Why does DFS in Dinic’s Algorithm finds a blocking flow

I came upon this implementation of the dfs in Dinic’s algorithm written in Python

def dfs(c, f, current, capacity):   tmp = capacity # What's the purpose of that?    # we want to get to the sink, but we want it to be a blocking flow path   if current == NROW - 1:     return capacity    for i in range(NROW):     is_next = levels[i] == levels[current] + 1     residual_capacity = c[current][i] - f[current][i]     has_more_capacity = residual_capacity > 0     if is_next and has_more_capacity:       min_capacity_so_far = min(tmp, residual_capacity)       flow = dfs(c, f, i, min_capacity_so_far)       f[current][i] += flow       f[i][current] -= flow       tmp -= flow # Why do we do that   return capacity - tmp # Why do we return capacity - tmp 

How do we know that this dfs finds a blocking path? Also, I can’t seem to understand the usage of the temp variable.

Thanks in advance!