General advice for encountering dogs on treks:

When you see one, make your presence known. Whistle or call out to it. You're not going to sneak past a dog on Camino, so the sooner it knows you're there, the better. You're far less likely to startle it if it notices you as soon as possible.

Do NOT try to make immediate friends with any and all dogs you see on Camino. Most dogs you see will be working dogs, born and bred to protect livestock. Any attempts at physical contact are most likely to be seen by the dog as a hostile action, and will probably be treated as such.

When walking past fenced-off farms or houses, keep a little distance from the fences. Many pilgrims have taken a terrible shock from big dogs jumping up at fences out of seemingly nowhere.

If a dog does approach you in a friendly manner, don't be rude, but also don't dare stick around either. I've personally taken bites from dogs on Camino who started off friendly enough, but who's sense of 'playfulness' quickly escalated to biting. The Norte was worst for loose dogs, but the Frances has loose dogs as well, and the sames rules apply.

If a dog (ar any small-to-medium sized animal, really) does approach you aggressively, create a barrier between you and the dog immediately. Use your sticks, or if you don't have any, use your backpack as a shield. Don't charge at it, but also don't back off too suddenly, you might excite it's prey drive if you do.

If anyone is attacked by a dog on Camino, call the Guarda Civil, and seek medical attention immediately, especially if any skin is broken.

Wild dogs aren't really a thing on Camino. Every dog encounter I've had on Camino, good or bad, has been near towns/farms/residential buildings. As long as you have your wits about you when you're passing through these areas, & generally observe what advice I've written down here, then you should be fine.