diff options
| author | Mike Frantzen <frantzen@cvs.openbsd.org> | 2003-08-27 16:13:22 +0000 |
|---|---|---|
| committer | Mike Frantzen <frantzen@cvs.openbsd.org> | 2003-08-27 16:13:22 +0000 |
| commit | 94541b8379325b625efd9ea532daed507127a6fd (patch) | |
| tree | 13e95549250f527fbc291588094930fcc6bfe9f1 | |
| parent | 3bed8e9c367a29708af9fd6c3a66c5333fc5febb (diff) | |
it is supprisingly common (>4%) for some NAT and DSL routers to tweak MSS
by setting it to whatever is suitable for the link type. so we try a guessed
1460 MTU and 1500 MSS if the primary check fails.
algorithm tweak from Michal Zalewski
name a few constants too while I'm in there
| -rw-r--r-- | sys/net/pf_osfp.c | 32 |
1 files changed, 24 insertions, 8 deletions
diff --git a/sys/net/pf_osfp.c b/sys/net/pf_osfp.c index c72914aaba1..b7c72daa63c 100644 --- a/sys/net/pf_osfp.c +++ b/sys/net/pf_osfp.c @@ -1,4 +1,4 @@ -/* $OpenBSD: pf_osfp.c,v 1.1 2003/08/21 19:12:08 frantzen Exp $ */ +/* $OpenBSD: pf_osfp.c,v 1.2 2003/08/27 16:13:21 frantzen Exp $ */ /* * Copyright (c) 2003 Mike Frantzen <frantzen@w4g.org> @@ -372,16 +372,32 @@ pf_osfp_find(struct pf_osfp_list *list, struct pf_os_fingerprint *find, MATCH_INT(PF_OSFP_WSCALE_MOD, PF_OSFP_WSCALE_DC, fp_wscale) if ((f->fp_flags & PF_OSFP_WSIZE_DC) == 0) { if (f->fp_flags & PF_OSFP_WSIZE_MSS) { - if (find->fp_mss == 0 || - find->fp_wsize % find->fp_mss || + if (find->fp_mss == 0) + continue; + +/* Some "smart" NAT devices and DSL routers will tweak the MSS size and + * will set it to whatever is suitable for the link type. + */ +#define SMART_MSS 1460 + if ((find->fp_wsize % find->fp_mss || find->fp_wsize / find->fp_mss != - f->fp_wsize) + f->fp_wsize) && + (find->fp_wsize % SMART_MSS || + find->fp_wsize / SMART_MSS != + f->fp_wsize)) continue; } else if (f->fp_flags & PF_OSFP_WSIZE_MTU) { - if (find->fp_mss == 0 || - find->fp_wsize % (find->fp_mss + 40) || - find->fp_wsize / (find->fp_mss + 40) != - f->fp_wsize) + if (find->fp_mss == 0) + continue; + +#define MTUOFF (sizeof(struct ip) + sizeof(struct tcphdr)) +#define SMART_MTU (SMART_MSS + MTUOFF) + if ((find->fp_wsize % (find->fp_mss + MTUOFF) || + find->fp_wsize / (find->fp_mss + MTUOFF) != + f->fp_wsize) && + (find->fp_wsize % SMART_MTU || + find->fp_wsize / SMART_MTU != + f->fp_wsize)) continue; } else if (f->fp_flags & PF_OSFP_WSIZE_MOD) { if (f->fp_wsize == 0 || find->fp_wsize % |