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.
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7f1c9ba7ad
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27
pcap-bpf.c
27
pcap-bpf.c
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@ -955,14 +955,28 @@ pcap_read_bpf(pcap_t *p, int cnt, pcap_handler callback, u_char *user)
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* processed so far.
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*/
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if (p->break_loop) {
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p->bp = bp;
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p->cc = ep - bp;
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/*
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* ep is set based on the return value of read(),
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* but read() from a BPF device doesn't necessarily
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* return a value that's a multiple of the alignment
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* value for BPF_WORDALIGN(). However, whenever we
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* increment bp, we round up the increment value by
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* a value rounded up by BPF_WORDALIGN(), so we
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* could increment bp past ep after processing the
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* last packet in the buffer.
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*
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* We treat ep < bp as an indication that this
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* happened, and just set p->cc to 0.
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*/
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if (p->cc < 0)
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p->cc = 0;
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if (n == 0) {
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p->break_loop = 0;
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return (PCAP_ERROR_BREAK);
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} else {
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p->bp = bp;
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p->cc = ep - bp;
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} else
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return (n);
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}
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}
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caplen = bhp->bh_caplen;
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@ -1014,6 +1028,11 @@ pcap_read_bpf(pcap_t *p, int cnt, pcap_handler callback, u_char *user)
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if (++n >= cnt && cnt > 0) {
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p->bp = bp;
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p->cc = ep - bp;
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/*
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* See comment above about p->cc < 0.
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*/
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if (p->cc < 0)
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p->cc = 0;
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return (n);
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}
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} else {
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