[PATCH 1/2] netconfig: Set preferred lifetimes on DHCP addresses

[PATCH 1/2] netconfig: Set preferred lifetimes on DHCP addresses

[Andrew Zaborowski]

We receive one lease lifetime value for a DHCP lease so we were setting
the preferred lifetime for the RTNL address to 0 and the valid lifetime
to the lease lifetime.  If either value is non-zero rtnl.c will send
both to the kernel and the 0 preferred lifetime is treated as literal
zero and the address becomes deprecated immediately.  This doesn't
matter for most usages but systemd-resolved would check whether a link
has a non-deprecated address before setting the link's
"unicast_relevant" flag and internally wouldn't create a DNS "scope" on
the link or set its "DefaultRoute" flag both of which are required for
it to want to resolve names.
---
 ell/netconfig.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/ell/netconfig.c b/ell/netconfig.c
index 76b18a7..8ded113 100644
--- a/ell/netconfig.c
+++ b/ell/netconfig.c
@@ -405,8 +405,8 @@ static void netconfig_set_dhcp_lifetimes(struct l_netconfig *nc, bool updated)
 	uint64_t expiry = l_dhcp_lease_get_start_time(lease) +
 		lifetime * L_USEC_PER_SEC;
 
-	l_rtnl_address_set_lifetimes(nc->v4_address, 0, lifetime);
-	l_rtnl_address_set_expiry(nc->v4_address, 0, expiry);
+	l_rtnl_address_set_lifetimes(nc->v4_address, lifetime, lifetime);
+	l_rtnl_address_set_expiry(nc->v4_address, expiry, expiry);
 
 	if (updated && !netconfig_address_exists(nc->addresses.added,
 							nc->v4_address))
-- 
2.34.1

[PATCH 2/2] dhcp: Simplify check in BPF filter

[Andrew Zaborowski]

Instead of separately loading and testing the low 4 bits and the high 4
bits of the IP Version+Header length byte in the DHCP frame, test both
in one operation.  The filter can be further shortened but with some
loss of readability.
---
 ell/dhcp-transport.c | 14 ++------------
 1 file changed, 2 insertions(+), 12 deletions(-)

diff --git a/ell/dhcp-transport.c b/ell/dhcp-transport.c
index c4cf0ca..41b582d 100644
--- a/ell/dhcp-transport.c
+++ b/ell/dhcp-transport.c
@@ -389,18 +389,8 @@ static int kernel_raw_socket_open(uint32_t ifindex, uint16_t port, uint32_t xid)
 		BPF_STMT(BPF_RET + BPF_K, 0),
 		/* A <- IP version + Header length */
 		BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 0),
-		/* A <- A & 0xf0 (Mask off version */
-		BPF_STMT(BPF_ALU + BPF_AND + BPF_K, 0xf0),
-		/* A == IPVERSION (shifted left 4) ? */
-		BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPVERSION << 4, 1, 0),
-		/* ignore */
-		BPF_STMT(BPF_RET + BPF_K, 0),
-		/* A <- IP version + Header length */
-		BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 0),
-		/* A <- A & 0x0f (Mask off IP Header Length */
-		BPF_STMT(BPF_ALU + BPF_AND + BPF_K, 0x0f),
-		/* A == 5 ? */
-		BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 5, 1, 0),
+		/* IP version == IPVERSION && Header length == 5 ? */
+		BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, (IPVERSION << 4) | 5, 1, 0),
 		/* ignore */
 		BPF_STMT(BPF_RET + BPF_K, 0),
 		/* A <- IP protocol */
-- 
2.34.1

Re: [PATCH 1/2] netconfig: Set preferred lifetimes on DHCP addresses

[Denis Kenzior]

Hi Andrew,

On 10/7/22 13:02, Andrew Zaborowski wrote:
> We receive one lease lifetime value for a DHCP lease so we were setting
> the preferred lifetime for the RTNL address to 0 and the valid lifetime
> to the lease lifetime.  If either value is non-zero rtnl.c will send
> both to the kernel and the 0 preferred lifetime is treated as literal
> zero and the address becomes deprecated immediately.  This doesn't
> matter for most usages but systemd-resolved would check whether a link
> has a non-deprecated address before setting the link's
> "unicast_relevant" flag and internally wouldn't create a DNS "scope" on
> the link or set its "DefaultRoute" flag both of which are required for
> it to want to resolve names.
> ---
>   ell/netconfig.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 

Both applied, thanks.

Regards,
-Denis