From: David Gibson <david@gibson.dropbear.id.au>
To: Stefano Brivio <sbrivio@redhat.com>
Cc: passt-dev@passt.top
Subject: Re: [PATCH 5/7] udp: Share payload buffers between IPv4 and IPv6
Date: Wed, 1 May 2024 12:46:10 +1000 [thread overview]
Message-ID: <ZjGs8nZKowBfIUvZ@zatzit> (raw)
In-Reply-To: <20240430221604.247fb543@elisabeth>
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On Tue, Apr 30, 2024 at 10:16:04PM +0200, Stefano Brivio wrote:
> On Tue, 30 Apr 2024 20:05:39 +1000
> David Gibson <david@gibson.dropbear.id.au> wrote:
>
> > Currently the IPv4 and IPv6 paths unnecessarily use different buffers for
> > the UDP payload. Now that we're handling the various pieces of the UDP
> > packets with an iov, we can split the payload part of the buffers off into
> > its own array shared between IPv4 and IPv6. As well as saving a little
> > memory, this allows the payload buffers to be neatly page aligned.
> >
> > With the buffers merged, udp[46]_l2_iov_sock contain exactly the same thing
> > as each other and can also be merged. Likewise udp[46]_iov_splice can be
> > merged together.
> >
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> > udp.c | 127 ++++++++++++++++++++++++++++++----------------------------
> > 1 file changed, 65 insertions(+), 62 deletions(-)
> >
> > diff --git a/udp.c b/udp.c
> > index 86d0419f..8c726056 100644
> > --- a/udp.c
> > +++ b/udp.c
> > @@ -171,14 +171,22 @@ static uint8_t udp_act[IP_VERSIONS][UDP_ACT_TYPE_MAX][DIV_ROUND_UP(NUM_PORTS, 8)
> >
> > /* Static buffers */
> >
> > +static struct udp_payload {
>
> As we're defining a new struct, the usual comment format would be nice,
> and I would also keep it symmetric with tcp_payload_t (udp_payload_t),
> say:
>
> /**
> * struct udp_payload_t - UDP header and data for inbound messages
> * @uh: UDP header
> * @data: UDP data
> */
>
> > + struct udphdr uh;
> > + char data[USHRT_MAX - sizeof(struct udphdr)];
> > +#ifdef __AVX2__
> > +} __attribute__ ((packed, aligned(32)))
> > +#else
> > +} __attribute__ ((packed, aligned(__alignof__(unsigned int))))
> > +#endif
> > +udp_payload_buf[UDP_MAX_FRAMES];
>
> ...and this could be 'udp_payload'.
Amended as suggested.
> > +
> > /**
> > * udp4_l2_buf_t - Pre-cooked IPv4 packet buffers for tap connections
> > * @s_in: Source socket address, filled in by recvmmsg()
> > * @taph: Tap backend specific header
> > * @eh: Prefilled ethernet header
> > * @iph: Pre-filled IP header (except for tot_len and saddr)
> > - * @uh: Headroom for UDP header
> > - * @data: Storage for UDP payload
> > */
> > static struct udp4_l2_buf_t {
> > struct sockaddr_in s_in;
> > @@ -186,9 +194,6 @@ static struct udp4_l2_buf_t {
> > struct tap_hdr taph;
> > struct ethhdr eh;
> > struct iphdr iph;
> > - struct udphdr uh;
> > - uint8_t data[USHRT_MAX -
> > - (sizeof(struct iphdr) + sizeof(struct udphdr))];
> > } __attribute__ ((packed, aligned(__alignof__(unsigned int))))
> > udp4_l2_buf[UDP_MAX_FRAMES];
> >
> > @@ -198,8 +203,6 @@ udp4_l2_buf[UDP_MAX_FRAMES];
> > * @taph: Tap backend specific header
> > * @eh: Pre-filled ethernet header
> > * @ip6h: Pre-filled IP header (except for payload_len and addresses)
> > - * @uh: Headroom for UDP header
> > - * @data: Storage for UDP payload
> > */
> > struct udp6_l2_buf_t {
> > struct sockaddr_in6 s_in6;
> > @@ -212,9 +215,6 @@ struct udp6_l2_buf_t {
> > struct tap_hdr taph;
> > struct ethhdr eh;
> > struct ipv6hdr ip6h;
> > - struct udphdr uh;
> > - uint8_t data[USHRT_MAX -
> > - (sizeof(struct ipv6hdr) + sizeof(struct udphdr))];
> > #ifdef __AVX2__
> > } __attribute__ ((packed, aligned(32)))
> > #else
> > @@ -239,8 +239,7 @@ enum udp_iov_idx {
> > };
> >
> > /* recvmmsg()/sendmmsg() data for tap */
> > -static struct iovec udp4_l2_iov_sock [UDP_MAX_FRAMES];
> > -static struct iovec udp6_l2_iov_sock [UDP_MAX_FRAMES];
> > +static struct iovec udp_l2_iov_sock [UDP_MAX_FRAMES];
> >
> > static struct iovec udp4_l2_iov_tap [UDP_MAX_FRAMES][UDP_NUM_IOVS];
> > static struct iovec udp6_l2_iov_tap [UDP_MAX_FRAMES][UDP_NUM_IOVS];
> > @@ -249,8 +248,7 @@ static struct mmsghdr udp4_l2_mh_sock [UDP_MAX_FRAMES];
> > static struct mmsghdr udp6_l2_mh_sock [UDP_MAX_FRAMES];
> >
> > /* recvmmsg()/sendmmsg() data for "spliced" connections */
> > -static struct iovec udp4_iov_splice [UDP_MAX_FRAMES];
> > -static struct iovec udp6_iov_splice [UDP_MAX_FRAMES];
> > +static struct iovec udp_iov_splice [UDP_MAX_FRAMES];
> >
> > static struct sockaddr_in udp4_localname = {
> > .sin_family = AF_INET,
> > @@ -261,8 +259,8 @@ static struct sockaddr_in6 udp6_localname = {
> > .sin6_addr = IN6ADDR_LOOPBACK_INIT,
> > };
> >
> > -static struct mmsghdr udp4_mh_splice [UDP_MAX_FRAMES];
> > -static struct mmsghdr udp6_mh_splice [UDP_MAX_FRAMES];
> > +static struct mmsghdr udp4_mh_splice [UDP_MAX_FRAMES];
> > +static struct mmsghdr udp6_mh_splice [UDP_MAX_FRAMES];
> >
> > /**
> > * udp_portmap_clear() - Clear UDP port map before configuration
> > @@ -322,10 +320,14 @@ void udp_update_l2_buf(const unsigned char *eth_d, const unsigned char *eth_s)
> > */
> > static void udp_iov_init_one(const struct ctx *c, size_t i)
> > {
> > + struct udp_payload *payload = &udp_payload_buf[i];
> > + struct iovec *siov = &udp_l2_iov_sock[i];
> > +
> > + *siov = IOV_OF_LVALUE(payload->data);
> > +
> > if (c->ifi4) {
> > struct msghdr *mh = &udp4_l2_mh_sock[i].msg_hdr;
> > struct udp4_l2_buf_t *buf = &udp4_l2_buf[i];
> > - struct iovec *siov = &udp4_l2_iov_sock[i];
> > struct iovec *tiov = udp4_l2_iov_tap[i];
> >
> > *buf = (struct udp4_l2_buf_t) {
> > @@ -333,8 +335,6 @@ static void udp_iov_init_one(const struct ctx *c, size_t i)
> > .iph = L2_BUF_IP4_INIT(IPPROTO_UDP)
> > };
> >
> > - *siov = IOV_OF_LVALUE(buf->data);
> > -
> > mh->msg_name = &buf->s_in;
> > mh->msg_namelen = sizeof(buf->s_in);
> > mh->msg_iov = siov;
> > @@ -343,13 +343,12 @@ static void udp_iov_init_one(const struct ctx *c, size_t i)
> > tiov[UDP_IOV_TAP] = tap_hdr_iov(c, &buf->taph);
> > tiov[UDP_IOV_ETH] = IOV_OF_LVALUE(buf->eh);
> > tiov[UDP_IOV_IP] = IOV_OF_LVALUE(buf->iph);
> > - tiov[UDP_IOV_PAYLOAD].iov_base = &buf->uh;
> > + tiov[UDP_IOV_PAYLOAD].iov_base = payload;
> > }
> >
> > if (c->ifi6) {
> > struct msghdr *mh = &udp6_l2_mh_sock[i].msg_hdr;
> > struct udp6_l2_buf_t *buf = &udp6_l2_buf[i];
> > - struct iovec *siov = &udp6_l2_iov_sock[i];
> > struct iovec *tiov = udp6_l2_iov_tap[i];
> >
> > *buf = (struct udp6_l2_buf_t) {
> > @@ -357,8 +356,6 @@ static void udp_iov_init_one(const struct ctx *c, size_t i)
> > .ip6h = L2_BUF_IP6_INIT(IPPROTO_UDP)
> > };
> >
> > - *siov = IOV_OF_LVALUE(buf->data);
> > -
> > mh->msg_name = &buf->s_in6;
> > mh->msg_namelen = sizeof(buf->s_in6);
> > mh->msg_iov = siov;
> > @@ -367,7 +364,7 @@ static void udp_iov_init_one(const struct ctx *c, size_t i)
> > tiov[UDP_IOV_TAP] = tap_hdr_iov(c, &buf->taph);
> > tiov[UDP_IOV_ETH] = IOV_OF_LVALUE(buf->eh);
> > tiov[UDP_IOV_IP] = IOV_OF_LVALUE(buf->ip6h);
> > - tiov[UDP_IOV_PAYLOAD].iov_base = &buf->uh;
> > + tiov[UDP_IOV_PAYLOAD].iov_base = payload;
> > }
> > }
> >
> > @@ -581,22 +578,24 @@ static void udp_splice_sendfrom(const struct ctx *c, unsigned start, unsigned n,
> > /**
> > * udp_update_hdr4() - Update headers for one IPv4 datagram
> > * @c: Execution context
> > - * @b: Pointer to udp4_l2_buf to update
> > + * @bh: Pointer to udp4_l2_buf to update
> > + * @bp: Pointer to udp_payload to update
> > * @dstport: Destination port number
> > * @plen: Length of UDP payload
> > * @now: Current timestamp
> > *
> > * Return: size of IPv4 payload (UDP header + data)
> > */
> > -static size_t udp_update_hdr4(const struct ctx *c, struct udp4_l2_buf_t *b,
> > +static size_t udp_update_hdr4(const struct ctx *c,
> > + struct udp4_l2_buf_t *bh, struct udp_payload *bp,
> > in_port_t dstport, size_t plen,
> > const struct timespec *now)
> > {
> > + in_port_t srcport = ntohs(bh->s_in.sin_port);
> > const struct in_addr dst = c->ip4.addr_seen;
> > - size_t l4len = plen + sizeof(b->uh);
> > - size_t l3len = l4len + sizeof(b->iph);
> > - in_port_t srcport = ntohs(b->s_in.sin_port);
> > - struct in_addr src = b->s_in.sin_addr;
> > + struct in_addr src = bh->s_in.sin_addr;
> > + size_t l4len = plen + sizeof(bp->uh);
> > + size_t l3len = l4len + sizeof(bh->iph);
> >
> > if (!IN4_IS_ADDR_UNSPECIFIED(&c->ip4.dns_match) &&
> > IN4_ARE_ADDR_EQUAL(&src, &c->ip4.dns_host) && srcport == 53 &&
> > @@ -617,39 +616,41 @@ static size_t udp_update_hdr4(const struct ctx *c, struct udp4_l2_buf_t *b,
> > src = c->ip4.gw;
> > }
> >
> > - b->iph.tot_len = htons(l3len);
> > - b->iph.daddr = dst.s_addr;
> > - b->iph.saddr = src.s_addr;
> > - b->iph.check = csum_ip4_header(b->iph.tot_len, IPPROTO_UDP,
> > - src, c->ip4.addr_seen);
> > + bh->iph.tot_len = htons(l3len);
> > + bh->iph.daddr = c->ip4.addr_seen.s_addr;
>
> This is still the same as dst.s_addr (existing assignment), right?
Ah, yes, I think that's a leftover from some interim version.
Spurious change removed.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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next prev parent reply other threads:[~2024-05-01 2:54 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-30 10:05 [PATCH 0/7] Rework UDP buffers David Gibson
2024-04-30 10:05 ` [PATCH 1/7] test: Allow sftp via vsock-ssh in tests David Gibson
2024-04-30 10:05 ` [PATCH 2/7] udp: Split tap-bound UDP packets into multiple buffers using io vector David Gibson
2024-04-30 20:15 ` Stefano Brivio
2024-05-01 2:35 ` David Gibson
2024-04-30 10:05 ` [PATCH 3/7] udp: Combine initialisation of IPv4 and IPv6 iovs David Gibson
2024-04-30 10:05 ` [PATCH 4/7] udp: Explicitly set checksum in guest-bound UDP headers David Gibson
2024-04-30 10:05 ` [PATCH 5/7] udp: Share payload buffers between IPv4 and IPv6 David Gibson
2024-04-30 20:16 ` Stefano Brivio
2024-05-01 2:46 ` David Gibson [this message]
2024-04-30 10:05 ` [PATCH 6/7] udp: Use the same buffer for the L2 header for all frames David Gibson
2024-04-30 10:05 ` [PATCH 7/7] udp: Single buffer for IPv4, IPv6 headers and metadata David Gibson
2024-04-30 20:16 ` Stefano Brivio
2024-05-01 2:54 ` David Gibson
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