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Diffstat (limited to 'tap.c')
-rw-r--r--tap.c106
1 files changed, 90 insertions, 16 deletions
diff --git a/tap.c b/tap.c
index 4541f51..6db5d88 100644
--- a/tap.c
+++ b/tap.c
@@ -62,14 +62,67 @@
#include "vhost_user.h"
#include "vu_common.h"
+/* Maximum allowed frame lengths (including L2 header) */
+
+/* Verify that an L2 frame length limit is large enough to contain the header,
+ * but small enough to fit in the packet pool
+ */
+#define CHECK_FRAME_LEN(len) \
+ static_assert((len) >= ETH_HLEN && (len) <= PACKET_MAX_LEN, \
+ #len " has bad value")
+
+CHECK_FRAME_LEN(L2_MAX_LEN_PASTA);
+CHECK_FRAME_LEN(L2_MAX_LEN_PASST);
+CHECK_FRAME_LEN(L2_MAX_LEN_VU);
+
+/* We try size the packet pools so that we can use a single batch for the entire
+ * packet buffer. This might be exceeded for vhost-user, though, which uses its
+ * own buffers rather than pkt_buf.
+ *
+ * This is just a tuning parameter, the code will work with slightly more
+ * overhead if it's incorrect. So, we estimate based on the minimum practical
+ * frame size - an empty UDP datagram - rather than the minimum theoretical
+ * frame size.
+ *
+ * FIXME: Profile to work out how big this actually needs to be to amortise
+ * per-batch syscall overheads
+ */
+#define TAP_MSGS_IP4 \
+ DIV_ROUND_UP(sizeof(pkt_buf), \
+ ETH_HLEN + sizeof(struct iphdr) + sizeof(struct udphdr))
+#define TAP_MSGS_IP6 \
+ DIV_ROUND_UP(sizeof(pkt_buf), \
+ ETH_HLEN + sizeof(struct ipv6hdr) + sizeof(struct udphdr))
+
/* IPv4 (plus ARP) and IPv6 message batches from tap/guest to IP handlers */
-static PACKET_POOL_NOINIT(pool_tap4, TAP_MSGS, pkt_buf);
-static PACKET_POOL_NOINIT(pool_tap6, TAP_MSGS, pkt_buf);
+static PACKET_POOL_NOINIT(pool_tap4, TAP_MSGS_IP4, pkt_buf);
+static PACKET_POOL_NOINIT(pool_tap6, TAP_MSGS_IP6, pkt_buf);
#define TAP_SEQS 128 /* Different L4 tuples in one batch */
#define FRAGMENT_MSG_RATE 10 /* # seconds between fragment warnings */
/**
+ * tap_l2_max_len() - Maximum frame size (including L2 header) for current mode
+ * @c: Execution context
+ */
+unsigned long tap_l2_max_len(const struct ctx *c)
+{
+ /* NOLINTBEGIN(bugprone-branch-clone): values can be the same */
+ switch (c->mode) {
+ case MODE_PASST:
+ return L2_MAX_LEN_PASST;
+ case MODE_PASTA:
+ return L2_MAX_LEN_PASTA;
+ case MODE_VU:
+ return L2_MAX_LEN_VU;
+ }
+ /* NOLINTEND(bugprone-branch-clone) */
+ ASSERT(0);
+
+ return 0; /* Unreachable, for cppcheck's sake */
+}
+
+/**
* tap_send_single() - Send a single frame
* @c: Execution context
* @data: Packet buffer
@@ -508,6 +561,7 @@ PACKET_POOL_DECL(pool_l4, UIO_MAXIOV, pkt_buf);
* struct l4_seq4_t - Message sequence for one protocol handler call, IPv4
* @msgs: Count of messages in sequence
* @protocol: Protocol number
+ * @ttl: Time to live
* @source: Source port
* @dest: Destination port
* @saddr: Source address
@@ -516,6 +570,7 @@ PACKET_POOL_DECL(pool_l4, UIO_MAXIOV, pkt_buf);
*/
static struct tap4_l4_t {
uint8_t protocol;
+ uint8_t ttl;
uint16_t source;
uint16_t dest;
@@ -535,6 +590,7 @@ static struct tap4_l4_t {
* @dest: Destination port
* @saddr: Source address
* @daddr: Destination address
+ * @hop_limit: Hop limit
* @msg: Array of messages that can be handled in a single call
*/
static struct tap6_l4_t {
@@ -547,6 +603,8 @@ static struct tap6_l4_t {
struct in6_addr saddr;
struct in6_addr daddr;
+ uint8_t hop_limit;
+
struct pool_l4_t p;
} tap6_l4[TAP_SEQS /* Arbitrary: TAP_MSGS in theory, so limit in users */];
@@ -735,7 +793,8 @@ resume:
#define L4_MATCH(iph, uh, seq) \
((seq)->protocol == (iph)->protocol && \
(seq)->source == (uh)->source && (seq)->dest == (uh)->dest && \
- (seq)->saddr.s_addr == (iph)->saddr && (seq)->daddr.s_addr == (iph)->daddr)
+ (seq)->saddr.s_addr == (iph)->saddr && \
+ (seq)->daddr.s_addr == (iph)->daddr && (seq)->ttl == (iph)->ttl)
#define L4_SET(iph, uh, seq) \
do { \
@@ -744,6 +803,7 @@ resume:
(seq)->dest = (uh)->dest; \
(seq)->saddr.s_addr = (iph)->saddr; \
(seq)->daddr.s_addr = (iph)->daddr; \
+ (seq)->ttl = (iph)->ttl; \
} while (0)
if (seq && L4_MATCH(iph, uh, seq) && seq->p.count < UIO_MAXIOV)
@@ -792,7 +852,7 @@ append:
for (k = 0; k < p->count; )
k += udp_tap_handler(c, PIF_TAP, AF_INET,
&seq->saddr, &seq->daddr,
- p, k, now);
+ seq->ttl, p, k, now);
}
}
@@ -915,7 +975,8 @@ resume:
(seq)->dest == (uh)->dest && \
(seq)->flow_lbl == ip6_get_flow_lbl(ip6h) && \
IN6_ARE_ADDR_EQUAL(&(seq)->saddr, saddr) && \
- IN6_ARE_ADDR_EQUAL(&(seq)->daddr, daddr))
+ IN6_ARE_ADDR_EQUAL(&(seq)->daddr, daddr) && \
+ (seq)->hop_limit == (ip6h)->hop_limit)
#define L4_SET(ip6h, proto, uh, seq) \
do { \
@@ -925,6 +986,7 @@ resume:
(seq)->flow_lbl = ip6_get_flow_lbl(ip6h); \
(seq)->saddr = *saddr; \
(seq)->daddr = *daddr; \
+ (seq)->hop_limit = (ip6h)->hop_limit; \
} while (0)
if (seq && L4_MATCH(ip6h, proto, uh, seq) &&
@@ -975,7 +1037,7 @@ append:
for (k = 0; k < p->count; )
k += udp_tap_handler(c, PIF_TAP, AF_INET6,
&seq->saddr, &seq->daddr,
- p, k, now);
+ seq->hop_limit, p, k, now);
}
}
@@ -1010,8 +1072,10 @@ void tap_handler(struct ctx *c, const struct timespec *now)
* @c: Execution context
* @l2len: Total L2 packet length
* @p: Packet buffer
+ * @now: Current timestamp
*/
-void tap_add_packet(struct ctx *c, ssize_t l2len, char *p)
+void tap_add_packet(struct ctx *c, ssize_t l2len, char *p,
+ const struct timespec *now)
{
const struct ethhdr *eh;
@@ -1027,9 +1091,17 @@ void tap_add_packet(struct ctx *c, ssize_t l2len, char *p)
switch (ntohs(eh->h_proto)) {
case ETH_P_ARP:
case ETH_P_IP:
+ if (pool_full(pool_tap4)) {
+ tap4_handler(c, pool_tap4, now);
+ pool_flush(pool_tap4);
+ }
packet_add(pool_tap4, l2len, p);
break;
case ETH_P_IPV6:
+ if (pool_full(pool_tap6)) {
+ tap6_handler(c, pool_tap6, now);
+ pool_flush(pool_tap6);
+ }
packet_add(pool_tap6, l2len, p);
break;
default:
@@ -1080,7 +1152,7 @@ static void tap_passt_input(struct ctx *c, const struct timespec *now)
do {
n = recv(c->fd_tap, pkt_buf + partial_len,
- TAP_BUF_BYTES - partial_len, MSG_DONTWAIT);
+ sizeof(pkt_buf) - partial_len, MSG_DONTWAIT);
} while ((n < 0) && errno == EINTR);
if (n < 0) {
@@ -1097,7 +1169,7 @@ static void tap_passt_input(struct ctx *c, const struct timespec *now)
while (n >= (ssize_t)sizeof(uint32_t)) {
uint32_t l2len = ntohl_unaligned(p);
- if (l2len < sizeof(struct ethhdr) || l2len > ETH_MAX_MTU) {
+ if (l2len < sizeof(struct ethhdr) || l2len > L2_MAX_LEN_PASST) {
err("Bad frame size from guest, resetting connection");
tap_sock_reset(c);
return;
@@ -1110,7 +1182,7 @@ static void tap_passt_input(struct ctx *c, const struct timespec *now)
p += sizeof(uint32_t);
n -= sizeof(uint32_t);
- tap_add_packet(c, l2len, p);
+ tap_add_packet(c, l2len, p, now);
p += l2len;
n -= l2len;
@@ -1151,8 +1223,10 @@ static void tap_pasta_input(struct ctx *c, const struct timespec *now)
tap_flush_pools();
- for (n = 0; n <= (ssize_t)(TAP_BUF_BYTES - ETH_MAX_MTU); n += len) {
- len = read(c->fd_tap, pkt_buf + n, ETH_MAX_MTU);
+ for (n = 0;
+ n <= (ssize_t)(sizeof(pkt_buf) - L2_MAX_LEN_PASTA);
+ n += len) {
+ len = read(c->fd_tap, pkt_buf + n, L2_MAX_LEN_PASTA);
if (len == 0) {
die("EOF on tap device, exiting");
@@ -1170,10 +1244,10 @@ static void tap_pasta_input(struct ctx *c, const struct timespec *now)
/* Ignore frames of bad length */
if (len < (ssize_t)sizeof(struct ethhdr) ||
- len > (ssize_t)ETH_MAX_MTU)
+ len > (ssize_t)L2_MAX_LEN_PASTA)
continue;
- tap_add_packet(c, len, pkt_buf + n);
+ tap_add_packet(c, len, pkt_buf + n, now);
}
tap_handler(c, now);
@@ -1371,8 +1445,8 @@ void tap_sock_update_pool(void *base, size_t size)
{
int i;
- pool_tap4_storage = PACKET_INIT(pool_tap4, TAP_MSGS, base, size);
- pool_tap6_storage = PACKET_INIT(pool_tap6, TAP_MSGS, base, size);
+ pool_tap4_storage = PACKET_INIT(pool_tap4, TAP_MSGS_IP4, base, size);
+ pool_tap6_storage = PACKET_INIT(pool_tap6, TAP_MSGS_IP6, base, size);
for (i = 0; i < TAP_SEQS; i++) {
tap4_l4[i].p = PACKET_INIT(pool_l4, UIO_MAXIOV, base, size);
generated by cgit v1.2.3 (git 2.25.1) at 2025-07-02 11:33:09 +0000