The defaultGateway is empty after set IPv4 Static Address

[chnguyen-ampere]

Is this the right place to submit this?

• This is not a security vulnerability or a crashing bug
• This is not a question about how to use OpenBMC
• This is not a bug in an OpenBMC fork or a bug in code still under code review.
• This is not a request for a new feature.

Bug Description

I'm testing on bmcweb revision : 4d7b5dd (Commits on Mar 14, 2025).

I tried to use Redfish command to set a static IPv4 address and defaultGateway. After that, I saw the defaultGateway is empty.

Step to reproduce:
Step 1: Check the defaultGateway is valid and DHCP v4 mode is Enable

root@board:~# busctl introspect xyz.openbmc_project.Network /xyz/openbmc_project/network/eth0
NAME                                              TYPE      SIGNATURE RESULT/VALUE                             FLAGS
org.freedesktop.DBus.Introspectable               interface -         -                                        -
.Introspect                                       method    -         s                                        -
org.freedesktop.DBus.Peer                         interface -         -                                        -
.GetMachineId                                     method    -         s                                        -
.Ping                                             method    -         -                                        -
org.freedesktop.DBus.Properties                   interface -         -                                        -
.Get                                              method    ss        v                                        -
.GetAll                                           method    s         a{sv}                                    -
.Set                                              method    ssv       -                                        -
.PropertiesChanged                                signal    sa{sv}as  -                                        -
xyz.openbmc_project.Collection.DeleteAll          interface -         -                                        -
.DeleteAll                                        method    -         -                                        -
xyz.openbmc_project.Network.EthernetInterface     interface -         -                                        -
.AutoNeg                                          property  b         true                                     emits-change
.DHCP4                                            property  b         true                                     emits-change writable
.DHCP6                                            property  b         true                                     emits-change writable
.DHCPEnabled                                      property  s         "xyz.openbmc_project.Network.Ethernet... emits-change writable
.DefaultGateway                                   property  s         "10.39.122.1"                            emits-change writable
.DefaultGateway6                                  property  s         ""                                       emits-change writable
.DomainName                                       property  as        0                                        emits-change writable
.EmitLLDP                                         property  b         false                                    emits-change writable
.IPv6AcceptRA                                     property  b         true                                     emits-change writable
.InterfaceName                                    property  s         "eth0"                                   const
.LinkLocalAutoConf                                property  s         "xyz.openbmc_project.Network.Ethernet... emits-change writable
.LinkUp                                           property  b         true                                     emits-change
.MTU                                              property  u         1500                                     emits-change writable
.NICEnabled                                       property  b         true                                     emits-change writable
.NTPServers                                       property  as        0                                        emits-change writable
.Nameservers                                      property  as        3 "10.38.20.10" "10.38.18.70" "10.38.... emits-change
.Speed                                            property  u         1000                                     emits-change
.StaticNTPServers                                 property  as        0                                        emits-change writable
.StaticNameServers                                property  as        0                                        emits-change writable
xyz.openbmc_project.Network.IP.Create             interface -         -                                        -
.IP                                               method    ssys      o                                        -
xyz.openbmc_project.Network.MACAddress            interface -         -                                        -
.MACAddress                                       property  s         "9c:c2:66:77:88:99"                      emits-change writable
xyz.openbmc_project.Network.Neighbor.CreateStatic interface -         -                                        -
.Neighbor                                         method    ss        o                                        -
xyz.openbmc_project.Network.StaticGateway.Create  interface -         -                                        -
.StaticGateway

Step 2: Add a staic IPv4 address by redfish command with IPv4 address and defaultGateway is valid.

curl -X PATCH --user root:0penBmc -H "Content-Type: application/json" -H "If-match: *" --insecure https://${BMC_IP}/redfish/v1/Managers/bmc/EthernetInterfaces/eth0 -d '{"IPv4StaticAddresses": [{"Address": "10.39.122.50", "Gateway": "10.39.122.1", "SubnetMask": "255.255.255.0"}]}'

Step 3: Check the defaultGateway
=> The defaultGateway is empty

root@board:~# busctl introspect xyz.openbmc_project.Network /xyz/openbmc_project/network/eth0
NAME                                              TYPE      SIGNATURE RESULT/VALUE                             FLAGS
org.freedesktop.DBus.Introspectable               interface -         -                                        -
.Introspect                                       method    -         s                                        -
org.freedesktop.DBus.Peer                         interface -         -                                        -
.GetMachineId                                     method    -         s                                        -
.Ping                                             method    -         -                                        -
org.freedesktop.DBus.Properties                   interface -         -                                        -
.Get                                              method    ss        v                                        -
.GetAll                                           method    s         a{sv}                                    -
.Set                                              method    ssv       -                                        -
.PropertiesChanged                                signal    sa{sv}as  -                                        -
xyz.openbmc_project.Collection.DeleteAll          interface -         -                                        -
.DeleteAll                                        method    -         -                                        -
xyz.openbmc_project.Network.EthernetInterface     interface -         -                                        -
.AutoNeg                                          property  b         true                                     emits-change
.DHCP4                                            property  b         true                                     emits-change writable
.DHCP6                                            property  b         true                                     emits-change writable
.DHCPEnabled                                      property  s         "xyz.openbmc_project.Network.Ethernet... emits-change writable
.DefaultGateway                                   property  s         ""                                       emits-change writable
.DefaultGateway6                                  property  s         ""                                       emits-change writable
.DomainName                                       property  as        0                                        emits-change writable
.EmitLLDP                                         property  b         false                                    emits-change writable
.IPv6AcceptRA                                     property  b         true                                     emits-change writable
.InterfaceName                                    property  s         "eth0"                                   const
.LinkLocalAutoConf                                property  s         "xyz.openbmc_project.Network.Ethernet... emits-change writable
.LinkUp                                           property  b         true                                     emits-change
.MTU                                              property  u         1500                                     emits-change writable
.NICEnabled                                       property  b         true                                     emits-change writable
.NTPServers                                       property  as        0                                        emits-change writable
.Nameservers                                      property  as        3 "10.38.20.10" "10.38.18.70" "10.38.... emits-change
.Speed                                            property  u         1000                                     emits-change
.StaticNTPServers                                 property  as        0                                        emits-change writable
.StaticNameServers                                property  as        0                                        emits-change writable
xyz.openbmc_project.Network.IP.Create             interface -         -                                        -
.IP                                               method    ssys      o                                        -
xyz.openbmc_project.Network.MACAddress            interface -         -                                        -
.MACAddress                                       property  s         "9c:c2:66:77:88:99"                      emits-change writable
xyz.openbmc_project.Network.Neighbor.CreateStatic interface -         -                                        -
.Neighbor                                         method    ss        o                                        -
xyz.openbmc_project.Network.StaticGateway.Create  interface -         -                                        -
.StaticGateway                                    method    ss        o                                        -

Version

I'm testing on bmcweb revision : 4d7b5dd (Commits on Mar 14, 2025).

Additional Information

Other observations, I checked the source code of the bmcweb. It seems when we patch a redfish command to update IPv4StaticAddresses then the handleDHCPPatch also is called before https://github.com/openbmc/bmcweb/blob/master/redfish-core/lib/ethernet.hpp#L2416

That makes the defaultGateway is removed in the handleDHCPPatch.
But in handleIPv4StaticPatch function, the defaultGateway can not be added again because the ethData.defaultGateway can be not updated after the handleDHCPPatch removed the defaultGateway.

[chandramohan83]

I am seeing this issue for multiple use cases

1. When Invalid static IP is provided in PATCH request Gateway is getting cleared
   2)When hostname is patched Gateway is getting cleared
2. when PATCH name servers Gateway is getting cleared
   3)when NIC has both static and DHCP ip address but NIC is in DHCP mode. If I delete the static IP the gateway is getting cleared

etc .. .....

[M-Kamalesh]

I am also facing this issue when using PATCH command on FQDN property.
Hi @wak-google , do you think that phosphor-networkd is doing any deletion of gateway while updating the ethernet interface properties?
Please share your suggestions.

[garybeihl]

It looks like there are two related issues in ethernet.hpp:

1. Redundant gateway clear in handleIPv4StaticPatch()

When setting a static IPv4 address with a gateway, the handler issues two D-Bus calls to DefaultGateway:

• Line 1703: Clear gateway to ""
• Line 1754: Set gateway to the new value

The intermediate clear is unnecessary — the set call alone is sufficient. Consolidating into a single call removes an extra D-Bus round-trip and an unnecessary transient empty state.

2. handleDHCPPatch() clears gateway unconditionally

handleDHCPPatch() is called on every PATCH request — unlike every other sub-handler which is guarded by whether its properties are present in the request body. Line 1410 clears DefaultGateway whenever DHCPv4 is currently enabled. This means PATCHing unrelated properties like hostname, nameservers, or FQDN clears the gateway as a side effect. This is the root cause of the issues reported here.

Fix for issue 1: Consolidate the two gateway calls in handleIPv4StaticPatch() into a single call at the end — either set the new value or clear it when all static IPs are removed.

Fix for issue 2: Condition the clear in handleDHCPPatch() so it only fires when DHCPv4 is being newly enabled (static → DHCP transition). When static addresses are being changed, handleIPv4StaticPatch() already handles the gateway independently, so the clear in handleDHCPPatch() is redundant in that case.

Gerrit change: 88103

[edtanous]

with no ordering guarantee

How did you make this assessment? It doesn't seem correct to me, there is some ordering guaranteed by the single dbus connection.

Proposed fix for issue 1

Please post patches to gerrit where we can review them as code. Snippets are difficult to review for correctness.

so it only fires when DHCPv4 is being newly enabled

This would break cases where the static addresses are changed without changing the DHCP setting.

[garybeihl]

Thanks for the feedback, Ed.

You're right — this isn't a race between two calls on the same connection. My Gerrit change (88103) still removes an unnecessary intermediate clear and an extra D-Bus round-trip, but I'll update the commit message (and my earlier comment here) to not claim a race.

It still seems to me that the real root cause for the reports in this issue (hostname, FQDN, nameserver PATCHes clearing the gateway) is that handleDHCPPatch() is called unconditionally on every PATCH request — unlike every other sub-handler which is guarded by whether its properties are present in the request body. So when DHCPv4 is active and a user PATCHes only HostName, handleDHCPPatch() still runs and clears the gateway.

Re: the guard condition: I'm not sure that !ipv4Active && nextv4DHCPState is too narrow. The gateway clearing in handleDHCPPatch() is redundant when static addresses are being changed, because handleIPv4StaticPatch() always handles the gateway itself. The only case where handleDHCPPatch() clearing matters is when DHCP is being newly enabled — and our condition covers that.

[edtanous]

unnecessary intermediate clear

To my understanding it's not unnecessary. phosphor-network will fail to delete a static ip address if the gateway is still active. Basically the patch flow is, clear the gateway, set the new IPs, while determining the new gateway, set the gateway. A lot of this is the way phosphor-network modeled things causes some complexity. I suspect these days there's a much simpler way to approach this. As is, we're taking more read/modify/write trips than we would prefer.

[garybeihl]

... phosphor-network will fail to delete a static ip address if the gateway is still active.

Can you give a little more detail here? I'm having trouble finding this in the source code. The delete_() method in ipaddress.cpp doesn't appear to check for an active gateway. Also, I ran an end-to-end QEMU test with my proposed changes. On evb-ast2600, I set a static IP with gateway 10.0.2.1, then deleted the static IP via Redfish PATCH (setting it to null). phosphor-networkd deleted the IP successfully and the gateway was cleared without errors.