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Fix a problem that shows up with a max packet count passed to pcap_dispatch().

If the last record read in by a read() from a BPF device isn't a
multiple of the alignment value for BPF_WORDALIGN(), we could increment
bp past ep; handle that case.

While we're at it, properly set p->bp and p->cc in the case where we
break out of the loop due to a pcap_breakloop() call.
master
Guy Harris 12 years ago
parent 7f1c9ba7ad
commit b26d8d2aa8
  1. 27
      pcap-bpf.c

@ -955,14 +955,28 @@ pcap_read_bpf(pcap_t *p, int cnt, pcap_handler callback, u_char *user)
* processed so far.
*/
if (p->break_loop) {
p->bp = bp;
p->cc = ep - bp;
/*
* ep is set based on the return value of read(),
* but read() from a BPF device doesn't necessarily
* return a value that's a multiple of the alignment
* value for BPF_WORDALIGN(). However, whenever we
* increment bp, we round up the increment value by
* a value rounded up by BPF_WORDALIGN(), so we
* could increment bp past ep after processing the
* last packet in the buffer.
*
* We treat ep < bp as an indication that this
* happened, and just set p->cc to 0.
*/
if (p->cc < 0)
p->cc = 0;
if (n == 0) {
p->break_loop = 0;
return (PCAP_ERROR_BREAK);
} else {
p->bp = bp;
p->cc = ep - bp;
} else
return (n);
}
}
caplen = bhp->bh_caplen;
@ -1014,6 +1028,11 @@ pcap_read_bpf(pcap_t *p, int cnt, pcap_handler callback, u_char *user)
if (++n >= cnt && cnt > 0) {
p->bp = bp;
p->cc = ep - bp;
/*
* See comment above about p->cc < 0.
*/
if (p->cc < 0)
p->cc = 0;
return (n);
}
} else {