It was in this way that the grey cub learned other attributes of his mother than the soft, soothing, tongue. In his insistent crawling toward the light, he discovered in her a nose that with a sharp nudge administered rebuke, and later, a paw, that crushed him down and rolled him over and over with swift, calculating stroke. (6.6)
Confinement in the wild seems like a safety thing here. Mom keeps White Fang away from the cave entrance so that he doesn't get eaten by… well, by any ol' thing that could happen along. That makes confinement a real trap—you get safety in exchange for the ability to go wherever you want—and London plays with it in other points of the book as well.
Then, at the same instant, he saw and smelt. Before him, sitting silently on their haunches, were five live things, the like of which he had never seen before. It was his first glimpse of mankind. (9.2)
Mankind: the ultimate confinement? Once White Fang joins them, he can't ever go back. The question becomes whether he's ever free at all once he goes to them.
He was homesick. He felt a vacancy in him, a need for the hush and quietude of the stream and the cave in the cliff. Life had become too populous. (9.39)
Homesickness is probably another word for freedom here. White Fang understands what he's lost and he's pretty bummed about it… no matter how much free fish he gets.
His bondage had softened him. Irresponsibility had weakened him. He had forgotten how to shift for himself. The night yawned about him. (12.5)
Here's confinement of a mental sort. White Fang's gotten soft and can't fend for himself. It's kind of hard do whatever you please in the wilderness when you're afraid of it and don't know what to do. Does that mean he can't ever be free again?
But it did not all happen in a day, this giving over of himself, body and soul, to the man-animals. He could not immediately forego his wild heritage and his memories of the Wild. (10.5)
Physical confinement takes place in a minute. But mental confinement, the kind that really sticks? That takes time. Unfortunately, once it gets set up, he can't ever really get rid of it. Bummer, wolf dude.
White Fang was glad to acknowledge his lordship, but it was a lordship based upon superior intelligence and brute strength. (13.16)
London sets the terms of the engagement. Grey Beaver has the tools to command and imprison White Fang. The question is, does that make it okay?
Beauty Smith took passage for himself and White Fang on a steamboat bound up the Yukon to Dawson. White Fang had now achieved a reputation in the land. As "the Fighting Wolf" he was known far and wide, and the cage in which he was kept on the steam-boat's deck was usually surrounded by curious men. (17.7)
We have confinement in the most serious terms here, the worst parts of civilization crammed right down White Fang's poor little throat.
It was necessary that he should have some god. The lordship of man was a need of his nature. (20.24)
White Fang needs to feel like a good boy, and therefore he makes himself the slave of a man. Sure, this one doesn't beat him and lets him feel loved and all that, but it's still a big step for a wild animal who hadn't experienced anything good in his confinement.
This expression of abandon and surrender, of absolute trust, he reserved for the master alone. (23.10)
Here, White Fang gives himself to the confinement freely. He chooses to be the master's good dog. It feels like confinement, doesn't it? But if it is, then why does it make White Fang feels so happy?
Bound down a prisoner, denied even movement by the plaster casts and bandages, White Fang lingered out the weeks. (25.30)
This may be a last bit of symbolism before the very end of the book: White Fang confined by plaster casts after taking three in the chest for his beloved master. London may be helping us to feel his freedom when the bandages come off, a last release after all those years in cages and chains. Or maybe it's the sense that he's still bound, that saving his master's life was a way of showing that he's still caught up in a trap he can't escape.