Can't find wifi on newly installed Ubuntu 14.04

I just installed ubuntu 14.04, but I found no wifi on it.

$ sudo modprobe -r iwlwfi
modprobe: FATAL: module iwlwfi not found

with

lspci -vq|grep -i wireless

I get nothing

while:

lspci -vq|grep -i realtek

I get

03:00.0 Unassigned class [ff00]: Realtek Semiconductor Co., Ltd. RTS5229 PCI Express Card Reader (rev 01)
05:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 07)

lspci -nn |grep -i net

I get:

04:00.0 Network controller [0280]: Broadcom Corporation BCM43142 802.11b/g/n [14e4:4365] (rev 01)
05:00.0 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller [10ec:8168] (rev 07)

How to deal with this?

My laptop is a Thinkpad E431

Solution 1:

Your Broadcom Corporation BCM43142 802.11b/g/n [14e4:4365] works with the Broadcom proprietary driver. Please connect with ethernet and open a terminal and do:

sudo apt-get update
sudo apt-get install bcmwl-kernel-source

After it finishes, detach the ethernet and your wireless should be working.