From 0dacea92d26c31d453c58de2e99c178fee554166 Mon Sep 17 00:00:00 2001 From: Ed Swierk Date: Thu, 16 Nov 2017 06:06:06 -0800 Subject: net: Transmit zero UDP checksum as 0xFFFF The checksum algorithm used by IPv4, TCP and UDP allows a zero value to be represented by either 0x0000 and 0xFFFF. But per RFC 768, a zero UDP checksum must be transmitted as 0xFFFF because 0x0000 is a special value meaning no checksum. Substitute 0xFFFF whenever a checksum is computed as zero when modifying a UDP datagram header. Doing this on IPv4 and TCP checksums is unnecessary but legal. Add a wrapper for net_checksum_finish() that makes the substitution. (We can't just change net_checksum_finish(), as that function is also used by receivers to verify checksums, and in that case the expected value is always 0x0000.) Signed-off-by: Ed Swierk Signed-off-by: Jason Wang --- hw/net/net_tx_pkt.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'hw/net/net_tx_pkt.c') diff --git a/hw/net/net_tx_pkt.c b/hw/net/net_tx_pkt.c index 20b25496e5..e29c881bc2 100644 --- a/hw/net/net_tx_pkt.c +++ b/hw/net/net_tx_pkt.c @@ -486,7 +486,7 @@ static void net_tx_pkt_do_sw_csum(struct NetTxPkt *pkt) net_checksum_add_iov(iov, iov_len, pkt->virt_hdr.csum_start, csl, cso); /* Put the checksum obtained into the packet */ - csum = cpu_to_be16(net_checksum_finish(csum_cntr)); + csum = cpu_to_be16(net_checksum_finish_nozero(csum_cntr)); iov_from_buf(iov, iov_len, csum_offset, &csum, sizeof csum); } -- cgit v1.2.3-55-g7522