/* * Compute TCP retransmission timer, following RFC2988. * This macro returns a value in slow timeout ticks. * * Section 2.2 requires that the RTO value be * srtt + max(G, 4*RTTVAR) * where G is the clock granularity. * * This comment has not necessarily been updated for the new storage * representation: * * Because of the way we do the smoothing, srtt and rttvar * will each average +1/2 tick of bias. When we compute * the retransmit timer, we want 1/2 tick of rounding and * 1 extra tick because of +-1/2 tick uncertainty in the * firing of the timer. The bias will give us exactly the * 1.5 tick we need. But, because the bias is * statistical, we have to test that we don't drop below * the minimum feasible timer (which is 2 ticks). * This macro assumes that the value of 1<<TCP_RTTVAR_SHIFT * is the same as the multiplier for rttvar. * * This macro appears to be wrong; it should be checking rttvar*4 in * ticks and making sure we use 1 instead if rttvar*4 rounds to 0. It * appears to be treating srtt as being in the old storage * representation, resulting in a factor of 4 extra. */