| Message ID | 1510841166-40615-1-git-send-email-eswierk@skyportsystems.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 2017年11月16日 22:06, Ed Swierk wrote: > 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 <eswierk@skyportsystems.com> > --- > v3: > > (Reposted to fix patch format) > > Leave net_tx_pkt_update_ip_checksums() alone since it's only computing > a partial sum of the IP pseudo-header. > > Rename wrapper to net_checksum_finish_nozero() for clarity. > > v2: > > Add a wrapper net_checksum_finish_hdr() rather than duplicating the > logic at every caller. > --- > hw/net/e1000.c | 2 +- > hw/net/net_rx_pkt.c | 2 +- > hw/net/net_tx_pkt.c | 2 +- > hw/net/vmxnet3.c | 3 ++- > include/net/checksum.h | 6 ++++++ > 5 files changed, 11 insertions(+), 4 deletions(-) > > diff --git a/hw/net/e1000.c b/hw/net/e1000.c > index 72a92be..804ec08 100644 > --- a/hw/net/e1000.c > +++ b/hw/net/e1000.c > @@ -506,7 +506,7 @@ putsum(uint8_t *data, uint32_t n, uint32_t sloc, uint32_t css, uint32_t cse) > n = cse + 1; > if (sloc < n-1) { > sum = net_checksum_add(n-css, data+css); > - stw_be_p(data + sloc, net_checksum_finish(sum)); > + stw_be_p(data + sloc, net_checksum_finish_nozero(sum)); > } > } > > diff --git a/hw/net/net_rx_pkt.c b/hw/net/net_rx_pkt.c > index cef1c2e..98a5030 100644 > --- a/hw/net/net_rx_pkt.c > +++ b/hw/net/net_rx_pkt.c > @@ -518,7 +518,7 @@ _net_rx_pkt_calc_l4_csum(struct NetRxPkt *pkt) > cntr += net_checksum_add_iov(pkt->vec, pkt->vec_len, > pkt->l4hdr_off, csl, cso); > > - csum = net_checksum_finish(cntr); > + csum = net_checksum_finish_nozero(cntr); > > trace_net_rx_pkt_l4_csum_calc_csum(pkt->l4hdr_off, csl, cntr, csum); > > diff --git a/hw/net/net_tx_pkt.c b/hw/net/net_tx_pkt.c > index 20b2549..e29c881 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); > } > > diff --git a/hw/net/vmxnet3.c b/hw/net/vmxnet3.c > index 8c4bae5..cdc307d 100644 > --- a/hw/net/vmxnet3.c > +++ b/hw/net/vmxnet3.c > @@ -972,7 +972,8 @@ static void vmxnet3_rx_need_csum_calculate(struct NetRxPkt *pkt, > data = (uint8_t *)pkt_data + vhdr->csum_start; > len = pkt_len - vhdr->csum_start; > /* Put the checksum obtained into the packet */ > - stw_be_p(data + vhdr->csum_offset, net_raw_checksum(data, len)); > + stw_be_p(data + vhdr->csum_offset, > + net_checksum_finish_nozero(net_checksum_add(len, data))); > > vhdr->flags &= ~VIRTIO_NET_HDR_F_NEEDS_CSUM; > vhdr->flags |= VIRTIO_NET_HDR_F_DATA_VALID; > diff --git a/include/net/checksum.h b/include/net/checksum.h > index 7df472c..05a0d27 100644 > --- a/include/net/checksum.h > +++ b/include/net/checksum.h > @@ -34,6 +34,12 @@ net_checksum_add(int len, uint8_t *buf) > } > > static inline uint16_t > +net_checksum_finish_nozero(uint32_t sum) > +{ > + return net_checksum_finish(sum) ?: 0xFFFF; > +} > + > +static inline uint16_t > net_raw_checksum(uint8_t *data, int length) > { > return net_checksum_finish(net_checksum_add(length, data)); Applied, thanks.
diff --git a/hw/net/e1000.c b/hw/net/e1000.c index 72a92be..804ec08 100644 --- a/hw/net/e1000.c +++ b/hw/net/e1000.c @@ -506,7 +506,7 @@ putsum(uint8_t *data, uint32_t n, uint32_t sloc, uint32_t css, uint32_t cse) n = cse + 1; if (sloc < n-1) { sum = net_checksum_add(n-css, data+css); - stw_be_p(data + sloc, net_checksum_finish(sum)); + stw_be_p(data + sloc, net_checksum_finish_nozero(sum)); } } diff --git a/hw/net/net_rx_pkt.c b/hw/net/net_rx_pkt.c index cef1c2e..98a5030 100644 --- a/hw/net/net_rx_pkt.c +++ b/hw/net/net_rx_pkt.c @@ -518,7 +518,7 @@ _net_rx_pkt_calc_l4_csum(struct NetRxPkt *pkt) cntr += net_checksum_add_iov(pkt->vec, pkt->vec_len, pkt->l4hdr_off, csl, cso); - csum = net_checksum_finish(cntr); + csum = net_checksum_finish_nozero(cntr); trace_net_rx_pkt_l4_csum_calc_csum(pkt->l4hdr_off, csl, cntr, csum); diff --git a/hw/net/net_tx_pkt.c b/hw/net/net_tx_pkt.c index 20b2549..e29c881 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); } diff --git a/hw/net/vmxnet3.c b/hw/net/vmxnet3.c index 8c4bae5..cdc307d 100644 --- a/hw/net/vmxnet3.c +++ b/hw/net/vmxnet3.c @@ -972,7 +972,8 @@ static void vmxnet3_rx_need_csum_calculate(struct NetRxPkt *pkt, data = (uint8_t *)pkt_data + vhdr->csum_start; len = pkt_len - vhdr->csum_start; /* Put the checksum obtained into the packet */ - stw_be_p(data + vhdr->csum_offset, net_raw_checksum(data, len)); + stw_be_p(data + vhdr->csum_offset, + net_checksum_finish_nozero(net_checksum_add(len, data))); vhdr->flags &= ~VIRTIO_NET_HDR_F_NEEDS_CSUM; vhdr->flags |= VIRTIO_NET_HDR_F_DATA_VALID; diff --git a/include/net/checksum.h b/include/net/checksum.h index 7df472c..05a0d27 100644 --- a/include/net/checksum.h +++ b/include/net/checksum.h @@ -34,6 +34,12 @@ net_checksum_add(int len, uint8_t *buf) } static inline uint16_t +net_checksum_finish_nozero(uint32_t sum) +{ + return net_checksum_finish(sum) ?: 0xFFFF; +} + +static inline uint16_t net_raw_checksum(uint8_t *data, int length) { return net_checksum_finish(net_checksum_add(length, data));
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 <eswierk@skyportsystems.com> --- v3: (Reposted to fix patch format) Leave net_tx_pkt_update_ip_checksums() alone since it's only computing a partial sum of the IP pseudo-header. Rename wrapper to net_checksum_finish_nozero() for clarity. v2: Add a wrapper net_checksum_finish_hdr() rather than duplicating the logic at every caller. --- hw/net/e1000.c | 2 +- hw/net/net_rx_pkt.c | 2 +- hw/net/net_tx_pkt.c | 2 +- hw/net/vmxnet3.c | 3 ++- include/net/checksum.h | 6 ++++++ 5 files changed, 11 insertions(+), 4 deletions(-)