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udp: Preadjust udp[46]_l2_iov_tap[].iov_base for pasta mode

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Currently, we always populate udp[46]_l2_iov_tap[].iov_base with the
very start of the header buffers, including space for the qemu vnet_len
tag suitable for passt mode.  That's ok because we don't actually use these
iovecs for pasta mode.

However, we do know the mode in udp_sock[46]_iov_init() so adjust these
to the beginning of the headers we'll actually need for the mode: including
the vnet_len tag for passt, but excluding it for pasta.

This allows a slightly nicer way to locate the right buffer to send in the
pasta case, and will allow some additional cleanups later.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
David Gibson 2022-11-24 19:54:20 +11:00 committed by Stefano Brivio
parent d533807027
commit 4b2d227c86
1 changed files with 18 additions and 18 deletions
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32
udp.c
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@ -314,8 +314,9 @@ void udp_update_l2_buf(const unsigned char *eth_d, const unsigned char *eth_s,
/** /**
* udp_sock4_iov_init() - Initialise scatter-gather L2 buffers for IPv4 sockets * udp_sock4_iov_init() - Initialise scatter-gather L2 buffers for IPv4 sockets
* @c: Execution context
*/ */
static void udp_sock4_iov_init(void) static void udp_sock4_iov_init(const struct ctx *c)
{ {
struct mmsghdr *h; struct mmsghdr *h;
int i; int i;
@ -343,7 +344,11 @@ static void udp_sock4_iov_init(void)
for (i = 0, h = udp4_l2_mh_tap; i < UDP_MAX_FRAMES; i++, h++) { for (i = 0, h = udp4_l2_mh_tap; i < UDP_MAX_FRAMES; i++, h++) {
struct msghdr *mh = &h->msg_hdr; struct msghdr *mh = &h->msg_hdr;
if (c->mode == MODE_PASTA)
udp4_l2_iov_tap[i].iov_base = &udp4_l2_buf[i].eh;
else
udp4_l2_iov_tap[i].iov_base = &udp4_l2_buf[i].vnet_len; udp4_l2_iov_tap[i].iov_base = &udp4_l2_buf[i].vnet_len;
mh->msg_iov = &udp4_l2_iov_tap[i]; mh->msg_iov = &udp4_l2_iov_tap[i];
mh->msg_iovlen = 1; mh->msg_iovlen = 1;
} }
@ -351,8 +356,9 @@ static void udp_sock4_iov_init(void)
/** /**
* udp_sock6_iov_init() - Initialise scatter-gather L2 buffers for IPv6 sockets * udp_sock6_iov_init() - Initialise scatter-gather L2 buffers for IPv6 sockets
* @c: Execution context
*/ */
static void udp_sock6_iov_init(void) static void udp_sock6_iov_init(const struct ctx *c)
{ {
struct mmsghdr *h; struct mmsghdr *h;
int i; int i;
@ -383,7 +389,11 @@ static void udp_sock6_iov_init(void)
for (i = 0, h = udp6_l2_mh_tap; i < UDP_MAX_FRAMES; i++, h++) { for (i = 0, h = udp6_l2_mh_tap; i < UDP_MAX_FRAMES; i++, h++) {
struct msghdr *mh = &h->msg_hdr; struct msghdr *mh = &h->msg_hdr;
if (c->mode == MODE_PASTA)
udp6_l2_iov_tap[i].iov_base = &udp6_l2_buf[i].eh;
else
udp6_l2_iov_tap[i].iov_base = &udp6_l2_buf[i].vnet_len; udp6_l2_iov_tap[i].iov_base = &udp6_l2_buf[i].vnet_len;
mh->msg_iov = &udp6_l2_iov_tap[i]; mh->msg_iov = &udp6_l2_iov_tap[i];
mh->msg_iovlen = 1; mh->msg_iovlen = 1;
} }
@ -685,16 +695,7 @@ static void udp_sock_fill_data_v4(const struct ctx *c, int n,
b->uh.len = htons(udp4_l2_mh_sock[n].msg_len + sizeof(b->uh)); b->uh.len = htons(udp4_l2_mh_sock[n].msg_len + sizeof(b->uh));
if (c->mode == MODE_PASTA) { if (c->mode == MODE_PASTA) {
/* If we pass &b->eh directly to write(), starting from void *frame = udp4_l2_iov_tap[n].iov_base;
* gcc 12.1, at least on aarch64 and x86_64, we get a bogus
* stringop-overread warning, due to:
* https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103483
*
* but we can't disable it with a pragma, because it will be
* ignored if LTO is enabled:
* https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80922
*/
void *frame = (char *)b + offsetof(struct udp4_l2_buf_t, eh);
if (write(c->fd_tap, frame, sizeof(b->eh) + ip_len) < 0) if (write(c->fd_tap, frame, sizeof(b->eh) + ip_len) < 0)
debug("tap write: %s", strerror(errno)); debug("tap write: %s", strerror(errno));
@ -796,8 +797,7 @@ static void udp_sock_fill_data_v6(const struct ctx *c, int n,
b->ip6h.hop_limit = 255; b->ip6h.hop_limit = 255;
if (c->mode == MODE_PASTA) { if (c->mode == MODE_PASTA) {
/* See udp_sock_fill_data_v4() for the reason behind 'frame' */ void *frame = udp6_l2_iov_tap[n].iov_base;
void *frame = (char *)b + offsetof(struct udp6_l2_buf_t, eh);
if (write(c->fd_tap, frame, sizeof(b->eh) + ip_len) < 0) if (write(c->fd_tap, frame, sizeof(b->eh) + ip_len) < 0)
debug("tap write: %s", strerror(errno)); debug("tap write: %s", strerror(errno));
@ -1231,10 +1231,10 @@ static void udp_splice_iov_init(void)
int udp_init(struct ctx *c) int udp_init(struct ctx *c)
{ {
if (c->ifi4) if (c->ifi4)
udp_sock4_iov_init(); udp_sock4_iov_init(c);
if (c->ifi6) if (c->ifi6)
udp_sock6_iov_init(); udp_sock6_iov_init(c);
udp_invert_portmap(&c->udp.fwd_in); udp_invert_portmap(&c->udp.fwd_in);
udp_invert_portmap(&c->udp.fwd_out); udp_invert_portmap(&c->udp.fwd_out);