tcp_fill_headers() takes a pointer to a previously computed IPv4 header
checksum to avoid recalculating it when the payload length doesn't
change, and a separate bool to skip TCP checksum computation.
Replace both parameters with a single uint32_t csum_flags that encodes:
- IP4_CSUM (bit 31): compute IPv4 header checksum from scratch
- TCP_CSUM (bit 30): compute TCP checksum
- IP4_CMASK (low 16 bits): cached IPv4 header checksum value
When IP4_CSUM is not set, the cached checksum is extracted from the low
16 bits. This is cleaner than the pointer-based approach, and also
avoids a potential dangling pointer issue: a subsequent patch makes
tcp_fill_headers() access ip4h via with_header(), which scopes it to a
temporary variable, so a pointer to ip4h->check would become invalid
after the with_header() block.
Suggested-by: David Gibson
Signed-off-by: Laurent Vivier
Reviewed-by: Jon Maloy
Reviewed-by: David Gibson
---
tcp.c | 25 +++++++++++++------------
tcp_buf.c | 23 ++++++++++++-----------
tcp_internal.h | 7 +++++--
tcp_vu.c | 28 +++++++++++++++++-----------
4 files changed, 47 insertions(+), 36 deletions(-)
diff --git a/tcp.c b/tcp.c
index 34fdd83c52b4..0a613e9f550e 100644
--- a/tcp.c
+++ b/tcp.c
@@ -940,9 +940,10 @@ static void tcp_fill_header(struct tcphdr *th,
* @th: Pointer to TCP header
* @payload: TCP payload
* @dlen: TCP payload length
- * @ip4_check: IPv4 checksum, if already known
+ * @csum_flags: TCP_CSUM if TCP checksum must be computed,
+ * IP4_CSUM if IPv4 checksum must be computed,
+ * otherwise IPv4 checksum is provided in IP4_CMASK
* @seq: Sequence number for this segment
- * @no_tcp_csum: Do not set TCP checksum
*
* Return: frame length (including L2 headers)
*/
@@ -950,8 +951,7 @@ size_t tcp_fill_headers(const struct ctx *c, struct tcp_tap_conn *conn,
struct ethhdr *eh,
struct iphdr *ip4h, struct ipv6hdr *ip6h,
struct tcphdr *th, struct iov_tail *payload,
- size_t dlen, const uint16_t *ip4_check, uint32_t seq,
- bool no_tcp_csum)
+ size_t dlen, uint32_t csum_flags, uint32_t seq)
{
const struct flowside *tapside = TAPFLOW(conn);
size_t l4len = dlen + sizeof(*th);
@@ -971,13 +971,14 @@ size_t tcp_fill_headers(const struct ctx *c, struct tcp_tap_conn *conn,
ip4h->saddr = src4->s_addr;
ip4h->daddr = dst4->s_addr;
- if (ip4_check)
- ip4h->check = *ip4_check;
- else
+ if (csum_flags & IP4_CSUM) {
ip4h->check = csum_ip4_header(l3len, IPPROTO_TCP,
*src4, *dst4);
+ } else {
+ ip4h->check = csum_flags & IP4_CMASK;
+ }
- if (!no_tcp_csum) {
+ if (csum_flags & TCP_CSUM) {
psum = proto_ipv4_header_psum(l4len, IPPROTO_TCP,
*src4, *dst4);
}
@@ -997,7 +998,7 @@ size_t tcp_fill_headers(const struct ctx *c, struct tcp_tap_conn *conn,
ip6_set_flow_lbl(ip6h, conn->sock);
- if (!no_tcp_csum) {
+ if (csum_flags & TCP_CSUM) {
psum = proto_ipv6_header_psum(l4len, IPPROTO_TCP,
&ip6h->saddr,
&ip6h->daddr);
@@ -1012,10 +1013,10 @@ size_t tcp_fill_headers(const struct ctx *c, struct tcp_tap_conn *conn,
tcp_fill_header(th, conn, seq);
- if (no_tcp_csum)
- th->check = 0;
- else
+ if (csum_flags & TCP_CSUM)
tcp_update_csum(psum, th, payload, dlen);
+ else
+ th->check = 0;
return MAX(l3len + sizeof(struct ethhdr), ETH_ZLEN);
}
diff --git a/tcp_buf.c b/tcp_buf.c
index efdd42558e15..ca356089dc0b 100644
--- a/tcp_buf.c
+++ b/tcp_buf.c
@@ -166,14 +166,15 @@ static void tcp_l2_buf_pad(struct iovec *iov)
* @c: Execution context
* @conn: Connection pointer
* @iov: Pointer to an array of iovec of TCP pre-cooked buffers
- * @check: Checksum, if already known
+ * @csum_flags: TCP_CSUM if TCP checksum must be computed,
+ * IP4_CSUM if IPv4 checksum must be computed,
+ * otherwise IPv4 checksum is provided in IP4_CMASK
* @seq: Sequence number for this segment
- * @no_tcp_csum: Do not set TCP checksum
*/
static void tcp_l2_buf_fill_headers(const struct ctx *c,
struct tcp_tap_conn *conn,
- struct iovec *iov, const uint16_t *check,
- uint32_t seq, bool no_tcp_csum)
+ struct iovec *iov, uint32_t csum_flags,
+ uint32_t seq)
{
struct iov_tail tail = IOV_TAIL(&iov[TCP_IOV_PAYLOAD], 1, 0);
struct tcphdr th_storage, *th = IOV_REMOVE_HEADER(&tail, th_storage);
@@ -191,8 +192,7 @@ static void tcp_l2_buf_fill_headers(const struct ctx *c,
ip6h = iov[TCP_IOV_IP].iov_base;
l2len = tcp_fill_headers(c, conn, eh, ip4h, ip6h, th, &tail,
- iov_tail_size(&tail), check, seq,
- no_tcp_csum);
+ iov_tail_size(&tail), csum_flags, seq);
tap_hdr_update(taph, l2len);
}
@@ -234,7 +234,7 @@ int tcp_buf_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags)
if (flags & KEEPALIVE)
seq--;
- tcp_l2_buf_fill_headers(c, conn, iov, NULL, seq, false);
+ tcp_l2_buf_fill_headers(c, conn, iov, IP4_CSUM | TCP_CSUM, seq);
tcp_l2_buf_pad(iov);
@@ -271,7 +271,7 @@ static void tcp_data_to_tap(const struct ctx *c, struct tcp_tap_conn *conn,
ssize_t dlen, int no_csum, uint32_t seq, bool push)
{
struct tcp_payload_t *payload;
- const uint16_t *check = NULL;
+ uint32_t check = IP4_CSUM;
struct iovec *iov;
conn->seq_to_tap = seq + dlen;
@@ -280,9 +280,10 @@ static void tcp_data_to_tap(const struct ctx *c, struct tcp_tap_conn *conn,
if (CONN_V4(conn)) {
if (no_csum) {
struct iovec *iov_prev = tcp_l2_iov[tcp_payload_used - 1];
- struct iphdr *iph = iov_prev[TCP_IOV_IP].iov_base;
+ const struct iphdr *iph = iov_prev[TCP_IOV_IP].iov_base;
- check = &iph->check;
+ /* overwrite IP4_CSUM flag as we set the checksum */
+ check = iph->check;
}
iov[TCP_IOV_IP] = IOV_OF_LVALUE(tcp4_payload_ip[tcp_payload_used]);
} else if (CONN_V6(conn)) {
@@ -296,7 +297,7 @@ static void tcp_data_to_tap(const struct ctx *c, struct tcp_tap_conn *conn,
payload->th.ack = 1;
payload->th.psh = push;
iov[TCP_IOV_PAYLOAD].iov_len = dlen + sizeof(struct tcphdr);
- tcp_l2_buf_fill_headers(c, conn, iov, check, seq, false);
+ tcp_l2_buf_fill_headers(c, conn, iov, TCP_CSUM | check, seq);
tcp_l2_buf_pad(iov);
diff --git a/tcp_internal.h b/tcp_internal.h
index a0fa19f4ed11..40472c9973c8 100644
--- a/tcp_internal.h
+++ b/tcp_internal.h
@@ -183,12 +183,15 @@ void tcp_rst_do(const struct ctx *c, struct tcp_tap_conn *conn);
struct tcp_info_linux;
+#define IP4_CSUM 0x80000000
+#define IP4_CMASK 0x0000FFFF
+#define TCP_CSUM 0x40000000
+
size_t tcp_fill_headers(const struct ctx *c, struct tcp_tap_conn *conn,
struct ethhdr *eh,
struct iphdr *ip4h, struct ipv6hdr *ip6h,
struct tcphdr *th, struct iov_tail *payload,
- size_t dlen, const uint16_t *ip4_check, uint32_t seq,
- bool no_tcp_csum);
+ size_t dlen, uint32_t csum_flags, uint32_t seq);
int tcp_update_seqack_wnd(const struct ctx *c, struct tcp_tap_conn *conn,
bool force_seq, struct tcp_info_linux *tinfo);
diff --git a/tcp_vu.c b/tcp_vu.c
index f6ac76e52438..65e7dfe63437 100644
--- a/tcp_vu.c
+++ b/tcp_vu.c
@@ -136,7 +136,7 @@ int tcp_vu_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags)
seq--;
tcp_fill_headers(c, conn, eh, ip4h, ip6h, th, &payload,
- optlen, NULL, seq, !*c->pcap);
+ optlen, IP4_CSUM | (*c->pcap ? TCP_CSUM : 0), seq);
vu_pad(flags_elem[0].in_sg, 1, hdrlen + optlen);
vu_flush(vdev, vq, flags_elem, 1, hdrlen + optlen);
@@ -284,13 +284,15 @@ static ssize_t tcp_vu_sock_recv(const struct ctx *c, struct vu_virtq *vq,
* @iov: Pointer to the array of IO vectors
* @iov_cnt: Number of entries in @iov
* @dlen: Data length
- * @check: Checksum, if already known
- * @no_tcp_csum: Do not set TCP checksum
+ * @csum_flags: Pointer to checksum flags (input/output)
+ * TCP_CSUM if TCP checksum must be computed,
+ * IP4_CSUM if IPv4 checksum must be computed,
+ * otherwise IPv4 checksum is provided in IP4_CMASK
* @push: Set PSH flag, last segment in a batch
*/
static void tcp_vu_prepare(const struct ctx *c, struct tcp_tap_conn *conn,
struct iovec *iov, size_t iov_cnt, size_t dlen,
- const uint16_t **check, bool no_tcp_csum, bool push)
+ uint32_t *csum_flags, bool push)
{
const struct flowside *toside = TAPFLOW(conn);
bool v6 = !(inany_v4(&toside->eaddr) && inany_v4(&toside->oaddr));
@@ -334,9 +336,11 @@ static void tcp_vu_prepare(const struct ctx *c, struct tcp_tap_conn *conn,
th->psh = push;
tcp_fill_headers(c, conn, eh, ip4h, ip6h, th, &payload, dlen,
- *check, conn->seq_to_tap, no_tcp_csum);
+ *csum_flags, conn->seq_to_tap);
+
+ /* Preserve TCP_CSUM, overwrite IP4_CSUM as we set the checksum */
if (ip4h)
- *check = &ip4h->check;
+ *csum_flags = (*csum_flags & TCP_CSUM) | ip4h->check;
}
/**
@@ -352,12 +356,11 @@ int tcp_vu_data_from_sock(const struct ctx *c, struct tcp_tap_conn *conn)
uint32_t wnd_scaled = conn->wnd_from_tap << conn->ws_from_tap;
struct vu_dev *vdev = c->vdev;
struct vu_virtq *vq = &vdev->vq[VHOST_USER_RX_QUEUE];
+ uint32_t already_sent, check;
ssize_t len, previous_dlen;
int i, iov_cnt, head_cnt;
size_t hdrlen, fillsize;
int v6 = CONN_V6(conn);
- uint32_t already_sent;
- const uint16_t *check;
if (!vu_queue_enabled(vq) || !vu_queue_started(vq)) {
debug("Got packet, but RX virtqueue not usable yet");
@@ -444,7 +447,10 @@ int tcp_vu_data_from_sock(const struct ctx *c, struct tcp_tap_conn *conn)
*/
hdrlen = tcp_vu_hdrlen(v6);
- for (i = 0, previous_dlen = -1, check = NULL; i < head_cnt; i++) {
+ check = IP4_CSUM;
+ if (*c->pcap)
+ check |= TCP_CSUM;
+ for (i = 0, previous_dlen = -1; i < head_cnt; i++) {
struct iovec *iov = &elem[head[i]].in_sg[0];
int buf_cnt = head[i + 1] - head[i];
size_t frame_size = iov_size(iov, buf_cnt);
@@ -460,10 +466,10 @@ int tcp_vu_data_from_sock(const struct ctx *c, struct tcp_tap_conn *conn)
/* The IPv4 header checksum varies only with dlen */
if (previous_dlen != dlen)
- check = NULL;
+ check |= IP4_CSUM;
previous_dlen = dlen;
- tcp_vu_prepare(c, conn, iov, buf_cnt, dlen, &check, !*c->pcap, push);
+ tcp_vu_prepare(c, conn, iov, buf_cnt, dlen, &check, push);
vu_pad(elem[head[i]].in_sg, buf_cnt, dlen + hdrlen);
vu_flush(vdev, vq, &elem[head[i]], buf_cnt, dlen + hdrlen);
--
2.54.0