Project brussels from the OpenSolaris project revamped how link properties are managed, and their push to get rid of ndd and device-specific properties is now well underway! Link properties are actually pretty cool, and they can be displayed with the dladm utilities “show-linkprop” option:
$ dladm show-linkprop e1000g0
LINK PROPERTY PERM VALUE DEFAULT POSSIBLE
e1000g0 speed r- 0 0 --
e1000g0 autopush -- -- -- --
e1000g0 zone rw -- -- --
e1000g0 duplex r- half half half,full
e1000g0 state r- down up up,down
e1000g0 adv_autoneg_cap rw 1 1 1,0
e1000g0 mtu rw 1500 1500 --
e1000g0 flowctrl rw bi bi no,tx,rx,bi
e1000g0 adv_1000fdx_cap r- 1 1 1,0
e1000g0 en_1000fdx_cap rw 1 1 1,0
e1000g0 adv_1000hdx_cap r- 0 1 1,0
e1000g0 en_1000hdx_cap r- 0 1 1,0
e1000g0 adv_100fdx_cap r- 1 1 1,0
e1000g0 en_100fdx_cap rw 1 1 1,0
e1000g0 adv_100hdx_cap r- 1 1 1,0
e1000g0 en_100hdx_cap rw 1 1 1,0
e1000g0 adv_10fdx_cap r- 1 1 1,0
e1000g0 en_10fdx_cap rw 1 1 1,0
e1000g0 adv_10hdx_cap r- 1 1 1,0
e1000g0 en_10hdx_cap rw 1 1 1,0
e1000g0 maxbw rw -- -- --
e1000g0 cpus rw -- -- --
e1000g0 priority rw high high low,medium,high
As you can see in the above output, the typical speed, duplex, mtu and flowctrl properties are listed. In addition to those, the “maxbw” and “cpus” properties that were introduced with the recent crossbow putback are visible. The “maxbw” property is especially useful, since it allows you to limit how much bandwidth is available to an interface. Here is an example that caps bandwidth for an interface at 2Mb/s:
$ dladm set-linkprop -p maxbw=2m e1000g0
To see how this operates, you can use your favorite data transfer client:
$ scp techtalk1 192.168.1.10:
Password:
techtalk1.mp3 5% 2128KB 147.0KB/s 04:08 ETA
The read/write link properties can be changed on the fly with dladm, so increasing the “maxbw” property will allow the interface to consume additional bandwidth:
$ dladm set-linkprop -p maxbw=10m e1000g0
Once the bandwidth is increased, you can immediately see this reflected in the data transfer progress:
techtalk1.mp3 45% 17MB 555.3KB/s 00:38 ETA
Clearview rocks, and it’s awesome to see that link properties are going to be managed in a standard uniform way going forward! Nice! I incorrectly stated that the clearview project was responsible for this awesome work, when in fact network interface property unification is part of the brussels project. The original post was updated to reflect this.