Add probabilistic use of TCP_FASTOPEN and close()

Makefile

@@ -1,5 +1,5 @@
 COMP ?= clang
-DISABLED_WARNINGS ?= -Wno-padded
+DISABLED_WARNINGS ?= -Wno-padded -Wno-disabled-macro-expansion
 CFLAGS ?= -Weverything -Werror -O3 -g --std=gnu11 --pedantic-errors -fPIE -fstack-protector-strong -D_GNU_SOURCE $(DISABLED_WARNINGS)
 LDFLAGS ?= $(CFLAGS) -Wl,-z,relro -Wl,-z,now -pie
 LIBS ?=

rand.c

@@ -50,3 +50,12 @@ void rand_fill(void *value, size_t size) {
 	rand_buf.start = 0;
 	rand_buf.length = BUF_LEN_MAX;
 }
+
+bool rand_yes_no(uint64_t mean_yes_period) {
+	if (!mean_yes_period) {
+		return false;
+	}
+	uint64_t val;
+	rand_fill(&val, sizeof(val));
+	return !(val % mean_yes_period);
+}

rand.h

@@ -1,7 +1,9 @@
 #pragma once
 
+#include <stdbool.h>
 #include <stddef.h>
 
 void rand_init(void);
 void rand_cleanup(void);
 void rand_fill(void *, size_t);
+bool rand_yes_no(uint64_t);

stutterfuzz.c

@@ -30,9 +30,13 @@ static struct {
 	char *service;
 	uint32_t num_conns;
 	uint32_t cycle_ms;
+	uint32_t fastopen_chance;
+	uint32_t close_chance;
 } config = {
 	.num_conns = 100,
 	.cycle_ms = 150,
+	.fastopen_chance = 2,
+	.close_chance = 500,
 };
 
 struct file {
@@ -74,6 +78,8 @@ static bool parse_opts(int argc, char *argv[]) {
 		{"port",            required_argument, 0, 'p'},
 		{"cycle-ms",        required_argument, 0, 'c'},
 		{"num-conns",       required_argument, 0, 'n'},
+		{"fastopen-chance", required_argument, 0, 'f'},
+		{"close-chance",    required_argument, 0, 'l'},
 		{0,                 0,                 0, 0  },
 	};
 
@@ -101,6 +107,14 @@ static bool parse_opts(int argc, char *argv[]) {
 				assert(config.num_conns);
 				break;
 
+			case 'f':
+				config.fastopen_chance = (uint32_t) strtoul(optarg, NULL, 10);
+				break;
+
+			case 'l':
+				config.close_chance = (uint32_t) strtoul(optarg, NULL, 10);
+				break;
+
 			default:
 				return false;
 		}
@@ -238,12 +252,12 @@ static void conn_new() {
 	assert(conn);
 	conn->fd = socket(AF_INET6, SOCK_STREAM | SOCK_NONBLOCK, 0);
 	assert(conn->fd >= 0);
-	// TODO: consider sending data here
-	char buf[1];
-	sendto(conn->fd, buf, 0, MSG_DONTWAIT | MSG_FASTOPEN, addrs[0].ai_addr, addrs[0].ai_addrlen);
+
 	conn->file = file_next();
-	conn->start_cycle = cycle;
 	conn->offset = 0;
+	conn->offset = rand_yes_no(config.fastopen_chance) ? conn_get_split(conn) : 0;
+	sendto(conn->fd, conn->file->buf, conn->offset, MSG_DONTWAIT | MSG_FASTOPEN, addrs[0].ai_addr, addrs[0].ai_addrlen);
+	conn->start_cycle = cycle;
 	list_add(&conn->conn_list, &conn_pending_head);
 	struct epoll_event ev = {
 		.events = EPOLLOUT,
@@ -292,14 +306,27 @@ static void conn_send_message(struct conn *conn) {
 		conn_send_not_ready++;
 		return;
 	}
-	size_t remaining = conn->file->len - conn->offset;
+
+	if (conn->offset == conn->file->len) {
+		conn_del(conn);
+		return;
+	}
+
+	if (rand_yes_no(config.close_chance)) {
+		conn_del(conn);
+		return;
+	}
+
 	size_t to_send = conn_get_split(conn);
-	if (send(conn->fd, conn->file->buf + conn->offset, to_send, MSG_DONTWAIT | MSG_NOSIGNAL) != (ssize_t) to_send ||
-			to_send == remaining) {
+	if (send(conn->fd, conn->file->buf + conn->offset, to_send, MSG_DONTWAIT | MSG_NOSIGNAL) != (ssize_t) to_send) {
 		conn_del(conn);
 		return;
 	}
 	conn->offset += to_send;
+	if (conn->offset == conn->file->len) {
+		conn_del(conn);
+		return;
+	}
 }
 
 static void conn_check(struct conn *conn) {
@@ -352,6 +379,8 @@ int main(int argc, char *argv[]) {
 			"\t--port=PORT [required]\n"
 			"\t--cycle-ms=CYCLE_MILLSECONDS [default 150]\n"
 			"\t--num-conns=PARALLEL_CONNECTIONS [default 100]\n"
+			"\t--fastopen-chance=CHANCE [default 2]\n"
+			"\t--close-chance=CHANCE [default 500]\n"
 			, argv[0]);
 		exit(EXIT_FAILURE);
 	}