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948def4a | 1 | /* SPDX-License-Identifier: LGPL-2.1-or-later */ |
80710ade LP |
2 | |
3 | #include "resolved-socket-graveyard.h" | |
4 | ||
5 | #define SOCKET_GRAVEYARD_USEC (5 * USEC_PER_SEC) | |
6 | #define SOCKET_GRAVEYARD_MAX 100 | |
7 | ||
8 | /* This implements a socket "graveyard" for UDP sockets. If a socket fd is added to the graveyard it is kept | |
9 | * open for a couple of more seconds, expecting one reply. Once the reply is received the fd is closed | |
10 | * immediately, or if none is received it is closed after the timeout. Why all this? So that if we contact a | |
11 | * DNS server, and it doesn't reply instantly, and we lose interest in the response and thus close the fd, we | |
12 | * don't end up sending back an ICMP error once the server responds but we aren't listening anymore. (See | |
13 | * https://github.com/systemd/systemd/issues/17421 for further information.) | |
14 | * | |
15 | * Note that we don't allocate any timer event source to clear up the graveyard once the socket's timeout is | |
16 | * reached. Instead we operate lazily: we close old entries when adding a new fd to the graveyard, or | |
17 | * whenever any code runs manager_socket_graveyard_process() — which the DNS transaction code does right | |
18 | * before allocating a new UDP socket. */ | |
19 | ||
20 | static SocketGraveyard* socket_graveyard_free(SocketGraveyard *g) { | |
21 | if (!g) | |
22 | return NULL; | |
23 | ||
24 | if (g->manager) { | |
25 | assert(g->manager->n_socket_graveyard > 0); | |
26 | g->manager->n_socket_graveyard--; | |
27 | ||
28 | if (g->manager->socket_graveyard_oldest == g) | |
29 | g->manager->socket_graveyard_oldest = g->graveyard_prev; | |
30 | ||
31 | LIST_REMOVE(graveyard, g->manager->socket_graveyard, g); | |
32 | ||
33 | assert((g->manager->n_socket_graveyard > 0) == !!g->manager->socket_graveyard); | |
34 | assert((g->manager->n_socket_graveyard > 0) == !!g->manager->socket_graveyard_oldest); | |
35 | } | |
36 | ||
37 | if (g->io_event_source) { | |
38 | log_debug("Closing graveyard socket fd %i", sd_event_source_get_io_fd(g->io_event_source)); | |
97935302 | 39 | sd_event_source_disable_unref(g->io_event_source); |
80710ade LP |
40 | } |
41 | ||
42 | return mfree(g); | |
43 | } | |
44 | ||
45 | DEFINE_TRIVIAL_CLEANUP_FUNC(SocketGraveyard*, socket_graveyard_free); | |
46 | ||
47 | void manager_socket_graveyard_process(Manager *m) { | |
48 | usec_t n = USEC_INFINITY; | |
49 | ||
50 | assert(m); | |
51 | ||
52 | while (m->socket_graveyard_oldest) { | |
53 | SocketGraveyard *g = m->socket_graveyard_oldest; | |
54 | ||
55 | if (n == USEC_INFINITY) | |
ba4e0427 | 56 | assert_se(sd_event_now(m->event, CLOCK_BOOTTIME, &n) >= 0); |
80710ade LP |
57 | |
58 | if (g->deadline > n) | |
59 | break; | |
60 | ||
61 | socket_graveyard_free(g); | |
62 | } | |
63 | } | |
64 | ||
65 | void manager_socket_graveyard_clear(Manager *m) { | |
66 | assert(m); | |
67 | ||
68 | while (m->socket_graveyard) | |
69 | socket_graveyard_free(m->socket_graveyard); | |
70 | } | |
71 | ||
72 | static int on_io_event(sd_event_source *s, int fd, uint32_t revents, void *userdata) { | |
99534007 | 73 | SocketGraveyard *g = ASSERT_PTR(userdata); |
80710ade LP |
74 | |
75 | /* An IO event happened on the graveyard fd. We don't actually care which event that is, and we don't | |
76 | * read any incoming packet off the socket. We just close the fd, that's enough to not trigger the | |
77 | * ICMP unreachable port event */ | |
78 | ||
79 | socket_graveyard_free(g); | |
80 | return 0; | |
81 | } | |
82 | ||
83 | static void manager_socket_graveyard_make_room(Manager *m) { | |
84 | assert(m); | |
85 | ||
86 | while (m->n_socket_graveyard >= SOCKET_GRAVEYARD_MAX) | |
87 | socket_graveyard_free(m->socket_graveyard_oldest); | |
88 | } | |
89 | ||
90 | int manager_add_socket_to_graveyard(Manager *m, int fd) { | |
91 | _cleanup_(socket_graveyard_freep) SocketGraveyard *g = NULL; | |
92 | int r; | |
93 | ||
94 | assert(m); | |
95 | assert(fd >= 0); | |
96 | ||
97 | manager_socket_graveyard_process(m); | |
98 | manager_socket_graveyard_make_room(m); | |
99 | ||
100 | g = new(SocketGraveyard, 1); | |
101 | if (!g) | |
102 | return log_oom(); | |
103 | ||
104 | *g = (SocketGraveyard) { | |
105 | .manager = m, | |
106 | }; | |
107 | ||
108 | LIST_PREPEND(graveyard, m->socket_graveyard, g); | |
109 | if (!m->socket_graveyard_oldest) | |
110 | m->socket_graveyard_oldest = g; | |
111 | ||
112 | m->n_socket_graveyard++; | |
113 | ||
ba4e0427 | 114 | assert_se(sd_event_now(m->event, CLOCK_BOOTTIME, &g->deadline) >= 0); |
80710ade LP |
115 | g->deadline += SOCKET_GRAVEYARD_USEC; |
116 | ||
117 | r = sd_event_add_io(m->event, &g->io_event_source, fd, EPOLLIN, on_io_event, g); | |
118 | if (r < 0) | |
119 | return log_error_errno(r, "Failed to create graveyard IO source: %m"); | |
120 | ||
121 | r = sd_event_source_set_io_fd_own(g->io_event_source, true); | |
122 | if (r < 0) | |
123 | return log_error_errno(r, "Failed to enable graveyard IO source fd ownership: %m"); | |
124 | ||
125 | (void) sd_event_source_set_description(g->io_event_source, "graveyard"); | |
126 | ||
127 | log_debug("Added socket %i to graveyard", fd); | |
128 | ||
129 | TAKE_PTR(g); | |
130 | return 0; | |
131 | } |