tcp: use enum for all congestion control signals

[rscheff]

Summary

Facilitate easier troubleshooting by enumerating
all congestion control signals. Typecast the
enum to int, when a cc module uses private signals.
While there, ensure that the currently used
private signals are unique too. While not strictly
necessary to use individual bits, retain the
possibility of combined signals for the future.

No external change.

[glebius]

sys/netinet/cc/cc_cdg.c

457

Did compiler ask you to add the cast? enums are ints by standard, so if compiler did, that means something is off here. If it did not, there is no reason for this cast.

[rscheff]

sys/netinet/cc/cc_cdg.c

457

Yes. The "private" signals are not part of the enum, and if a cc module wants to refer to them in a switch{}, the cast is necessary to silence that warning; cc_cdg, cc_chd and cc_vegas make use of these private signals. The alternative would be to add CC_CDG_DELAY, CC_CHD_DELAY, and CC_VEGAS_DELAY into cc.h as global enums.

I thought to leave these only in the scope of the respective cc module, and do the cast to int instead.

[glebius]

sys/netinet/cc/cc_cdg.c

457

I see. Unfortunately enums are not expandable. One hack that can be done is this:

#define CC_GENERIC_ENUM  CC_ACK = 1, CC_DUPACK = .......................

enum cdgsignal_t {CC_GENERIC_ENUM, CC_CDG_DELAY = ...};

Probably using int cast is simpler.

[rscheff]

sys/netinet/cc/cc_cdg.c

457

Presumably, if you create a new type, for gdb to consistenly decode these private signals, you would have to use that type in the function definition - which would collide with the cc module function block definition; so to compile, you'd typecast within the switch, and loose gdb visibility again. So probably not much gain after all...

[rscheff]

• rebase main