+}
+
 /*
  * Trick the compiler into thinking that var might be changed somehow by
  * the asm
-- 
2.34.1

[PATCH 3/4] netconfig: Restore net.ipv6.conf...disable_ipv6 on stop

[Andrew Zaborowski]

Since we write the net.ipv6.conf.<ifname>.disable_ipv6 option to 0 when
enabling DHCPv6, reset it to its original value when stopping netconfig.
---
 ell/netconfig.c | 69 ++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 59 insertions(+), 10 deletions(-)

diff --git a/ell/netconfig.c b/ell/netconfig.c
index 19aaf56..f48018b 100644
--- a/ell/netconfig.c
+++ b/ell/netconfig.c
@@ -35,6 +35,8 @@
 #include <sys/stat.h>
 #include <fcntl.h>
 #include <unistd.h>
+#include <stdlib.h>
+#include <stdio.h>
 
 #include "private.h"
 #include "useful.h"
@@ -83,6 +85,7 @@ struct l_netconfig {
 	unsigned int ifaddr6_dump_cmd_id;
 	struct l_queue *icmp_route_data;
 	struct l_acd *acd;
+	unsigned int orig_disable_ipv6;
 
 	/* These objects, if not NULL, are owned by @addresses and @routes */
 	struct l_rtnl_address *v4_address;
@@ -962,14 +965,15 @@ static void netconfig_icmp6_event_handler(struct l_icmp6_client *client,
 		netconfig_emit_event(nc, AF_INET6, L_NETCONFIG_EVENT_UPDATE);
 }
 
-static int netconfig_proc_write_ipv6_setting(struct l_netconfig *nc,
-						const char *setting,
-						const char *value)
+static int netconfig_proc_write_ipv6_uint_setting(struct l_netconfig *nc,
+							const char *setting,
+							unsigned int value)
 {
 	char ifname[IF_NAMESIZE];
 	_auto_(l_free) char *filename = NULL;
 	_auto_(close) int fd = -1;
 	int r;
+	char valuestr[20];
 
 	if (unlikely(!if_indextoname(nc->ifindex, ifname)))
 		return -errno;
@@ -981,10 +985,46 @@ static int netconfig_proc_write_ipv6_setting(struct l_netconfig *nc,
 	if (unlikely(fd < 0))
 		return -errno;
 
-	r = L_TFR(write(fd, value, strlen(value)));
+	snprintf(valuestr, sizeof(valuestr), "%u", value);
+	r = L_TFR(write(fd, valuestr, strlen(valuestr)));
 	return r > 0 ? 0 : -errno;
 }
 
+static long netconfig_proc_read_ipv6_uint_setting(struct l_netconfig *nc,
+							const char *setting)
+{
+	char ifname[IF_NAMESIZE];
+	_auto_(l_free) char *filename = NULL;
+	_auto_(close) int fd = -1;
+	int r;
+	char valuestr[20];
+	long value;
+	char *endp;
+
+	if (unlikely(!if_indextoname(nc->ifindex, ifname)))
+		return -errno;
+
+	filename = l_strdup_printf("/proc/sys/net/ipv6/conf/%s/%s",
+					ifname, setting);
+
+	fd = L_TFR(open(filename, O_RDONLY));
+	if (unlikely(fd < 0))
+		return -errno;
+
+	r = L_TFR(read(fd, valuestr, sizeof(valuestr) - 1));
+	if (unlikely(r < 1))
+		return r == 0 ? -EINVAL : -errno;
+
+	valuestr[r - 1] = '\0';
+	errno = 0;
+	value = strtoul(valuestr, &endp, 10);
+
+	if (unlikely(errno || !L_IN_SET(*endp, '\n', '\0')))
+		return -EINVAL;
+
+	return value;
+}
+
 LIB_EXPORT struct l_netconfig *l_netconfig_new(uint32_t ifindex)
 {
 	struct l_netconfig *nc;
@@ -1019,7 +1059,7 @@ LIB_EXPORT struct l_netconfig *l_netconfig_new(uint32_t ifindex)
 					nc, NULL);
 
 	/* Disable in-kernel autoconfiguration for the interface */
-	netconfig_proc_write_ipv6_setting(nc, "accept_ra", "0");
+	netconfig_proc_write_ipv6_uint_setting(nc, "accept_ra", 0);
 
 	return nc;
 }
@@ -1554,13 +1594,15 @@ static void netconfig_ifaddr_ipv6_dump_done_cb(void *user_data)
 	nc->ifaddr6_dump_cmd_id = 0;
 
 	/* "do not generate a link-local address" */
-	netconfig_proc_write_ipv6_setting(nc, "addr_gen_mode", "1");
+	netconfig_proc_write_ipv6_uint_setting(nc, "addr_gen_mode", 1);
 	/* "generate address based on EUI64 (default)" */
-	netconfig_proc_write_ipv6_setting(nc, "addr_gen_mode", "0");
-	/* "enable IPv6 operation" */
-	netconfig_proc_write_ipv6_setting(nc, "disable_ipv6", "0");
+	netconfig_proc_write_ipv6_uint_setting(nc, "addr_gen_mode", 0);
 
-	/* TODO: save original values and reset in l_netconfig_stop() */
+	/* "enable IPv6 operation" */
+	nc->orig_disable_ipv6 =
+		netconfig_proc_read_ipv6_uint_setting(nc, "disable_ipv6");
+	if (nc->orig_disable_ipv6)
+		netconfig_proc_write_ipv6_uint_setting(nc, "disable_ipv6", 0);
 }
 
 LIB_EXPORT bool l_netconfig_start(struct l_netconfig *netconfig)
@@ -1680,6 +1722,13 @@ LIB_EXPORT void l_netconfig_stop(struct l_netconfig *netconfig)
 	l_dhcp6_client_stop(netconfig->dhcp6_client);
 
 	l_acd_destroy(l_steal_ptr(netconfig->acd));
+
+	if (netconfig->orig_disable_ipv6) {
+		netconfig_proc_write_ipv6_uint_setting(netconfig,
+						"disable_ipv6",
+						netconfig->orig_disable_ipv6);
+		netconfig->orig_disable_ipv6 = 0;
+	}
 }
 
 LIB_EXPORT struct l_dhcp_client *l_netconfig_get_dhcp_client(
-- 
2.34.1

[PATCH 4/4] netconfig: Fix leaking domain name string

[Andrew Zaborowski]

In l_netconfig_get_domain_names we had two
l_dhcp_lease_get_domain_name() calls and only saved one of the values.
l_dhcp_lease_get_domain_name() internally does an strdup so we own the
returned string.

Reported by Coverity Scan as CID 379209.
---
 ell/netconfig.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/ell/netconfig.c b/ell/netconfig.c
index f48018b..28afa9b 100644
--- a/ell/netconfig.c
+++ b/ell/netconfig.c
@@ -1908,15 +1908,16 @@ LIB_EXPORT char **l_netconfig_get_domain_names(struct l_netconfig *netconfig)
 	char **ret = NULL;
 	const struct l_dhcp_lease *v4_lease;
 	const struct l_dhcp6_lease *v6_lease;
+	char *dn;
 
 	if (netconfig->v4_domain_names_override)
 		netconfig_strv_cat(&ret, netconfig->v4_domain_names_override,
 					false);
 	else if ((v4_lease =
 			l_dhcp_client_get_lease(netconfig->dhcp_client)) &&
-			l_dhcp_lease_get_domain_name(v4_lease)) {
+			(dn = l_dhcp_lease_get_domain_name(v4_lease))) {
 		ret = l_new(char *, 2);
-		ret[0] = l_dhcp_lease_get_domain_name(v4_lease);
+		ret[0] = dn;
 	}
 
 	if (netconfig->v6_dns_override)
-- 
2.34.1

Re: [PATCH 1/4] dhcp: Set lease->bound_time before emitting event

[Denis Kenzior]

Hi Andrew,

On 7/1/22 08:32, Andrew Zaborowski wrote:
> The event handler for L_DHCP_CLIENT_EVENT_LEASE_OBTAINED/RENEWED will
> want to use the new lease->bound_time value for expiry time calculation
> to we need to set it before we emit the events in the DHCP ACK handler.
> ---
>   ell/dhcp.c | 3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)
> 

All applied, thanks.

Regards,
-Denis