Don't know the exact size of your bulldog but if it's about 18 - 20 inches at the shoulder you would need at least a 2 ft. high enclosure.
Ex Pens have a gate Amazon.com : Midwest Gold- Zinc Indoor/Outdoor Exercise Pet Pen, 24"W x 42"H : Pet Playpens : Pet Supplies
Depending on how your dog will react to a passing dog you might be able to combine pen for the gate with the plastic fence Carol suggested. If on the other hand your dog tends to be rambunctious about wanting to go see other dogs or passing people you might want to go with multiple ex pens and just latch them together. They are designed so they can be combined by latching them onto each other.
One is 16 ft. of fence, whole 10 x 10 canopy is 40 ft. so you should be able to use 3 pens and extend it past canopy or just fold a panel or two so they double up to make it shorter. I should warn you that is a lot of metal, you should hit the pet store and check the size and weight
of one before getting 3. One is probably big enough for two dogs, two is more than enough space. But if you wanted to make your canopy into a yard you would not be the first person to do so.
I use a cable with a chain on it. The cable is about 7 ft. and the chain 6 ft. The ends of the cable have a loop. I stretch the cable in a straight line and stake it down to the ground through each end loop with 16 inch barn spikes with a washer on them.
Because the dog has nothing to walk around that sticks up they don't get chain wound up. Because the area the dog is in is more of a rectangle than a circle it's easier to align with stuff so they don't get tangled with poles, chairs and such.
When they pull against the cable the chain slides rather than allowing the force to pull on the stakes. Pulling in line with the cable both stakes are taking the load. My husky broke his collar without pulling the cable loose.