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nfqws2: improve reasm overlap support

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bol-van
2025-12-08 10:35:26 +03:00
parent 378ee514c4
commit 04cb71150a
2 changed files with 13 additions and 5 deletions
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16
nfq2/conntrack.c
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@@ -394,17 +394,25 @@ bool ReasmResize(t_reassemble *reasm, size_t new_size)
if (reasm->size_present > new_size) reasm->size_present = new_size;
return true;
}
#define REASM_MAX_NEG 0x100000
bool ReasmFeed(t_reassemble *reasm, uint32_t seq, const void *payload, size_t len)
{
uint32_t dseq = seq - reasm->seq;
if (dseq && (dseq < REASM_MAX_NEG))
return false; // fail session if a gap about to appear
uint32_t neg_overlap = reasm->seq - seq;
if ((seq > reasm->seq) || (neg_overlap > reasm->size_present))
return false; // fail session if a gap about to appear or negative overlap is beyond start position
if (neg_overlap > REASM_MAX_NEG)
return false; // too big minus
size_t szcopy;
size_t szcopy, szignore;
szignore = (neg_overlap > reasm->size_present) ? neg_overlap - reasm->size_present : 0;
szcopy = reasm->size - reasm->size_present;
if (len < szcopy) szcopy = len;
if (szignore>=szcopy) return true; // everyting is before the starting pos
szcopy-=szignore;
neg_overlap-=szignore;
// in case of seq overlap new data replaces old - unix behavior
memcpy(reasm->packet + reasm->size_present - neg_overlap, payload, szcopy);
memcpy(reasm->packet + reasm->size_present - neg_overlap, payload+szignore, szcopy);
if (szcopy>neg_overlap)
{
reasm->size_present += szcopy - neg_overlap;

2
nfq2/conntrack.h
View File

@@ -43,7 +43,7 @@ typedef struct
// this structure helps to reassemble continuous packets streams. it does not support out-of-orders
typedef struct {
uint8_t *packet; // allocated for size during reassemble request. requestor must know the message size.
uint32_t seq; // current seq number. if a packet comes with an unexpected seq - it fails reassemble session.
uint32_t seq; // current seq number. if a packet comes with unsupported seq overlap - it fails reassemble session.
size_t size; // expected message size. success means that we have received exactly 'size' bytes and have them in 'packet'
size_t size_present; // how many bytes already stored in 'packet'
} t_reassemble;