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icmp: fix checksum on replies of echo request with ID 0, sequence 0 and either no data or any amount of 0x00 Bytes as data (closes: #45322)

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When a client sends an ICMP echo request with ID 0, sequence 0 and
either no data or any amount of 0x00 bytes as data, the checksum in the
reply is wrong (off-by-one).

Expected checksum is 0xffff in that case, observed is 0x0000.
This commit is contained in:
tabascoeye 2015-06-15 15:53:14 +02:00 committed by Sylvain Rochet
parent 232cf8c28b
commit 7856141fc4
1 changed files with 1 additions and 1 deletions
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2
src/core/ipv4/icmp.c
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@ -196,7 +196,7 @@ icmp_input(struct pbuf *p, struct netif *inp)
ICMPH_TYPE_SET(iecho, ICMP_ER);
#if CHECKSUM_GEN_ICMP
/* adjust the checksum */
if (iecho->chksum >= PP_HTONS(0xffffU - (ICMP_ECHO << 8))) {
if (iecho->chksum > PP_HTONS(0xffffU - (ICMP_ECHO << 8))) {
iecho->chksum += PP_HTONS(ICMP_ECHO << 8) + 1;
} else {
iecho->chksum += PP_HTONS(ICMP_ECHO << 8);