Combine SACK RecoveryPoint (sack_newdata) with Reno Recover (snd_recover) and remove sack_newdata.
sack_newdata was added during the original commit when SACK support was included in the BSD stack.
Both variables (snd_recover and sack_newdata) track the sequence number of snd_nxt when entering fast recovery, and are called similar in the respective RFCs. For some reason a new variable was added rather than using the existing one. While looking into improving the SACK scoreboard in preparation to implement RFC6675 and RFC6937 i found that more modern SACK code also uses sack_newdata inconsistently (e.g. only for pipe calculation).
A recent change disentangled the kernel TCPCB from access/reference by userspace programs, thus removing this variable (ABI) should be safe to do now.